Chain does not fit sprocket - please help

A

atomicmiata

New Member
Hi,
my first post here.
I just bought an engine kit off ebay from boygofast.
an 80cc kit. (I know it is probably -70cc)
the chain pitch does not jive with the rear sprocket pitch.
(it appears that the chain would need to stretch considerably to fit)
anyone seen this before?
should I buy a new chain? what size?
or buy a new sprocket? if so, from where?

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thanks!
steve in frederick, md
 
boy go fast huh? Hmmmmm, seems to be a pattern here. Have you contacted him about a chain and or sprocket replacement?
 
just wondering the chain appears to be seating on the bottom side of sprocket do you have the sprocket parallel with the tire or perfectly centered on rear rim. that was the problem with mine when i first put together
 
I took the sprocket to a motorcycle shop today to try a different chain on it.
a 420 sized chain fit the pitch of the sprocket perfectly, tho a 420 is quite a bit wider which is not good.
anyone know of another size chain that has the pitch of a 420 but is narrow in width?

thanks!
-steve in frederick, md
 
Ok the coating on the sprocket is too thick. Dax says use a grinder to gently "buff" the plating off of it. I am never one to follow and took mine outside and found a rough piece of sidewalk. Scraped it till it looked good. Not much! just a little. Both sides.
 
atomicmiata said:
I took the sprocket to a motorcycle shop today to try a different chain on it.
a 420 sized chain fit the pitch of the sprocket perfectly, tho a 420 is quite a bit wider which is not good.
anyone know of another size chain that has the pitch of a 420 but is narrow in width?

thanks!
-steve in frederick, md
Click to expand...


#41 chain from the Tractor Supply Co. or other places is a perfect fit to the standard China In-Frame kits.
 
Great looking red bike.

I learned the hard way with the tensioner back by the sproket the motor will twist the tensioner loose and into the spokes. Consider taking one link of chain out and moving the tensioner farther away from the sprocket.

Good Luck with you build
 
The kit I got from BGF had a scrap sprocket. Same deal as you describe. Poor tooth form, and deep gouges in the face near some of the teeth. I would almost be willing to bet that these sprockets were in the scrap barrel at the Chinese factory and someone pulled them back out. I pitched it in my U.S.A. scrap barrel and made another one for my last build.

As the other guys pointed out you may be able to fix it...

Our kit from Chris @ bike-to-moped came with a chrome sprocket that fit perfectly. I've ben told that the chrome sprockets have a more true tooth form. Apparently they take a little more care in manufacturing for the ones they chrome.

Jim
 
HI,

Grinding the sides of the sprocket teeth and tapering them slight inwards towards the tip should take care of that problem.....

I used to encounter the same thing until I started making sprockets.

Hope this helps.

Andrew

FWIW - I think the problem is a bit more universal than with one particular manufacturer because I have bought from a few different vendors and sometimes it was hit or miss on the sprocket thing but grinding always took care of it....BUT I never knocked the tips down tho...
 
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