cr125 top end issues

jtadymx
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jtadymx
Edited Date/Time 8/13/2014 7:50am
hi, I have a 2004 cr125 that I just bought. I rode it maybe 2.5 hours on what was supposedly a new top end and suddenly lost all power. crank is not seized and upon disassembly the issue was obviously the gnarly nick and scratch out of the side of the piston. also the when cold started the bike revs unusually high. could this have contributed to this?
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rmartin517
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rmartin517 8/13/2014 3:11am
8/13/2014 3:11am
Sounds like it may have had an air leak. Check the cylinder make shere the plating is good and just put a new top end in it. Any time I buy a used bike especially a 125 thats one of the firsth things I do. Drain the gas becasue no telling what there, clean the carb and put a new top end. Everyone lies about what is really going on in the motor.
EL Sammo
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EL Sammo 8/13/2014 6:51am
8/13/2014 6:51am
Have a very close look at your big end and main bearings, even if the movement and amount of play feels ok the bearing cages can fail and send bearing cage parts on a very bad trip around the engine.

The crankshaft seals can also be damaged by this and cause an air leak which can cause a high idle.
Mr Bean
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Mr Bean 8/13/2014 7:50am
8/13/2014 7:50am
More specifically, the stator side seal can leak air and cause high/erratic idle and a seizure.

You can test when running by removing the stator cover and spraying a shot of starting fluid (ether) at the seal area and see if the engine revs up.

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