Dec 11, 2019 · On my 08 YZ125 the pins fell out twice. I replaced the solid pin with a roll pins and they stayed in. I would be a lot more concerned about the missing or loose pin on the top right than the tips of the valve. Once those steel pins start moving in the aluminum valve body they need to be replaced!

Mar 11, 2013 · A few years ago I got a spare '06 YZ125 engine from a friend which had a broken case. I had a 2008 model at the time so I figured it was good for spare parts. From the looks of the damaged engine, it assumed it was from someone running the chain too tight.

May 25, 2014 · Full motor rebuild was done about 7 hours ago. Questions- has anyone else had one of these break or heard of it happening? Would your guestimication be that piston-to-valve contact occurred first causing it to break? Is that even possible? Or that the power valve broke and then contacted the piston? Thanks! "Gunga galunga. Gunga gunga da gunga."

Feb 28, 2023 · Stripped down top end, 1 wrist pin clip is missing and piston has broken at clip location. 3 gouges to cylinder, bottom end is locked and I suspect the wrist pin clip has jammed there, bottom end not yet disassembled.

Jun 9, 2017 · I've heard someone that works in engine development at a major auto manufacturer say that with modern plated cylinders, coated pistons and alloy piston rings, engines are 95% broken in in the first minutes of running.

Oct 20, 2012 · Get it up to temp and test with the stock jets. Drop to the next size down and repeat. Listen/feel for any signs of too lean. If none, drop to the 2nd size down. My guess is you will notice an improvment. If not, time to look for other issues besides jetting.

Oct 9, 2021 · I had this happen on my first yz125, replaced it, and it turned out the motor was pretty badly clapped out. I would bet your bottom end needs a rebuild and everything. Worth mentioning.

Oct 19, 2010 · Rode for 10 minutes, stopped to talk and when I went to start back up, my 2nd kick I hear a "clunk" and something hits the ground. I look to see my kickstart lever and thinking "oh I probably just broke the bolt or didn't tighten it enough when putting it back on." SIKE.

Apr 18, 2023 · Take off the right-side Case-Cover (Super easy, just be careful when torquing down the bolts after putting the cover back on, as those fucking bolts are very easy to break. And trying to get a broken bolt out of your engine case is NOT a stress free task, lololol).

Jun 22, 2024 · sign the engine ran excessively hot. (lean jetting, fuel delivery issue, air leak etc.) Explain in detail how you were riding the bike when it seized, my guess is that you were 'road' riding at sustained wide-open throttle.