Chain Problem

Phil1958

Phil1958

#1
#1
my bonanza with a jack shaft has broken two
chains so far. what i have is a front peg with a
swing arm. the engine is a 212cc predator with
a 12 tooth clutch with 41 chain driving a 12 tooth
gear on the jack shaft. on the left side of the jack shaft
is a 17 tooth gear driving a 45 tooth gear with a 41
chain. i used a square to line up both chains and lube
the chains on a regular basis and had no problems on short
rides.

on longer rides the chain between the jack shaft and
sprocket breaks after about a mile of road riding every
time. both chains were new from OldMiniBikes. the picture below
shows one end of the chain, the inner plates expand and
some of the pins look like the outer plates are moving outwards.



is it a chain tensioning issue or alignment or what?

what to do???????

phil
 
ogygopsis

ogygopsis

#5
#5
Phil, I just can't imagine even a bad batch of chain breaking under the riding conditions you described. When you lined your sprockets up did you lay a good straight edge across the rear sprocket and move the forward sprocket so that the "faces" are parallel? The ruler should lay flush against the faces of both sprockets. Secondly, did you check your setup to see if your rear sprocket may be off center or out of round. An off center rear sprocket will cause the chain to run loose at one point and then very tight at another point. Prop your bike up so the rear wheel is off of the ground. With the chain installed; rotate the rear wheel slowly and keep checking the chain to see if it loosens and tightens then loosens then tightens. There's something causing undue stress on your chain and causing it to break. On a minibike setup there are only two primary types of stress put on a chain. The first is tensile (pulling or stretching) caused by out of round sprockets and the second is torsional (twisting or sideways flexing) caused by the sprocket faces not being parallel and flush with each other. If your sprockets are properly aligned and centered you should be able to run non-stop for hundreds of hours without any chain problems; especially with a #41 chain. Let me know what you find out. Ogy
 
oscart

oscart

New Member
#6
#6
Are the sprocket aligned properly? I have seen pics of minibikes on this page where they are not even close. Also, make sure that the chain is not adjusted too tight as well.
 
oscart

oscart

New Member
#7
#7
Not familiar with that chain but the price is very cheap. I bought Xtreme #35 chain in a 10ft length and paid about $75.00. If everything else checks out, then you need to purchase a quality chain. Not saying you have to spend $75.00 but...
 
oscart

oscart

New Member
#8
#8
Last point, there doesn't seem to be any oil on the chain in the pic unless you just cleaned it. Without proper lubrication, the pins will heat up and could cause breakage.
 
Phil1958

Phil1958

#9
#9
i did clean the chain in my parts cleaner after it broke
so it would look pretty for the picture.

you bring up a good point about the rear sprocket being
off center. i used a framing square to line up the sprockets
at one point in the position of the rear wheel.

i've seen threads here that address off center and wobbly
sprockets, wheels, and the like.

it's time to put the bike up on a stand and look for these
issues.

thanks for the help all :thumbsup:
 
1

1sinner

New Member
#12
#12
useng1 said:
Make certain you aren't running a #40 sprocket instead of the narrower #41. Pitch is the same.
Click to expand...
That's what I am thinking too. Make sure the sprockets aren't too thick for your chain.
I didn't pay attention when I changed a sprocket and realized when I started it up something was wrong. I then noticed that sprocket was thicker. I used my belt sander to thin it out some (being careful not too heat it up too much.). I'm thinking that the way you are describing the spreading of the plates, that you probably do have the wrong chain/sprocket match.
 
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