Chain snapped on my gas bike why?

[MrBones420]

Hi so I was riding home from work on my bike and my chain snapped on me. well I peddled home and took look and one of the pins that holds the links together came out so I took the clutch cover off and to the left of the sprocket the chain was rubbing agenst the cover (photo of the ware) almost as if the chain was to tall for the engine but it's the stock chain. I'm confused and frustrated cuz it's how I get to work. if anyone can help me figure this out I would surly appreciate it.

 

[Tyler6357]

Get a dremel tool or file and cut out some of the medal until the chain doesn't rub. Another option is to use a strong BMX chain. I have a Wippermann Connex 1R8 and I found that it gives me more room for the chain to clear the tire and it runs through the engine sprocket with less drag than the bulky 415.

 

[FurryOnTheInside]

The kit chain is junk.
The engine sprocket is poorly designed, compare it to any bicycle sprocket and you'll see the teeth have a different shape. It is also poorly made, often having burrs on it's edges. Both these things can cause damage to the chain and/or prevent the chain seating fully onto the sprocket.

I use 1/8" bmx chain too (KMC Z510), although I decided to grind the engine sprocket to make it narrower (0.12") while I was reshaping the teeth.
I can't see any point in replacing the kit chain with another #415 (3/16") chain because it doesn't need such a thick heavy chain. My next chain will be 3/32"!

With a better tooth profile the chain can fully seat on the sprocket.. that was probably one of the problems, but you might also have had too much slack. You might also consider packing the excess space around the sprocket with some epoxy resin.

Anti-skip chain thing again

• FurryOnTheInside
• Sep 19, 2017

I should've greased the box to allow it to release but was worried I would touch the case and...

 

[Tyler6357]

That epoxy resin is a brilliant idea! I ran my bike for 2000 miles and then the chain kept getting jammed. I took a few links out of my chain but that didn't solve the problem. I finally replaced my engine sprocket, the teeth were totally worn down and it hasn't gotten jammed since then but I think I will try some of that epoxy just to make sure it don't happen again.

 

[MrBones420]

Ok cool thank you guys but one question if I get the 1/8 chain will I have to modify the sprocket

 

[FurryOnTheInside]

Ok cool thank you guys but one question if I get the 1/8 chain will I have to modify the sprocket

I would/did make it narrower, 0.12" to perfectly fit the 0.125" chain. So IMHO yes you will have to.
I would/did correct the tooth shape too, they are too square topped, should be more rounded so the teeth slip behind the rollers without catching and lifting the chain. IMHO this is 100% necessary too.

 

[Will'smotobikes19]

Hmm interesting never heard of people using bmx chain on their 2 strokes I guess it would cut down on weight of the chain and perhaps make the bike go a little faster. the 4 stroke 79 has more torque and ccs than the 2 strokes so I wouldn't count on bmx chain personally. I recommend using #415 Regina chain its Italian not Chinese its for the motocross bikes, I think it has less play than the China chains and its tougher. The smaller chain reminds me of some people that use chainsaw engines that weld a sprocket on the clutch.

 

[Spare_Parts]

You can buy a narrow 10 tooth sprocket from bicycle motor works. Fits the 410 and kmc 510 chains.

 

[MrBones420]

Get a dremel tool or file and cut out some of the medal until the chain doesn't rub. Another option is to use a strong BMX chain. I have a Wippermann Connex 1R8 and I found that it gives me more room for the chain to clear the tire and it runs through the engine sprocket with less drag than the bulky 415.

Did you have to modify the teeth for that BMX chain to work I gotta get to work today so having to grind the teeth will take to long

 

[Will'smotobikes19]

I'm sure the chain he's talking about is the right size for that smaller sprocket since he said 410 kmc meaning the teeth would be fine it should just be smaller width. If I do another 2 stroke build I might have to try a smaller sprocket and chain does it wear faster than regular chain? any power improvements?