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Q: That all makes perfect sense, of course. However, one thing I've noticed is that, in a previous issue of one or two years ago, we provided a link to Angel Wings' excellent step-by-step photo tutorial on installing their Spit-Fire kit on a cruiser frame. I presume that most of our readership was exposed to that kit through that piece. Yet, until recently, when all those cheapo versions of the engines started showing up on eBay, we hadn't had one machine show up for our Gallery with that particular engine fitted. Since the eBay point, they've been coming in regularly.

Maybe that just means that our audience is more interested in looks and cheapness than actual function. This is a fairly safe bet, considering that most kustomizing treatments have a negative impact on bicycle performance; and I've seen some extremely junky donor bikes used as the basis for high-labor kustoms. The ironic thing is that the same people who start from cheap junk seem perfectly willing to then spend a giant wad of money on billet wheels and such to dress them up. People are strange, especially in this segment of the cycling demographic.

That said, I gotta admit that I fall into pretty much the same pattern, as, if I don't build it from scratch, which is theoretically sort of cheap, I think it's fun to start with something I find in the trash; and you hardly ever find a quality bike frame in the trash- if it's in the trash, it's usually because it started out that way, then got worse. Of course, I always replace all the mechanical bits with good stuff, but that's gotta be the most expensive way of ending up with a decent bicycle. Or car, for that matter.

Not to say there won't be demand for quality engine replacements after people get sucked in by the cheapo setups, but I have a sneaking suspicion that the big bucks in this activity will be made in selling expensive, quality-made dress-up parts to people who start out with those comparatively junky eBay engines.
Q: I suppose most people would think that it's crazy to consider making parts and accessories that would be easily more expensive than the engine itself. But, it seems to me that there really isn't that much out there in good-looking small engines made specifically for this purpose; and it sounds like when you get one of the good ones that it's worth a lot more than the price you pay for it. Tanaka (TAS) had a really nice-looking bike motor, at one time, pre-BikeBug:
http://bikerodnkustom3.homestead.com/gallery165.html and
http://www.bikerodnkustom3.homestead.com/gallery187.html 

But at the moment, these Chinese engines are pretty much it. I'm not considering the new Whizzers really, as they seem to be coasting on the original name, are ridiculously expensive for a Taiwanese repro, and seem to have their own quality-control issues, in spite of the high price.
Aftermarket clutch lever assembly by Pazzaz.
A: The problem with the carburetor is being addressed. A couple of different people are working on it. One guy is trying to make one out of steel tube.  Don Grube is having some cast with
The restrictions of the stock front engine and carburetor mounts are less problematic
when kustom frames are constructed around them, as in this clever but odd-looking solution by Firebikes' Sam McKay.
The factory carburetor mount is an alloy casting of fixed angle and position, which is quite restrictive on the type of frames suitable for mounting of these engines; to the extent that Spit-Fire has a set of fitting charts on their site. A more adjustable mount, as found on other engines, would allow greater fitting and angle options.
A: The way an expansion chamber works is, as the piston dumps the exhaust (the piston acts as a valve in a 2-stroke) the front cone of the expansion chamber allows the gases to expand and it has a sucking effect on the exhaust port. This also helps pull the fuel/air mix into the cylinder, and on out the exhaust port. The sound wave that comes out with the exhaust is bounced off the rear cone and back up the pipe where it crams that little extra fuel air mix that came out with the exhaust, back in the cylinder just before the piston comes up and blocks the port off. It is a supercharger in a way. That's why it's called a tuned pipe, as it's tuned to the rpm and how long the exhaust port is open. It's a nice little math problem if you like that sort of thing. But yes, the carb would have to be changed some to keep from fouling or burning up spark plugs. The carb is the same one for all the different displacement engines. The jet is replaceable, and I know a guy who has had some success drilling out the jet.

On that front mount, I have an idea for a billet thing that would fit most frames. But it would be huge and have sleeves to adapt it down. I don't see that looking any better than all the nuts and bolts. But it's worth keeping in mind. I'm sure something will be made that solves the problem. The rear mount is used to shim for the drive chain and is
movable and/or replaceable. I have seen a real nice billet piece that a guy did.  I've seen a set that allowed the engine to be offset to the side for a real wide rear tire. (O.C.C. Stingray)  It was pretty hacked up. The thing is, the guy got the engine in the frame.

Another thing someone was talking to me about is that a lot of guys are trying to put these engines in frames that it is impossible to get the carb on without cutting or bending the frame. So there are a lot of little things that could be made to help the kid or not-so-mechanical Dad who're bonding in the garage.
Coincidentally, I just discovered that DupliColor Metal Cast anodizing simulator spray-can paint. When I read the can and saw that it's rated to 500 degrees F, I immediately thought of Chinese bike engines. These are fairly attractive engines, and I think one would look great sprayed transparent red or whatever, with polished-off fin edges. Some nice chrome or stainless bolt heads or acorn nuts and some tasty billet parts, and you'd have something pretty snazzy, I think.

What's the story on the larger (60, 70, 80cc) displacement sizes?  Are the engines externally pretty much the same size and appearance? And is there as much difference in build quality as in the smaller ones?
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Fairly frequently, I run a search of eBay using the keywords "bicycle", "engine", and "motor", due to my philosophy that an engine is one of the coolest dress-up and performance accessories you can stick on a bicycle. In the past, I've run into quite a few kits this way, based on weed-whacker-style engines, and some classic motorbike repro setups, such as the Whizzer. Prices have generally been in the $400 neighborhood for the conversions, with the Whizzer kits starting at about $800. Lately, however, that search turns up dozens of people selling little purpose-built bicycle motorization kits made in China, starting at $150 or less, with displacements ranging from 48 CC up to a very interesting 80 CC, in 10 CC increments. Some of the listings are quite interesting, with all the new competition between sellers. In a recent search under this topic, I ran into a listing for a one-off billet air cleaner designed specifically for these engines.

"Aha!" I said to myself,  "Here's our kind of guy; and I'll bet he's fairly expert on the subject of these engines". Using the "Ask the seller a question" function, I contacted him about doing something on the subject with BR&K.

His name is Arlo Kraus, and indeed, he's our kind of guy, very knowledgeable on the subject, and he agreed to talk to us about these engine kits.

Q: Hi Arlo. I first noticed this type of Chinese bike engine on the Angel Wings site a few years ago, as the "Spit-Fire". But lately I've been seeing what looks superficially like the same engine kit all over eBay, at considerably lower prices. From the different sources bad-mouthing each other's wares, though, there seem to be some differences. What can you tell us about this; are they all the same basic design from different factories in China, or are they all from the same factory, with the bad-mouth comparisons just being made by fiercely-competing vendors?
A: There is a difference. There are a couple of dealers who are selling bad engines. They have become known as
"weak puppies" These are a run of engines that were manufactured in early 2004. The Spit-Fire and the StarFire 48cc square head had the exhaust ports cast in the wrong place, I understand they are cast 2mm. too high in the cylinder, and this caused a great loss of power. I also have heard that the intake runners are full of flashing from the casting process, and that causes problems also. The only cure is to install a 55cc hop-up kit that costs another $75. One of the dealers is still selling this engine and not telling the customers, in hopes they will never know the difference. I know my distributor (Star Fire) is not even selling these engines, unless he has installed the hop-up kit himself.
Arlo Kraus' typical stock Star Fire Gru-Bee 48 CC engine kit installation on cruiser frame.
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As I also understand it, there are six or seven factories in China that produce these engines. There are only two of the importers that have quality-control people in place at the factories,  that I know of, and even then there have been problems. I'm a dealer for Gru-Bee, and Don Grube lives in China, and he's at the factory almost every day. He has higher-quality bearings installed, that I've been told he gets from Europe. Some of the eBay sellers (not all of them) get their engines from whoever will sell them the cheapest. So the old adage of "you get what you pay for" is very much a part of these engines. 
I have had the pleasure of riding a bike with a Skyhawk Pico Wing-Ding and a Spit-Fire. I have to say the Pico has more power- in the 48CC-size engine.
Q: Gru-Bee? That answers another question I had. I was wondering if the Gru-Bee name was a reference to one of Art Clokey's Gumby TV films- the one about a little bee character called that, which built things really fast. I thought it was a pretty hip reference if that was the basis.
Arlo Kraus' billet air-cleaner cover for Chinese bike engine carburetors.
A: Ya! if you get two guys next to each other with shopping carts they're gonna race. The thing is, this hobby is somewhat new to mainstream America, so we really don't have guys lining up next to each other yet. But it's coming. The market is wide open for aftermarket products. There are a couple of guys who have been doing a little head milling and port polishing. But in a two-stroke engine this only gives the illusion of more speed, but it does increase power. The top end is mostly in the port timing, and that is built into the cylinder when it is cast. These are a cast aluminum cylinder with a flash chrome bore so they cannot be bored out or even honed. The cylinder head is cast real thin and supported with the fins, so even head work is something that is very limited, and needs to be done by a machine shop that can do very precise milling or you'll have a hole in your head, so to speak. I am a machinist by trade and have the ability to do this type of work. In fact, I have done one head and some port work
on an engine and I'm waiting on some guy to pull up next to me. But 'til then, I'm happy to putt around with a stock engine.

But custom billet accessories is a thing that I and some others have started doing. Right at the moment it's one-off parts by guys who just have to have it look kustom. That starts right after most guys take it out of the box. You know, I'm gonna use chrome bolts here and use this anodized or crinkle paint. That air cleaner and sprocket spacer I had on eBay was a test-market thing.  I'm working on some other top-secret things that I'm sure a lot of guys are going to want. But right now the market to sell these kind of things is so limited that it's not cost-effective to mass-produce. So it's real expensive to make. You have to imagine what the first guy to do a lowrider Stingray had to spend and hand-make. Just look at that market today.
Arlo Kraus' billet spacer for Chinese engine kit sprockets. It allows the use of a fatter tire.
Q: Yes, I can just imagine the work that went into building an OG lowrider bike- twisting that rod by hand, then having it polished and chromed, drilling all those extra holes in wheel hub flanges and rims, etc. That stuff took real dedication, back in the day.

My theory on these engines is that as soon as somebody starts making a lot of trick-out parts, these engines will become a lot more popular- especially once the factory chopper-style bicycles start hitting the streets in quantity. I'm sure that a lot of people buy Harleys just because all those goodies are available for dressing them up- kind of a grown-up Barbie doll deal for guys. Futzing around with them is easily as much fun as riding them, for this kind of folk.

Coincidentally, I just discovered that DupliColor Metal Cast anodizing simulator spray-can paint. When I read the can and saw that it's rated to 500 degrees F, I immediately thought of Chinese bike engines. These are fairly attractive engines, and I think one would look great sprayed transparent red or whatever, with polished-off fin edges. Some nice chrome or stainless bolt heads or acorn nuts and some tasty billet parts, and you'd have something pretty snazzy, I think.

What's the story on the larger (60, 70, 80cc) displacement sizes?  Are the engines externally pretty much the same size and appearance? And is there as much difference in build quality as in the smaller ones?
80CC Square Head engine, "blueprinted" and installed by Gary Newcomb.
A: OK, the 55cc hop up kit, 60, 70, and 80 CC engines, are all a larger displacement than is legally allowed, without a title, registration, insurance, safety inspection, and on and on and on. it makes your bicycle a constructed motorcycle in most states. So I cannot recommend that anybody install one on a bicycle frame. That being said, and guys being guys: they have the same dealer- versus-quality issues found in the smaller engines, sometimes more 'cause some think, since it's a larger engine, that less break-in time is required; or they just can't stand running at half throttle or less that long. And there go the bearings. The 80cc engines run at close to the same RPM but have a lot more power so you can gear them higher for more speed, or the same and carry a larger load.

To the average guy, the engines look the same. The 80cc is a little larger but I don't think you could tell it from a 48cc unless they were sitting on a table side by side. So a policeman isn't going to pull you over and say your engine's too big, unless you go by him at 50mph on a bicycle. By the way, most states say 30 mph is the max on a moped.  That is the law that most police would use to define your machine.
I think you're right about the hobby getting bigger when more kustom stuff is available. I'd like nothing more than to make things for these bikes and engines all day long. But at the present time the market just isn't there, it is picking up, but I just don't think I can feed the family off of it yet. I will say that some others and myself are getting some ideas and prototypes together and we will be slowly making more and more stuff
Q: You pretty much nailed the reason I was asking about the external differences in the bigger engines. I'm preparing to build a bike with a 1980 Honda Elsinore 250 CC motocross engine shoehorned into it. Nobody in law enforcement could possibly believe that mutant monster would be a street legal motorbike, but it's mostly a show bike anyway; although I might possibly go through the hassle of motorcycle registration, etc, if it's a lot of fun to ride.

But, with discretion, the speed potential of an 80cc engine would be there if you needed it. And it would be cool to have the knowledge that the potential's there. But yeah, if you do 60 in a 35 MPH zone on anything, you'll get nailed for it if you're spotted.

Kevin Waddle's polished Pico Wing-Ding 48 CC,  ported and polished internally, with high compression head
A lot of people say that bicycles can't handle high speeds. I went along with that, too, until I was researching gravity bikes a while back. They're all based on 20" BMX bikes, with the chain drive removed. In the advanced classes, the bikes are fitted with streamlined fairings and carry ballast for gravity to better work on. Those things are fairly routinely clocked at 80 MPH, I hear. And that's not with anything too out of the ordinary, as far as components go. Four-ply tires would be good, and they are available, and, of course suspension and really good brakes would be a good idea, too; but I'd think an 80 CC engine would be a fairly realistic power plant for a bike to run, if you kept a fairly low profile in your driving practices.
One performance aspect I've been wondering about is the stock exhaust system on these engines. It's a little bit dorky-looking, in my opinion, and a good place to start with aftermarket goodies. I've discovered, with this project, that modern 2-strokes, such as my Elsinore 250, make use of an exhaust expansion chamber, followed by a muffler, if they bother with silencing. In use, it functions as a sort of
supercharger, which acts by sucking, rather than blowing. And actually, the expansion chamber is so important to the function of the design that the Elsinore might barely run without it. Since they're so specific to the particular engine's characteristics I felt compelled to buy a stock pipe which will need considerable reconfiguring to work in my layout- without actually changing the lengths of the various elements.

Do the stock exhaust pipes incorporate an expansion chamber, and if not, would a properly-designed expansion chamber deliver a perceptible performance gain?
A: The speed potential of an 80cc, on a good day with the wind at your back, would be in the 45 mph range. Twice the horsepower does not produce twice the speed. But you're right, a person does have to show some respect for the law, If you're blasting through a school zone at the top end of a 48cc's range you couldn't stop in time to avoid hitting someone. Believe it or not, it probably takes twice as long to stop just putting at 15 or 20 mph; so being aware is all-important.

I live out in the desert between Tucson and Phoenix. It's not uncommon for the temperature to be 104* in the shade, and the asphalt has to be at least 150* at noon .So tires must be in good shape. I take a ride that is up hill for almost 15 miles. Of course it takes a while to get up there- probably 45 minutes to an hour. But coming down, I am doing 35 MPH in some places and this is a winding desert road. Brakes are a necessity. I adjust my brakes often. It's cool to go fast but ya gotta be able to stop.
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Arlo Kraus' "beater"/demonstrator based on Sears Free Spirit MTB frame.
As far as the frame being able to take the punishment of the higher speeds, I check mine every time I get off it. It takes some pretty good licks on these country roads where I live. I'm using an old
15-speed Free Spirit MTB frame that was laying out in the yard. I bought some cheap Wally World tires and tubes, Slime-filled, of course. This is my beater bike I let the kids use it and anybody that wants to take a test ride. It doesn't scare anybody that they may wreck it while test riding. Needless to say, it takes some pretty hard knocks, and keeps coming back for more. But this is a heavy-duty frame, wheels, bearings, and axles. I think that if someone is thinking of using a $79 cruiser bike as a frame to mount one of these engines on, that they should make sure the wheels, axles, and bearings are up to the abuse. Those downhill racers have the real high-dollar frames and a mile
of travel in their suspension, if I'm not mistaken; and if they weigh what I do, they don't need ballast. Most of the people that I've talked with do recommend 4-ply tires, and balancing your wheels for long high-speed (28mph)
highway use.

As far as this stock exhaust system goes, it's nothing more than a noise reducer and a way to keep the two-stroke oil off your pant leg. An expansion chamber is needed badly, even if it only worked a little bit, and it would look a lot better. And guess what one of those top-secret projects is? I'm working on the tooling to weld a few of these up right now. I worked up the numbers to make it a mid-range power pipe. So, it will be out there in not too long of a time. I don't think that it will make these little engines any faster, but they will increase the power output; and when you're dealing with 2 HP any increase is good. The cool factor goes up more than anything.  
Q: This being BR&K, the cool factor is naturally a high priority, but it's always nice to have that performance factor as a side benefit. You've mentioned that there isn't much of a market, at this point, for kustom parts for these engines. I also mentioned a while ago that chopper-style bicycles are about to be the big thing in the retail market here. This is in addition to our audience's being very involved in building their own choppers. This is shaping up to be a pretty heavy mass bike-style shift. Since most chopper bikes tend to look like motorcycles without engines, I'm convinced that these little engines are going to start to fill that void pretty quickly. Another factor is that the huge baby-boomer market segment, of which I'm a part, is starting to get a little creaky in the knees, and maybe lazier. I gotta admit, having some power assist is looking pretty attractive right about now. For guys like us, of course, that assistance pretty much has to not detract from the cool factor. Most of the auxiliary drive units out there are pretty dorky-looking, especially the ones which rub the front or rear tire. A system that drives a rear sprocket, like these Chinese kits, is easily twice as cool-looking, especially since the motor itself is sharper-looking than your typical weed-whacker mill, with the flywheel-blower shroud and all. Throw in the trick factor of kustom parts, and I think you might be feeding your family with it a lot sooner than you might think.

One slight style deficit I see is that the engine's integral mounting system is designed around the traditional English-style diamond frame, which has hardly been a major style in the US for maybe 20 years or longer. There are varying workaround adaptations everyone uses with other frames, but they all seem to look a little "nutsy-boltsy". Have you considered designing and producing a more substantial and cooler-looking front adapter mount?

A:  I'm gonna tell you, I think the mounting is an eyesore, but it works. There are so many different styles of frames and front down tubes, I'd need a warehouse just for front mounts. That is one of the first things that is asked by most every body that's building their first bike. What do I do with this front mount? One of the dealers has a design for a generic "kinda fits all", but even it's got a lot of nuts and bolts. I have a couple of ideas for the bike that I'm building right now, but it wouldn't fit anything except the frame I'm building. Of course these are generic little engines and they have to be massaged into most bikes. That's kinda what makes them fun. If everybody had the same mount that worked on every bike, I'd have to have something different. The guys that are building these bikes like to tinker; in fact if you don't like to adjust and tinker on your machine, this isn't your kinda hobby. These are a perfect platform for the
back-yard engineer. I think that is where you will see the most ideas come from.
I think you're right about the major change of bike styles, and this engine is perfect for it. The mid-frame location and chain drive make a cool set up on a plain-Jane stock bike, but you throw in the chopper look, and it's a gotta-have. The engines that mount on the fork or over the rear wheel have that "I added an engine and I don't care what it looks like", kind of feel to me. If I just wanted an engine I'd ride my Harley. These have
coolness written all over them.

I was riding on my little moto a couple days ago, and a guy on a brand-new 2004 Triumph had me pull over so he could check out my 10-year-old MTN bike with this really cool engine. I tell you, this guy was ga-ga.  What's that say about these little engines?

You mentioned Baby boomers. We did a little poll the other day on one of the message boards about the average age of the person that owns one of these bikes. It seems that the average kid was 47.  I'm on the high side of the average, overweight, and don't care. The more assist I get the better.
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Factory front engine mount, designed for use on diamond frames is fairly sanitary.
Use of them on other frame designs is more
problematic. Inset is Arlo Kraus' mount adapter for a cruiser frame.
Q: I don't think I remember the details of your specific front mount, and I wouldn't call most of the ones I've seen eyesores, anyway. But they all seem to have that "Erector Set" look about them, which clashes a bit with the design of the engine as a whole. I'd think, considering the expanding market for them, that both the front and rear mounts could be modified in the casting dies by one of the more quality-oriented factories. Something that allowed a bit of flexibility in the mounts, without being quite so nutsy-boltsy seems conceivable to me.

And you're certainly right, that as things are now, most of the people building the bikes around these engines tend to be mature gadgeteer types who have been around long enough to have developed the skills and perseverance to like messing around with the setup. But, as these things catch on with the larger market, kids and "nimrod" adults are going to need or demand less futzing to achieve the end product. Of course, this could result in a whole cottage industry deal, in which gadgeteer types specialize in building motorized turnkey machines based on specific frames. Come to think of it, both Firebikes and JAKZ seem to be leaning in that direction.

Getting back to an earlier topic- expansion chambers: It occurred to me today that the use of an expansion chamber- which in effect is the rough equivalent of supercharging, would probably call for differences in the carburetion. Are the carbs on these things capable of producing a greater fuel/air volume on the intake side? Sorry if I've just blown something else on your secret project list.
A: The way an expansion chamber works is, as the piston dumps the exhaust (the piston acts as a valve in a 2-stroke) the front cone of the expansion chamber allows the gases to expand and it has a sucking effect on the exhaust port. This also helps pull the fuel/air mix into the cylinder, and on out the exhaust port. The sound wave that comes out with the exhaust is bounced off the rear cone and back up the pipe where it crams that little extra fuel air mix that came out with the exhaust, back in the cylinder just before the piston comes up and blocks the port off. It is a supercharger in a way. That's why it's called a tuned pipe, as it's tuned to the rpm and how long the exhaust port is open. It's a nice little math problem if you like that sort of thing. But yes, the carb would have to be changed some to keep from fouling or burning up spark plugs. The carb is the same one for all the different displacement engines. The jet is replaceable, and I know a guy who has had some success drilling out the jet.

On that front mount, I have an idea for a billet thing that would fit most frames. But it would be huge and have sleeves to adapt it down. I don't see that looking any better than all the nuts and bolts. But it's worth keeping in mind. I'm sure something will be made that solves the problem. The rear mount is used to shim for the drive chain and is
movable and/or replaceable. I have seen a real nice billet piece that a guy did.  I've seen a set that allowed the engine to be offset to the side for a real wide rear tire. (O.C.C. Stingray)  It was pretty hacked up. The thing is, the guy got the engine in the frame.

Another thing someone was talking to me about is that a lot of guys are trying to put these engines in frames that it is impossible to get the carb on without cutting or bending the frame. So there are a lot of little things that could be made to help the kid or not-so-mechanical Dad who're bonding in the garage.
It's my understanding that trying to get the Chinese to change anything is next to impossible.  After all, these engines are tools to them, not toys. That's why they don't make any hop-up stuff. These are made for Joe Factory Worker to save up for a year, to be able to buy one for the bike he's been riding to work for ten years. To them, it ain't broke so they're not gonna fix it.

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The factory carburetor mount is an alloy casting of fixed angle and position, which is quite restrictive on the type of frames suitable for mounting of these engines; to the extent that Spit-Fire has a set of fitting charts on their site. A more adjustable mount, as found on other engines, would allow greater fitting and angle options.
Q: I'm not so sure that still applies. Even before the recent capitalism explosion over there, the government was discouraging bicycle transport, due to the congestion of the roads and streets by everyone being on bikes. The government was encouraging/ordering everyone to use public trains and buses instead. Then the boom of entrepreneurship took off. As a result of this, a huge number of Chinese were suddenly bringing in fairly decent money for a change. According to reports I've seen, so many Chinese have already bought cars for personal transport that it's having a negative
impact on the air quality of our west coast. And it's safe to assume that the trend will continue. With the Chinese domestic bicycle market in a downward trend, at a time when the American export market is booming for, among other things, bicycle motors, my feeling is that the American market will be of increasing importance to almost every segment of bike manufacturing over there. This should mean that American desires will be catered to, much more than in the past. Somebody just has to tell them what's wanted, and sign a contract to buy them.

I have a strong feeling that the junky motors coming from China at this point are only being sold to the lowball-price American importers you mentioned earlier. After all, those Chinese who still need that sort of thing need them to be reasonably well-made and reliable.

We have a family member who's a partner in a manufacturing brokerage over there. He's told me that he can get just about anything made, at any quality level the buyer would be willing to pay for. As an example, if you need a titanium knee joint installed right now, it will probably have been made in a Chinese factory and marked up about 1000% by the time it's installed in you.

The conclusion I draw from this is that someone who's not content with just buying a container full of off-the-shelf stuff at the lowest price possible can come up with a really amazing quality product from China that Americans, or anybody else, will pay serious money for; and that especially applies to things like bike engines.

A couple of months ago, I visited a friend in the Baton Rouge area. In his garage, mounted in a test stand was a new Chinese-made 90 CC 4-stroke engine with a 4-speed gearbox, electric starter/generator, and all the usual bells and whistles. It was basically a clone of a Honda ATV engine from the '70s, and it was beautifully made and ran like a top. He'd bought it for about $180 from an eBay seller. It sure made me think.
I ran into that carburetor accommodation problem you were talking about during that same research session in which I spotted your billet air cleaner. I'd just finished a new frame for a bike I was building for myself, not thinking at the time about motorizing it. While looking at all those cute little inexpensive engine kits, I started thinking that it would be pretty cool to get one for mounting on my new chopper. Unfortunately, the combination of the existing motor mounts and the carburetor placement made it impossible to fit one to that particular frame, without pretty much starting from scratch. What are the possibilities for an adjustable adapter to re-position the carburetors on these engines? Seems to me that would be a popular item, too.
The restrictions of the stock front engine and carburetor mounts are less problematic
when kustom frames are constructed around them, as in this clever but odd-looking solution by Firebikes' Sam McKay.
A: The problem with the carburetor is being addressed. A couple of different people are working on it. One guy is trying to make one out of steel tube.  Don Grube is having some cast with
a 45* angle at the end so the carb sits to the left side of the top tube. I think he's getting it done at a different factory. That's what he does to have special things for his kits, like the 9-hole sprockets and upgraded throttle assembly.

The thing about getting the engine manufacturers to change something is they want to make a cargo ship-full before they will change anything. They were approached about doing a sheet-metal expansion chamber, and they didn't want to deal with the engineering or tooling. They would do it if someone brought the dies and had the bugs all worked out. So, like I've been saying, the market is wide open right now. I think this is a good thing, as we will be able to see what people want a little at a time. Then we will be able to outsource it, as they say.
Q: You've verified that there's a range of quality in these engines, and your mention of the 9-hole sprocket reminded me of something else I was wondering about. (For the sake of our readers' edification, some kits come with 5-hole sprockets, which aren't as compatible with the most common American wheel pattern- 36 spokes, whereas 9 holes for mounting to the spokes don't require distorting the spoke pattern.) How much quality and appearance disparity is there in the steel parts that come with these kits- plating quality and such?
A: I've only seen, in person, the Pico SkyHawk and the Spit-Fire. The steel chrome parts of both have a very good appearance. I've seen the ads for some of the others that you can see the copper through the chrome in the photo. Some of the guys that have gotten a chrome tank say it gets rusty just sitting out at night. So, I'm sure it's like all the rest of the cheaper kits, even the chrome is thin. The cheaper kits come with that 5-hole sprocket also, that is for the Chinese bikes, as they have 40 spokes in the rear wheel.  The 9-hole sprocket also works on a 72-spoke wheel, with smaller bolts to clear the smaller spoke clearance.
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9-hole sprocket mounted on 36-spoke wheel.
Q: How well does that mounting the sprocket to the spokes of the wheel work? Does that put a lot of stress on the spokes, or is the torque distributed pretty evenly?

A: The 9-hole sprocket is real easy to install. At the most, it needs a little bit of material taken out of the center; just the chrome is enough to get it to register on the hub. Getting the rubber spacer and all the nuts and bolts in place takes a little cussing, but once you get the right words, it seems to slide right together. The 5-hole, though, is a different story altogether. The first thing is, it's real small in the center and requires some machine work, or a whole lot of filing to fit on most American bikes. Then it only has 5 holes, so there is a lot of spoke interference, and that leads to broken spokes. The 9-hole, on the other hand, has no spoke interference.

The instructions in the kits that I have say to upgrade your spokes to 10 or 12 gauge, but I'm over 275 lbs. and have had no problems. The sprocket's load is spread out over all the spokes on the left side of the wheel; it uses a thick piece of rubber sandwiched into the spokes between the sprocket and a 2-piece steel backer. There is a torque value for the bolts to keep the pressure even. It also keeps the sprocket running true.
Q: That sounds pretty well worked out.

One very desirable thing about these engines, to me, is that they have a manually-actuated clutch. It's almost impossible, when doing a home-brew motorizing project, to find a non-centrifugal clutch. Most of the non-Chinese motorizing kits have a typical pull-start arrangement with a blower flywheel inside a shroud. I suppose this is fine for a leaf blower or a lawn mower, but who wants that kind of deal on a motor vehicle? And, unless you use a spring-loaded tire-roller drive with a release lever, which is a crude sort of clutch, you're stuck with having to use a centrifugal clutch, because there doesn't seem to be any other kind available for use with small engines.

How are these clutches as far as function goes? Do they work pretty well?
A: The clutch on these engines is a pretty well thought-out design. They work very well for what they are intended to do; but they are not made to pull you away from a dead stop. It requires a couple of pedal strokes (two or three) to get a little motion going before letting the clutch out. The clutch is also used to start the engine, by pedaling up a little speed and dropping the clutch to spin up the engine.

The clutch lever has a lock lever built in, to keep the clutch disengaged 'til you're ready. It's kinda cheesy and some guys just break it off right away. I like to use it at stops, and it's handy for moving the bike around the shop. You have to keep in mind this is a bicycle with an engine mounted on it, not a motorcycle. I try to revert back to bicycle operation well before a stop so I can use both front and rear brakes. As I said before, it takes quite a bit longer to stop.
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Aftermarket clutch lever assembly by Pazzaz.
Some of the cheaper kits come with a very cheap clutch cable that stretches and is very hard to keep adjusted. The higher-quality kits have a real nice cable and, once adjusted, seem to require very little attention, other than the basic maintenance.

Engines sold in some Provinces of Canada are required to have a centrifugal clutch. So the Road Runner brand (Spit Fire Canada)
has a pull start and a centrifugal clutch.

Q: Sounds like the latching clutch lever's another good candidate for kustom billet treatment, or at least an improved and more substantial design in a cast-and- polished item.

A lot of our readers would be using their moto bikes in urban traffic situations. In that environment, standing-start acceleration is a pretty important performance aspect, since pulling out into Manhattan traffic, as I'd be doing if I had one, requires getting up to traffic speed in a hurry, to avoid being smeared by crazed taxi drivers. In such a situation, top end isn't as important as low end. If somebody had a larger rear sprocket fitted to their machine, would this help the clutch's performance without the need for that relatively-slow pedalling startup? And is there such a sprocket option in existance at this point? If not, is there any reason why there couldn't be?
A: There are a few different sprockets available, from 55 tooth to 36 tooth. Most are in the 5-hole pattern, with two or three different ratios in the 9 hole. The front sprocket comes only as a 10 tooth.

The clutch is a single dry disk type; it's just not made to slip as you accelerate. You only have to pedal 2 or 3 strokes and then you will out-accelerate any bicycle.
Q: I suppose most people would think that it's crazy to consider making parts and accessories that would be easily more expensive than the engine itself. But, it seems to me that there really isn't that much out there in good-looking small engines made specifically for this purpose; and it sounds like when you get one of the good ones that it's worth a lot more than the price you pay for it. Tanaka (TAS) had a really nice-looking bike motor, at one time, pre-BikeBug:
http://bikerodnkustom3.homestead.com/gallery165.html and
http://www.bikerodnkustom3.homestead.com/gallery187.html 

But at the moment, these Chinese engines are pretty much it. I'm not considering the new Whizzers really, as they seem to be coasting on the original name, are ridiculously expensive for a Taiwanese repro, and seem to have their own quality-control issues, in spite of the high price.
It would be really idiotic to put a lot of money into performance enhancements for the 48 CC version of these engines, since the larger-displacement versions are hardly any more expensive anyway; so I imagine that cosmetic accessories make a lot more marketing sense. Would you care to share any other ideas you have for potential dress-up accessories?
A: You know, it is easy to spend more on cosmetics than the original engine cost on a car or motorcycle. It happens every day. I don't see this hobby being any different. I was out for a ride this morning and had an idea for a finned exhaust flange like on the old Triumphs and BSAs. It would have no purpose at all- it would just look killer. So I'll probably be making one in the next week or two. I also will be doing a cover for the clutch and reduction-gear case. It does reduce the noise from the straight-cut gears- they get to singing pretty good on a long easy upgrade. I'm also drawing a jackshaft set up that will be easy, cheap and look good. In fact I'm looking for the best buy on the parts right now..
Arlo Kraus' billet finned exhaust flange. Upon reflection, I've decided that the reason for this on the original British motorcycles was that it functions as an air-cooled heat sink, to prevent heat blueing of the header pipe's chrome plating.
The Whizzer you mentioned is a nice looking rig; it's just too expensive and limited in its use, as a base for a kustom tricked-out bicycle. For what you pay for it, you would have a hard time taking the cutoff wheel and torch to it. With these little Chinese engines, the way they can be shoe-horned into almost any frame, it's a real inexpensive basis to play with. And the accessories can be added as you can afford them. Someone said they had finished their moto bike the other day, and I wondered if you ever really finish one of these.

Q: I've sure never finished anything like that, as long as I've still had it around to look at. That's a great idea about the finned exhaust flange. I always loved the look of that thing on the Brit motorcycles. I wonder if it had any real function on them, now that you mention it. I guess I always assumed it was for use in screwing it off and on, or something. Thinking about it, though, that doesn't make a
lot of sense. That clutch/gear case cover sounds great, too; especially if you're thinking ball-milled grooves or cast and polished ribs. Can't get too much of that stuff.
If I know our readers, by this time they're probably wondering about pricing. The prices of these engines are all over the place on eBay; which is understandable from what you've told us about the quality range. If someone wanted to buy one of the good-quality 48cc engine kits, from a reputable dealer, such as yourself, how much should they expect to pay for it? And what's the going price for a good 80cc one? I'm presuming that our kind of audience, if they wanted more performance than the street-legal one delivers, would go for the max, and skip the in-between displacements.
Visual comparison of stock 48 CC engine (above) and same engine fitted with Arlo Kraus' trick-out parts, including billet gear/ clutch case cover (below). The coolness difference is obviously considerable
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A: My price for a Pico Wing-Ding f50 48 CC is $350 plus shipping,  $450 plus shipping for the 80cc and the 60cc is $375 plus shipping. I have a 90-day day warranty, from the day it's received, and full support from the factory.

Q: I assumed there was going to be a price differential between the vendors selling trash, at $135 per kit, and the others, but this is a bigger jump than I would have extrapolated.

But, like the guy said, "There Ain't No Such Thing As A Free Lunch". However, $350 is serious money, and I'm not sure that our audience would see that as a "giggle" investment. $450 for the 80cc units seems a bit more likely, for some reason, maybe the hot-rod thing; Although that's still a fairly hefty price tag.

A: The Angel Wings Spit-Fire sells for $350 (it's listed at $425) and only comes in the square head 48cc.

Any thing that is selling for $135 is damaged. A guy was selling from a pallet that got crushed in shipping.

Would you buy a swap-meet no-name bike to use as the base for a custom streched limo and replace all the bearings, axles, wheels, seat, and handle bars? I don't think so You'd buy the best frame you could afford and build on that 'cause you know you're not going to have to replace it .If there is a problem you know that the dearer will stand behind his product.

On the shipping thing I only charge what UPS charges me. I don't make another $20 off the fact that it must be shipped .A lot of things sold on ebay have the shipping charge jacked up to almost what the product cost the vendor. I ordered a set of saddle bags for my Sportster on ebay with the Buy it now option for $45. When I got the bill on Pay Pal the shipping was $96. Of course trying to contact the vendor to cancel the purchase was next to impossible. I guess I was trying to get more than I was paying for. 

Most of the eBay engines are selling for $180-$200 plus $45 shipping. They come with a 5-hole sprocket that will require a ton of filing or taken to a machine shop. That's $25 minimum. More than likely you'll get a weak engine, 'cause that's mostly what they're selling along with the factory rebuilds. (These are the ones that are painted silver)  So you ship it back for $25; he puts it on a test stand and it starts for him, so he sends it back and tells you it'll get better after it's broken in; of course it doesn't, and as I said before, the only fix is a $75 plus shipping for the hop-up kit. And it still doesn't run as well as the Pico Wing Ding. Then there is the clutch cable and the plastic throttle that has to be replaced before you can even start, for $25. Most don't have any kind of instructions in the kits and if they do, they are in Chinese. And since you bought it on eBay, there's no one you can call and ask how it goes together. Even if you skate by the normal problems with these engine, and all you need is an exhaust gasket or a carb kit, where you gonna get it from? Most ebay sellers don't sell repair parts. I'll say it again; you get what you pay for.
Q: That all makes perfect sense, of course. However, one thing I've noticed is that, in a previous issue of one or two years ago, we provided a link to Angel Wings' excellent step-by-step photo tutorial on installing their Spit-Fire kit on a cruiser frame. I presume that most of our readership was exposed to that kit through that piece. Yet, until recently, when all those cheapo versions of the engines started showing up on eBay, we hadn't had one machine show up for our Gallery with that particular engine fitted. Since the eBay point, they've been coming in regularly.

Maybe that just means that our audience is more interested in looks and cheapness than actual function. This is a fairly safe bet, considering that most kustomizing treatments have a negative impact on bicycle performance; and I've seen some extremely junky donor bikes used as the basis for high-labor kustoms. The ironic thing is that the same people who start from cheap junk seem perfectly willing to then spend a giant wad of money on billet wheels and such to dress them up. People are strange, especially in this segment of the cycling demographic.

That said, I gotta admit that I fall into pretty much the same pattern, as, if I don't build it from scratch, which is theoretically sort of cheap, I think it's fun to start with something I find in the trash; and you hardly ever find a quality bike frame in the trash- if it's in the trash, it's usually because it started out that way, then got worse. Of course, I always replace all the mechanical bits with good stuff, but that's gotta be the most expensive way of ending up with a decent bicycle. Or car, for that matter.

Not to say there won't be demand for quality engine replacements after people get sucked in by the cheapo setups, but I have a sneaking suspicion that the big bucks in this activity will be made in selling expensive, quality-made dress-up parts to people who start out with those comparatively junky eBay engines.
Well, Arlo, sounds like we'll be seeing some interesting stuff coming out of your shop in the future. As these engines become as widely popular as I imagine they will, I think you'll find that there'll be some heavy demand for goodies for them.

I'm really glad you were willing to share your information and insights on these engines, and their possibilities. It's really good that our readers can get the lowdown from an expert on them before they shell out their money on the first eBay listing they run into. I imagine it would be a real turn-off to end up with one of those "weak puppies"; whereas starting off with a good one would be pretty addictive. Jeeze, I'm almost addicted, and I don't even have one (yet). I guess I'll have to start work on another bike pretty soon, after I (sort-of) finish the current one.

Thanks very much; and please be sure and keep us posted on your activities.
A: Thanks for the opportunity to share what I know about a great hobby, I hope you and your readers will be able to use these thoughts and ideas to make a better decision, if you're thinking of buying one of these engines. I've had a great time doing this.

Post Script: As usual, Arlo's interview was conducted several months before this issue went up. I usually do a last-minute run-through with the interview subject, to see if the information's still current. This time, along with some more recent photos, I received the following new information from Arlo.

Arlo: Something else: Since we did the interview, there has been a lot of new stuff coming out. There is now a jet set that allows you to adjust the carburetor; there are wheels with the sprocket holes in the hub, and front drum brakes. There's even an expansion chamber from a small motorcycle, which has been adapted, and is available now. So, as you said, the engines are starting to take off with kustom moto builders.

Jim: And something I've noticed lately, on eBay, is that vendors are starting to offer "bare-block" replacement Gru-Bee 55 CC "hop-up" engines, which can be used as drop-in replacements by people who started out with the "weak puppy" kits Arlo was referring to in his interview, which sort-of verifies another theory.
I suppose a good automotive analogy would be the VW Beetle engine. They're common, dirt cheap and really popular with builders for that reason; so there's a world of hot rod and trick-out parts available for them, making it possible to spend a lot more on the accessorization and enhancement than you'd spend on the basic engine.

Yes, 30 MPH is pretty fast for a bicycle, and most people would be perfectly happy with that. But people who carry the hot-rod gene always want to make it faster, louder, and more interesting. And in many cases, such as yours, they want it to be trick-er too, preferably with billet alloy parts and chrome. That billet air cleaner cover of yours is really nice-looking, and your sprocket spacer to allow fatter tires looks good, too. What other aspects of the engines lend themselves to trick or performance parts, and do you plan to make them, at least for yourself?
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