New sd stinger motor ran briefly now won’t start..

Misfitchopper1990

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Jun 19, 2019
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So I just got a new stinger 80cc kit and decided to upgrade from the previous motor I had on my mini chopper. I got it all together, took a few tries to get it running but it was finally going. Then my chain popped off the rear sprocket, and the engine cut out. I figured I just needed to put the chain back on and it would be fine, but I was wrong. Also, the clutch was sticking so I re adjusted it and the bike moves and acts like it wants to start but no chance.. should I try replacing the Cdi? the motor gets fuel and the spark plug works but it’s a low spark.
 


CrazyDan

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Jul 9, 2016
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2,752
You may have broke a key on one of your shafts, bringing the timing out. A major change in how an engine acts is usually from a major change, wanted or not.
Edit: you seem to be missing a part of your master link from the pic. Right where the chain run passes your left seat stay I see a plate only on one side.
 

Misfitchopper1990

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Jun 19, 2019
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You may have broke a key on one of your shafts, bringing the timing out. A major change in how an engine acts is usually from a major change, wanted or not.
Edit: you seem to be missing a part of your master link from the pic. Right where the chain run passes your left seat stay I see a plate only on one side.
Is it typical to break a key on a shaft for a brand new motor? Today is the first time it’s ever ran
 

GreasyChris

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Jan 3, 2019
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Is it typical to break a key on a shaft for a brand new motor? Today is the first time it’s ever ran
These are Chinese made parts with sketchy quality control at best, so anything is possible.
Id start with a compression test and make sure all the parts that are supposed to turn,turn, and check for spark using a spark tester. Spark on the outside of the cylinder means nothing, it needs to be able to spark in the jug while under compression. If you don't have a spark tester, you can get one aft harbor freight for cheap or replace cdi with a known good one. Being a new kit maybe the carb is jetted wrong. These are a pretty simple engine it shouldn't take you long to get it figured out.
 

Misfitchopper1990

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Jun 19, 2019
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Well I took the magneto cover off of the brand new engine... found that the magneto sheared off the threaded end of the crankshaft... fml🤦🏼‍♂️ On the upside I have a spare motor, would it be a good idea to tear em both down and replace the crank shaft with what I have, or order a new crankshaft?
 

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