Sprocket drama

C

CorollaWil

New Member
New here, need help. Sorry if i made a thread that already exist, but i cant find anything related to this issue. So i just bought a walmart huffy cranbrook recently and wanted to throw a motor on it. Everything went on smooth except that damn sprocket. The problem with it is the sprocket opening is too small to fit on the wheel hub. Its got coaster brakes as if that helps. I tried to wing it, but obviously failed. The rubbers things that go between the sprocket and spoke are way too thick. I tried removing them to see how it works, now the sprocket fits snug on the hub, but the braking is crap, and it shakes from the hub spinning inside the sprocket opening. Now im at a brick wall. Is there a trick to this, is the cranbrook wheel not made for this? Do i need a different sprocket? Different wheel? Im a virgin to motorized bike building so any guidance would be appreciated. Thanks guys.
 
You have to grind out the center of the stock sprocket to fit over the hub. Then it should be smooth sailing once you get it completely aligned.
 
When I initially installed the rag joint, I had to put a couple of bends in the brake lever to clear the inside of the sprocket ---- worked great with no grinding required. Might check to make sure that the brake lever is rubbing the sprocket.

The best solution is to upgrade the rear wheel with Shimano internals and a sprocket and hub adapter from mzmiami.com. Well worth the money!

Best of luck in your search for your solution.
 
xseler he is saying the sprocket opening won't fit over the outside of the coaster hub, not that the brake arm is causing problems. I agree though on the hub adapter. Worth the upgrade. I spent a ton of money building a bike and never wanted to shell out the $50 for a hub adapter, but I finally did and it was worth every dollar.

Also yes the sprocket has to be as close as you can get it to perfect because otherwise depending on what part of the sprocket you are on your chain could be tight or loose. Which can result in a jumped chain or a broken chain. It's really a pain in the butt to get a rag joint proper.
 
I bent the brake lever to avoid it rubbing the heads of the screws so thats all good. Its just the sprocket not wanting to sit on the hub. I guess the hub is too short to fit the sprocket, rubber (rag joint?) And brake lever all together. If i remove the rubber, the sprocket sits om the hub and alligns perfectly, but like i said, the braking causes a shake from the hub which feels horrible. So if i grind out the center of the sprocket it, should i make it wide enough to fit over the hub dust cover? Or should i just eliminate the dust cover and grind the sprocket to fit the hub? (Thanks for the quick replies guys, sucks i have to go to work in the morning and spend my shift with motor fever now, cant wait to get this sprocket on!) Lol
 
CorollaWil said:
I bent the brake lever to avoid it rubbing the heads of the screws so thats all good. Its just the sprocket not wanting to sit on the hub. I guess the hub is too short to fit the sprocket, rubber (rag joint?) And brake lever all together. If i remove the rubber, the sprocket sits om the hub and alligns perfectly, but like i said, the braking causes a shake from the hub which feels horrible. So if i grind out the center of the sprocket it, should i make it wide enough to fit over the hub dust cover? Or should i just eliminate the dust cover and grind the sprocket to fit the hub? (Thanks for the quick replies guys, sucks i have to go to work in the morning and spend my shift with motor fever now, cant wait to get this sprocket on!) Lol
Click to expand...

Grind it out and keep the dust cover. I have my old 36T grinded out that I used on my bike and it worked like a charm. The rag joint is the rubber mounting system and is a PITA, but I wouldn't run it without both sides of the rubber. Just take a little time and grind out the center with a dremel or something and you'll be scooting along in no time.
 
The hole in the center of the sprocket doesn't need to be perfect. It can be oval, square or anything large enough to fit over the hub without interference.

The critical thing is the sprocket teeth being perfectly concentric to the hub. With the sprocket installed (use the rubber parts, please) you should be able to spin the wheel and not see any wobble in the sprocket. It should run as true as the rim. No off-center or lateral wobble.

This takes some work but the kit supplied 'rag joint' sprocket attachment parts will work well if installed correctly. By correctly, we mean aligned with the engine drive sprocket and no wobbles. It MUST be centered on the rear hub so it is concentric with it.

Aftermarket sprocket adapters are nice...but not essential.

Tom
 
The stock sprocket will eventually rip the spokes out of your wheel. Do yourself a favor and spend the extra $50 on a hub or disc-brake mounting sprocket. You won't regret it.
 
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