Trevf98 Posted June 2, 2014 Report Share Posted June 2, 2014 (edited) I know this is off topic but I would appreciate any help. On Saturday I bought a 2006 yz 125 with a 134 kit in it with 5 hours on the top end and crank. I rode it that day later on and it was fine. Then on Sunday I rode it again for a while then I took a break. I went out again and it shut off after about 30 mins of riding. I pulled the plug out and the tip was white and the spark plug tip was bent into the electrode. I put a new plug in and it wouldn't start. My friend towed me a little ways and It finally started after he dragged me. I drove it home but on the way home it would barely hit power band if it did at all. It won't start unless it's jumped started. I'm pretty sure it blew up but I'd like to know what failed. The bike is running lean I'm sure. If it helps I mixed 32:1 with maxima super m with 93 octane gas. Edited June 2, 2014 by Trevf98 Quote Link to comment Share on other sites More sharing options...
Trevf98 Posted June 2, 2014 Author Report Share Posted June 2, 2014 And yes the bike will run but not good and I'm not risking running it when it could be blown Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 2, 2014 Report Share Posted June 2, 2014 do a leak-down before you tear it apart. pull pipe and look at piston/cyl through exhaust Quote Link to comment Share on other sites More sharing options...
Trevf98 Posted June 2, 2014 Author Report Share Posted June 2, 2014 do a leak-down before you tear it apart. pull pipe and look at piston/cyl through exhaust Do you think the piston hit my spark plug if the top of the plug was smashed into the electrode Quote Link to comment Share on other sites More sharing options...
alexardoin Posted June 2, 2014 Report Share Posted June 2, 2014 You're running the bike really lean. That's why the tip of the spark plug is white. The electrode didn't touch the piston. The gap on the plug has closed up from detonation. The detonation is caused from running really lean. Like mentioned, do a leak down test. If you're lucky, you'll find an air leak but not have damaged the motor. Most likely, you've started to damage the piston and now have no compression. Leak down test first to check for leaks. If it passes the test then check your carb to make sure it's clean and properly jetted. Report your findings here. Quote Link to comment Share on other sites More sharing options...
BUILDER Posted June 3, 2014 Report Share Posted June 3, 2014 You hurt the motor. Do all the leak down tests you want but that sucker is blown! Quote Link to comment Share on other sites More sharing options...
Trevf98 Posted June 3, 2014 Author Report Share Posted June 3, 2014 Yeah I opened it up it needs a new piston. The good news is the crank is good Quote Link to comment Share on other sites More sharing options...
wayne_smith97 Posted June 3, 2014 Report Share Posted June 3, 2014 Did you do a leak down test before you opened it up? Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted June 3, 2014 Report Share Posted June 3, 2014 Did you do a leak down test before you opened it up?ADVISE IS USELESS!!! Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 3, 2014 Report Share Posted June 3, 2014 (edited) A leakdown test before dissasembly might point to something that needs to be fixed while down for rebuild. Standard examination procedures such as looking in ex and intake should be a given. pv engines can be a MOFO on leak testing. JMHE Edited June 3, 2014 by Larry's Shee Quote Link to comment Share on other sites More sharing options...
Trevf98 Posted June 3, 2014 Author Report Share Posted June 3, 2014 Piston cracked Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted June 4, 2014 Report Share Posted June 4, 2014 No chunks in bottom end? Quote Link to comment Share on other sites More sharing options...
Trevf98 Posted June 4, 2014 Author Report Share Posted June 4, 2014 No chunks in bottom end? No the chunk shot out of the exhaust I got so lucky. I have zero scratches on my cylinder. Everything is in perfect shape I order a new top end and it's good to go. I feel like I won the lottery. Quote Link to comment Share on other sites More sharing options...
sprinklerman Posted June 4, 2014 Report Share Posted June 4, 2014 Piston crackedThe question is WHY the piston cracked... Sent from a van down by the river Quote Link to comment Share on other sites More sharing options...
camatv Posted June 4, 2014 Report Share Posted June 4, 2014 FAIL Quote Link to comment Share on other sites More sharing options...
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