Many problems with chain drive system...

[ilandz]

I'm very new to motorized biking, having just finished turning an old 90's mountain bike into a speed demon. (or at least I hope it will be) The kit I got was a pretty standard 49cc 4 stroke from ebay.

The biggest problem I've had so far is the chain that connects the belt drive to the sprocket on the back wheel. The damn chain keeps jumping off the sprocket at high speeds, and sometimes when slowing down. I'm using the included chain tensioner, making sure the chain is tight but not to tight. The sprocket on the back wheel is on pretty good in my opinion with minimal wobble. The only solution I can think of at this point is maybe getting a spring assisted tensioner, but that about it. I can't say how many times I've had to take the entire back wheel off on the side of the road just to remount the chain.

One smaller problem I've had is the throttle getting stuck at full which is pretty annoying and dangerous. Don't know why it's happening, there's no sharp turn or bends in the line.

Any advice is desperately needed. thanks!

 

[Greg58]

Welcome to the forum, the first thing that comes to mind is sprocket alignment, make sure the chain is straight. On the throttle spray silicone in the twist area or lube the cable inside the housing. Maybe a small return spring at the carb if it had a external cable mount.

 

[Smooth Ave]

Hi, I have had similar chain issues with the 66cc China girl. I got rid of the tensioner, I tried the spring loaded tensioner, the issue there was in bump starts. I solved the problem with pex rigid water pipe. It is tougher than pvc or abs pipe. It is available in 5 ft lenghts at Lowe's, it is inexpensive. You would need to devised your own method to attach it to the engine end. I used tie wraps to attach it to the stays. It is easily cut with a hacksaw and file. You can form it with a heat gun or toaster oven. It is how I got the name "Smooth". We put one on my friend Bills bike and all he could say was smooth. Use half links to get proper chain length. Hope this helps. Riding WOT or I will stay home and knit socks.

 

[ilandz]

Thanks for all the help, I'll definitely be trying some different solutions. I think what I'm going to do at this point is get a better sproket and adapter, then try the pex pipe idea. And if all else fails I guess a jackshaft would work. I plan to try and stay active on this forum, thanks again for the help.

 

[Smooth Ave]

This is all about fun and finding what works. If you are using the rag joint then you might try just using one of the rubber donuts. Put the sprocket up against the spokes and use the rest of the rag joint. This makes it much easier to get the sprocket running true. Saves some money, hopefully solves a problem. Once you get it working you might go back and make a thin plastic spacer to go between the spokes and the sprocket. Good luck to ya neighbor.