I ride a 1999 Honda cr 125. My bike wouldnt start anymore after a few minutes of riding it one day. So I took the top end apart and a small piece of the piston had chipped of from the top, above the ring. It scratched up my cylynder and jacked up the piston. I figured it might have just been some debris that got inside and jacked it up. I got it resleeved and put a new top end in it. After a few minutes of riding it it felt as if it had lost all compression and it wouldnt turn on. I took it apart and it had done the same thing. A piece chipped off from the top and there were wear mark on the sides of the piston. Please help me out.
Chipped Top End!! Please, please help!!
- Thread starter chavez27
- Start date
va_yzrider
Member
- Apr 28, 2003
- 353
- 0
Check your carb slide. This happened to my brother's KX and caused serious problems. Also, check your reeds to see if they came apart. Both of these guesses assume that it is something getting into your cylinder, not the piston coming apart. Worth a shot.
- Jun 5, 2001
- 7,529
- 18
It sounds like it's catching on something like the exhaust port. When you redid the top end, you changed rings and all, right? Your exhaust valve may be slipping deeper into the cyclinder head so check that as well. That's usually the only moving part that comes near it. If you have too much play in the piston it'll move around in the port as well. You should be able to see what side chipped off, then go from there. Look at your port openings and make sure there's nothing stuck in there. If you had it resleeved it should be back to specs but I believe you can't run both types of pistons anymore. FWIW, in the future, you can have your cyclinder worked back up and replated, that way it stays stock instead of the sleeving. It may cost a bit more, not by much but you can then run both types of pistons.
- Thread starter
- #5
And it was a piece of the piston that had broken off. I know that beacause when I took it apart I found the small piece off piston imbeded into the top of the piston. It had came off from the front, top left side of the piston, right above the ring.
- Jun 5, 2001
- 7,529
- 18
It could either be that when you put your rings on they may have been opened and bent a little too much and it caught on the exhaust port or the exhaust valve is coming to far into the cyclinder. If it is on the top then it is happening when the piston is coming down and maybe the ring is catching on a port which causes the top of the piston to break off. Did your ring break as well?
The vertical lines are from blow by most likely unless they are gauges, then in that case the rings are screwing up.
The vertical lines are from blow by most likely unless they are gauges, then in that case the rings are screwing up.
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Been There. Send off your cylinder to Eric Gorr http://ericgorr.com/ so he can straighten out your cylinder. Sound like they missed when they installed your sleeve. Also send your head with it. :ugg:chavez27 said:
firecracker22
Sponsoring Member
- Oct 23, 2000
- 3,213
- 0
What does it mean if this same thing happens on a really old, no power valve, no reed valve, air cooled DT 400? I'm afraid to put the new piston in it now--what if it happens again? I have not the time, money NOR inclination to send the cylinder of a $500 motorcycle off to EG.
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