I have a 21' Yz125 and I've got 60 hours on it. Did the first top end at 30 hours, everything looked good and put it back together. 15 hours later I had a bad coolant leak down the front of the motor just below the exhaust port. I chalked it up to a bad base gasket so when I tore everything down I noticed the cylinder nuts were all loose and barely finger tight. So I replaced the gasket and installed a new ring while I was in there and re torqued everything and put it back together. I have now gotten to the time to replace the top end again and upon tearing down I found the cylinder nuts loose again (not loose enough to leak coolant but for sure not to the torque spec). Is this a common issue with the Yz's? Or is there something I'm doing wrong? I may put a little loctite on the nuts to hopefully avoid this issue again.
1) Are you sure you're torqueing them evenly and 2) Have you verified that the studs themselves aren't backing out? Good luck
Yes torqueing them in a criss cross pattern to the spec in the manual. And it did not appear that the studs are backing out
Internet rule #1. Don't ever post your nuts are loose.
Not sure what size the nuts are but look into replacing them with a mechanical lock nut, the type that has a crushed thread to help keep them tight. Or serrated flange nuts which bite into the cylinder to also help keep from backing off
The Shop
Free shipping: VITALMX
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Do yourself a favor and double check that those studs are tight. I'm betting that is your issue. I had a couple come loose on one of my YZs years ago.
I did a handful of top ends on an 09 yz 125, after 2 hours i would take the pipe back off and retorque all the base nuts. I could get atleast a 1/4 turn on each of them. If you aren't already, use a metal base gasket. I like the tusk ones, because they are cheap and have never failed me, and you don't have to scrape them off every top end.
Did you use new copper crush washers?
This isn't on the head that I'm talking about. This is on the cylinder I don't think they had crush washers on those
Are you torqueing them to spec or doing it by feel? I do it by feel and have never had 1 come loose. But I've seen ones torqued to spec come loose. I'd take it apart and check the studs as others have suggested.
Check to see if the studs are stretching. Replace studs.
Post a reply to: YZ125 Cylinder nuts keep coming loose