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How do I fix locked up motor

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Robert T Spurlock

New Member
Oct 30, 2019
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Akron Ohio
Hi I received my new 80cc china girl about 3 weeks ago and been finding flaws in the kit set up the chain master link catching the cheap plastic roller on the tensioner and popping off, a spring loaded tensioner with a metal gear should be the fix and I eliminated the master link looking for a tensioner and gear. But now my problem is while riding the bike started vibrating bad the the motor shut off instantly and a link in the chain snapped. I fixed the chain and get the bike going but still vibrating and stalled and did that a few times then the motor locked up let of the clutch and the back tire skids. Now I took out the spark plug and tried turning crank with ratchet and the motor wouldnt budge forward so I tried to turn it backwards and it moved and it blew my brothers thumb off of spark plug hole big time. Can a clogged muffler baffle cause that super compression and lock the motor?
 
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Greg58

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May 1, 2011
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Sounds like a piston or ring broke, I would pull the head and lower the piston to the bottom and look for scratches or plating missing from the cylinder wall. You can reuse the head gasket, just torque the nuts to 12 foot pounds when you put the head back on.
 

Greg58

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May 1, 2011
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If your chain is catching on the tensioner wheel you need to bend or twist the tensioner arm so the wheel runs parallel with sprocket. I've had to tweak everyone I've used.
 
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Robert T Spurlock

New Member
Oct 30, 2019
15
4
3
46
Akron Ohio
If your chain is catching on the tensioner wheel you need to bend or twist the tensioner arm so the wheel runs parallel with sprocket. I've had to tweak everyone I've used.
I tried that and things worked fine after eliminated the master link until it all the sudden shut off while in full throttle and a chain link busted which also ruined the idler and roller. I'm waiting on a new spring loaded tensioner with a sprocket and new cdi to arrive.
 

Robert T Spurlock

New Member
Oct 30, 2019
15
4
3
46
Akron Ohio
Did you find what locked up the engine?
No but when I got it unstuck and started it it had tremendous power and pulled the chain off the back sprocket but it kept running till I shut it off. I bought a thunder cdi in hope that it may be the problem, but I'm gonna take the acorn nuts off the head and replace and tighten cause I noticed some oil dowat the bottom of the case. I will look at the piston and rings also , just waiting till the parts are delivered cause the bike is at my brothers muffler shop.
 

indian22

Well-Known Member
Dec 31, 2014
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Oklahoma
Chain didn't come off due to tremendous power but ratherpoor installation and alignment of chain line. Engine, wheel/sprocket cocked at an angle or tensioner lateral adjustment off....perhaps chain tension too tight or too loose. one some are all of these will throw or even break a chain. These are just some of the reasons a chain can come off the sprockets, but bottom line is you've got to figure this out!

Rick C.
 
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