My First Motorbike Project

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gera229

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So far I have been researching and reading on the forums and decided that I will go with a pocket bike motor with a stage 2 kit.
I have yet decided whether I want it inframe or in the back and whether I want chain or belt drive.
My goal is acceleration and power and read that this engine is more powerful than the motorbike 66cc/80cc engines and runs smoother as well as revs higher. It uses a centrifugal clutch.


Ordered:
Engine stage 2 kit
90mm bolts from mcmaster carr

Here is what I have to order or buy from a local store:
Copper head gaskets
Exhaust
NGK spark plug
Fuel line (Should I get this from pocketbikeparts.com? $15 is it worth it?)
Fuel Filter
Throttle handle
Sprocket and chain. (Idk what sprocket and if they will fit the bikes and so).
OR belt drive and gear

Should I buy a complete mounting kit ready or should I make one? (I'm trying to go for the cheaper rout, maybe if a completed one is cheap then I may reconsider that route)

I'm buying a used mountain or road bike. I can get a diamond back for about $100 used.

I have a local Low's and Home Depot near me. Also have a few hardware and metal sheet stores around.

Let me know if I am missing any parts here. And give me suggestions.
 
lowracer

lowracer

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Gera229,
If you go chain drive, you'll need reduction (jackshaft or transmission) since I dont think anyone makes a huge sprocket for cheap.
You can mount the pocket bike engine either by using the 4 holes around the clutch (like a friction drive kit) or using the 6 holes under the engine (which is how I like to mount them). Dont spend $15 for fuel line Dax sells it for way less. The exhaust is another eBay item for around $40. You will probably need some flex pipe unless you can bend & weld yourself a nice piece of conduit. Copper head gaskets are at PocketBikeParts.com for 1.99/ea. The fuel filters I got from ACE hardware or an auto parts store for cheap. I use a brake lever as my throttle...works great. NGK spark plug on eBay too. Aluminum or steel stock from Lowes (1/4" if going aluminum) to build the rack/motor mount. As far as buying the bike, this is personal opinion...I would go heavy duty like a DH MTB with a triple clamp fork (if I had to do it all over again & start from scratch.) The no-suspension bikes are good for cruising around slow, but not what this pocketbike engine is capable of. A front shock is good, but again for high speed, all the time, I'd go find a used Downhill MTB that wasn't used for huge drops. I've seen used Rocky Mountain RM7's for like $500-$600 on eBay in the past...Thats what I got & would definitely get another or something similar...The more monstrous the better...With disc brakes & lots of suspension...
-Lowracer-
 
lowracer

lowracer

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Gera229,
You gotta get the gearing correct or you wont get it to run in its powerband & it will stink! I heard another member using one of these engines geared all wrong & he felt it was a dog.
I did some experimenting with gearing changes on mine & tried a 1.75" engine pulley instead of my usual 1.5". The engine never got 'on the pipe' & felt like someone swapped engine on me while I wasn't looking...lol
For my flat land riding, & my bodyweight (Welterweight) 15.6:1 works well for quick enough acceleration, great mid range throttle roll-ons & ludicrous speed up top.
-Lowracer-
 
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gera229

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I weigh 200 and plan on getting a bike used off of craigslist that might not have suspensions. I live in the streets where a lot of people/ police may be so I might not even ride as fast as it's capable of due to that.

As far as reduction goes, how do you suggest I make the reduction if I build a bike inframe kit?

When I get all my parts I will do some brainstorming and drawings.

Also China Girls have an inframe reduction kit and these Stage 2 engines are more powerful. Would these stage 2 engines still be more powerful than the 66cc/ 80cc china girls with a reduction kit (Or does a reduction kit increase power already thus making it even more powerful?)?
Or if I asked the opposite: Which would be more powerful if lets just say that the China girls did not have a reduction kit - so neither of the engines have a reduction kit now, the stage 2 engine or the China girl 80cc?

I am concerned about power a lot in making my decision on which engine. Even though I already placed my order on the stage 2 engine I am still curious.
 
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lowracer

lowracer

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For your type of riding & area & bike selection, I wouldn't get a Pocket bike engine (loud w/ lots of horsepower). The pocketbike stage 2 engine is alot more potent than a China girl. Reduction doesnt have anything to do with power of the engine. Gearing & getting it correct are key to any engine especially when running only one ratio. I dont build using in-frame or chain drive, but if I had to I'd probably do a DIY small jackshaft using a bicycle bottom bracket & 2 right crankarms (the one with the chainrings) one on each side. You should check out Sick Bike Parts & their neat gearing setup for shifting gears on an MB.
-lowracer-
 
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gera229

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How loud it is does not bother me. If law permits it then I should have no problem in CA.
As far as power goes, so the stage 2 engine is a lot more powerful and has a lot more power than all China girl 80cc engines. Correct me if I am wrong.

Now, will it run quieter or louder than the china girl at 30 mph using only half it's power compared to a China girl running 30 mph at it's max rev and power?

By the way I have no clue what you said in the last part LOL. First of all I do not know what a jackshaft is nor what crank arms are. :). I should look it up.
 
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lowracer

lowracer

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I probably shouldn't have said its too loud...At 30 mph its not loud at all. In a way, if you dont fell the need for speed all the time you can get very high gas mileage from a Pocket bike engine...I logged 152 mpg taking it easy. Its just that its got such an addictive top end, I find myself always wanting to floor it...lol
If you go chain drive, you are going to need to research jackshafts & gear reduction. I solved the gear dilemma going belt drive & using a huge rim sized pulley...I like things simple.
-Lowracer-
 
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gera229

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Yeah I would like the engine with more power. The stage 2 engine is a lot more powerful and has a lot more power than all china girl 80cc engines (Correct me if I am wrong.) PLUS it's more reliable. That makes a big difference and sounds like a killer deal for the money you pay for it when compared to all China Girl 80cc engines.

I might get a belt drive on the rear wheel. I always thought your belt drive setup will only work on the front wheel, but then I actually thought again and looks like your bike's rear part isn't the same as it is on other bikes due to the mono shock there.
 
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lowracer

lowracer

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I made my own racks for both the Pocketbike engine bikes (& a few others). I do however own a BMP friction drive kit that I bought & still use on a 3rd MB just for slow riding with my daughter (has 2 seats). If you are not too mechanically inclined, I would recommend just buying a kit & hooking it up (Dax friction drive for $149). Then you would only need a fuel tank & exhaust (Dax sells the fuel tanks for $15 & fuel line). The friction drive kit also solves the gearing problem you are going to run into if you want to go chain drive (its ready to roll w/1.25" roller).
-Lowracer-
 
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gera229

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I actually like solving problems, just on a limited budget. I don't want friction drive for sure.

I am still trying to figure out how I will mount the sprocket or whatever on the wheel of my bike.
 
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lowracer

lowracer

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DIY (Doing it yourself) is definitely a rewarding experience especially when it turns out well. Though $149 for a kit seems steep, I guarantee I've spent more on each little piece ordered with shipping costs & running back & forth to Lowes or ACE Hardware in gas money & the time it takes building the drive systems myself...
Don't get me wrong, I'd do it again (DIY) in a hearbeat & may tackle a twin engine bike project in the near future. But $149 on a ready to go system is cheap.
-Lowracer-
 
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gera229

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Update: I just realized that the inframe kit with chain drive will just not work. The motor has to be in the rear because for the inframe to work you need to turn the motor upside down due to the direction in which it spins and I do not think that will be good for the motor.

If you know anyone who did an inframe kit I will be glad to know.
 
MotorBicycleRacing

MotorBicycleRacing

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gera229 said:
Update: I just realized that the inframe kit with chain drive will just not work. The motor has to be in the rear because for the inframe to work you need to turn the motor upside down due to the direction in which it spins and I do not think that will be good for the motor.

If you know anyone who did an inframe kit I will be glad to know.
Click to expand...
2 stroke motors can be mounted in any direction as long as
the carb float bowl is fairly level.
If you use a pumper type diaphragm carb you can mount in any
direction just like a weed wacker.

Anyway the motor does not have to be turned upside down.
Try looking at a pic of a pocket bike which have the engines in frame
like a motorcycle.

I have seen a pocket bike motor mounted in frame using a cheap
chain drive gearbox and the motor mounts with the carb
in the back and the sprocket on the left with CCW rotation.


 
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gera229

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Is that your bike?

If so, is the engine small enough so that it does not touch the legs?

Also, how would I fit the sprockets on the wheel?
 
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MotorBicycleRacing

MotorBicycleRacing

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gera229

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What I wonder is this:
Will I need to use a pocket bike sprocket
Or can I use one of the motorized bicycle sprockets?
 
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