Sprocket Help - Chinese Gokart Predator Swap

10Terp

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Hi guys,

I recently bought a Dongfeng 125cc go kart for next to nothing. It came with a 125cc honda clone (RN123) and it just didn't have the guts. I'm working on a Predator 212 swap and have the engine mounting system more or less finished. I'm running into some sprocket issues.

The chain and sprockets for the stock 125cc engine are all 428 (pretty common in the motorcycle world). The challenge is the 30 series torque converter I put on the Predator has a #41 sprocket which may or may not work with a 428 chain (it meshes decently well but not where I want it to be).

I'm looking to find a #41/420 sprocket for the rear axle of my kart and do this all the right way, but having a hell of a time finding something that will work. Here's the sprocket that came off:

1603905202408.png

It mounts to this hub on the axle:

1603905326070.png

Does anybody have any input on how I could solve this? I tried to find a 428 jackshaft sprocket for the torque converter, but I don't think they exist. Right now I'm thinking my best option is to buy a blank 420 sprocket and drill the holes myself, but even then finding one with the right bore hold diameter is challenging.

Thanks!!
 

Karttekk

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Could you possibly weld something like this to your existing sprocket then move your engine over to make up for the added thickness?
 

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jamyers

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I feel your pain - finding sprockets that fit chains and axles can be a real pita.

If I understand, you're looking for a Size 41 sprocket, with 50 Teeth, that'll either bolt up or can be drilled to fit on a 36mm axle?

For reference, here's a chart I found showing the differences between sizes:
 

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10Terp

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I feel your pain - finding sprockets that fit chains and axles can be a real pita.

If I understand, you're looking for a Size 41 sprocket, with 50 Teeth, that'll either bolt up or can be drilled to fit on a 36mm axle?

For reference, here's a chart I found showing the differences between sizes:
That is correct. Thanks for the links! I'll check them out.

Just did some Amazon searching and found this:


Wound up ordering it. I'll have to figure out how to bore out the center hole to 36mm and drill mounting holes, but it should work ok.
 

madprofessor

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Why all this complicated fuss and such? If your CVT (torque converter) didn't come with both a #41 and a #35 drive sprocket, just order a 12T-#35 sprocket in your CVT's shaft size from the dozens of suppliers on Ebay. Use a #35 chain to the axle and you'll never be short of available options for ratio change later if desired. I recommend using a sprocket hub on the axle with a 2-piece split sprocket of your choice. Then you can change the number of teeth with just the 6 screws that hole the split sprocket to the hub. Never be forced to slide bearings and sprockets and brake discs off the axle again.
 
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