Coolster 125 (110) wont run. - ATVConnection.com ATV Enthusiast Community

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Coolster 125 (110) wont run.

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  #1  
Old 10-10-2018, 05:27 PM
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Default Coolster 125 (110) wont run.

Coolster 3125r with a mislabeled 110cc engine. Newer top end rebuild.

ran great, then just stopped and wouldn't restart.

Timing was off by 1 tooth, so I adjusted that. Adjusted both valves to .005. Getting 125 psi compression. Good spark, but put in a new plug anyways.

Still won't run. It will so mn etimes fire and limp along for a few seconds, then backfire out the carb and quit.

Thought it might be a carb issue, so I slapped a new carb on it (even though the old one was only 6 months old).

still runs the same.

I'm out of ideas.

what's next?
 
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  #2  
Old 10-11-2018, 02:22 AM
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It is just possible it wasn't the valve timing out, but the T mark. If the flywheel moves round on the crankshaft, it puts the ignition timing and T mark out. Check that TDC of the piston and T mark agree. Still most likely to be carb though, clean the old one out and put it back on.
 
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  #3  
Old 10-11-2018, 03:35 AM
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I'll check it out. Thanks.
 
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  #4  
Old 10-11-2018, 04:25 PM
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Did the straw trick, the "T" is TDC, or close enough I cant tell it's off. Pulled the cover anyways, it's on tight. Don't have the right puller to get it off, but I can see the key in the slot on the flywheel, and it looks OK. Cant see the slot in the crank, though. Bummed- I was convinced that was the problem.

had a new CDI lying around, no change.

as far as carb- what are the odds of a new carb being messed up in the same way as the old one? I even tried putting a little gas in the plug hole, with no luck.
 
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  #5  
Old 10-12-2018, 02:07 AM
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"what are the odds of a new carb being messed up in the same way as the old one?" Quite high, can't hurt to clean out the old carb and re-fit it.
 
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  #6  
Old 10-13-2018, 04:19 PM
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Just an update- cleaned the old carb, even had another one lying around. Still nothing. Pulled the flywheel, looks fine.

here is where I make myself look stupid- decided to check the spark again to see if it seemed to spark at roughly the right time.

it sparks, barely, for a few revolutions, then just kinda peters out. Obviously, it's an ignition problem. Parts are cheap, so I ordered an upgraded cdi, coil, and stator for it.

I feel stupid, my initial thought was spark, so I pulled the plug, held it to the head, and hit the starter. Saw a spark, and immediately crossed it off the list.
 
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