My Mini-Chopper Build!!!

[thgrahamjr]

Well I'm working on converting a chopper style bicycle into a 49cc 2 stroke Mini-Chopper, I have salvaged some parts from an older pocket bike (e.g. brake disc, mechanical calipers, 2 stroke motor and all the components from the handle bars). Here are some pics of my progress, all comments or questions are welcomed.

[Do Work]

Hey thats a sweet frame to start with. Looks like it will be a screamer. Are you going to run a belt drive or chain? Keep pics updated.

[thgrahamjr]

It will be chain driven

[tykenfitz]

how are you going to attach the sprocket or pulley to the bike wheel? Or will you be using a different wheel? Also, how are you thinking of mounting the engine? Looks good.

[thgrahamjr]

I'm not sure about the sprocket yet, I have to get it and then I'll figure it out but I will be sure to feel everyone in and have pics. As for the motor this is how I am mounting it (pic below), of course it will look bigger in reality.

[Raywelder]

This will be a cool build for sure.

[thgrahamjr]

I will definetly post pics along the way, was at the hardware store today and picked up a 6" x 16" 16ga plate to make the motor mount.

[thgrahamjr]

Well I worked on the motor mount today and got it welded in and then :oops: , I forgot about putting the carb back on when I test fitted it so now I have to cut a slot for the bowl of the carb to fit in :furious2: But it still looks good, here are some pics. Comments and suggestions welcomed.

[Raywelder]

Looking good!

[oscaryu1]

How'd you make those holes... longwise? I never knew :(

[Raywelder]

How'd you make those holes... longwise? I never knew :(

You drill two holes and cut the slot out with a jigsaw.

[thgrahamjr]

I layed it out and drilled two holes (one on each end of slot) and then cut the centers out with a grinder with a cut-off disc.

[thgrahamjr]

I got the slot cut for the carb and put the carb on to see what it looks like, here are a couple of pics.

[Moto909]

that engine is exactly the same as what a kid in my metals class is using. he is making a scooter with it.

[thgrahamjr]

Oh yeah? Cool....It is a 47cc 2 stroke engine off a pocket bike.

[oscaryu1]

If you're looking for performance, that stock carb doesn't do much.

[SpyGuy]

Fix that pipe or buy one. The pocketbike engines need to have that expansion chamber for good tuning. You may also be able to run the pipe back under the engine instead of over it, as in the usual pb setup. I would suggest a heavy-duty clutch while you're at it.

The stock carburetor is probably one of the best carbs for the bike if set up correctly. New main jet, ported exhaust, better reeds, performance air cleaner with velocity stack ... the stock carburetor can even be race-ported for better air flow by drilling completely through the mouth of the carb with a 1/2" drill (you gotta be careful and go VERY straight, though, usually drill-press work).

If you need any help on tuning the engine, please shoot me a PM - I got four of the little things .....

Nice work on the build, please keep us updated.

[thgrahamjr]

Hey spyguy do you know any good sites to by parts for the 47cc pocket bike engines?

[SpyGuy]

Plenty:

www.davesmotors.com
www.scooterpartsdepot.com
www.scooterparts4less.com
www.partsforscooters.com
www.ebay.com

Dave's and SP4L.com are both really good on service and reliability - they ship out fastfastfast.

[lemegacool]

be sure to gear your setup for torque ... these little motors have a hard time pushing pocket bikes at start and i think your frame is heavier than a pocket bike frame, also your wheels are bigger than pocket bike ones (like 12"?) so be sure to put the largest sprocket you could find on the rear wheel, othewise the motor will overheat trying to pull you and it will blow up... i know i blowed the head on mine... now it's fully rebuilt with quality parts and it's stronger than before!

just my 2 cents other than that the frame looks badass

[thgrahamjr]

Thanks, I'm actually thinking of going with a jackshaft to gear the top speed down (for my son). It gives me more options, what do you all think?

[lemegacool]

jackshaft sound a good option!

[thgrahamjr]

I have a fake fuel tank that came off the bicycle that I'm going to modify into a working tank this weekend, I'll post pics of the process.

[thgrahamjr]

Here are some before and during pics of the fuel tank modifications, hopefully I'll have the welding and fabing done tomorrow.

[Raywelder]

Looks good :thumbsup:

[SpyGuy]

Run a jackshaft if possible. You may also want to consider running a CVT transmission for the bike, as well - I know several of the larger pocketbikes like the X series run them. Ditto on the big gear for the wheel, otherwise you'll never get it rolling ......

[thgrahamjr]

I was planning on going 6t on engine to 20t on jackshaft then 12t on jackshaft to 60t on rear wheel.

[cyborg]

cool

[SpyGuy]

Hey, so what's the score on the mini chopper build so far? Haven't seen anything posted lately. How did that pb engine work out?

[thgrahamjr]

Funds have put it on hold....lol