piston only works in reverse

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stuffandstuff

New Member
Oct 11, 2010
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Asheville
put a 66cc engine on my vike today, the only thing I did they may have cause this is when I threaded my chain through the motor sprocket and felt some resistant then it gave all the sudden. now whne engagin the cluching trying to start it, it has no compression in fact the piston does not moved, I discovered that the piston will move when I move the bike backwards... any ideas? did I pop something loose in the clutch gear?

Thanks guys
 
Al.Fisherman

Al.Fisherman

New Member
Sep 9, 2009
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Calera, Alabama
Turn the engine around....:>)

No if the piston moves up and down while you roll the bike backward..It should move while pushing it forward.
1. Remove the chain
2. Use a socket and rotate the crankshaft (both directions), Use the shaft that the magneto is attached to..see what happens.
 
Last edited:
2door

2door

Moderator
Staff member
Sep 15, 2008
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Littleton, Colorado
I'd say turn the bike around and ride in reverse. You'll need good mirrors though. :)

Now, seriously, check your chain tension and alignment. It sounds like the chain is bunching up on the drive sprocket. Chain alignment and tension are two of the most important things about an engine installation.
Tom
 
GearNut

GearNut

Active Member
Aug 19, 2009
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San Diego, Kaliforgnia
Also, just judging by your statement of "felt some resistant then it gave all the sudden",
check the engine's sprocket nut well as the clutch center nut and crank shaft pinion gear nut to be sure that they are tight. If you find one loose, do not tighten it but remove the item that the nut holds on, be it sprocket, gear or whatever. Inspect the woodruff key and keyway in the shaft and gear, ect. If a woodruff key slipped or sheared they can sometimes act like a one way clutch. The rotation will grab one way and slip the other way.
Also if the factory failed to install a key, just the keyway can act like a weak strength clutch as well. Any burr on one side of it can catch in one direction and slip in the other direction.
 
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stuffandstuff

New Member
Oct 11, 2010
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Asheville
Thanks for the replies, got it working. it was the crankshaft, I just turning it to the right, and to the left and voila... it works now. never had that happen. I thought it was going to be the clutch in which I always find difficult to mess with.
thanks again!
 
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