I went to went to run my YS 140 over the weekend and found there was no compression. It hadn't been run in over a year but had been stored with Ultra Oil from Performance Specialties. We got it running but not with good power and way too much smoke no matter where the needle was. I figured it was valves or rings so I removed the head and everything was fine there...must be a stuck ring. Any suggestions on how to loosen up that ring without doing a complete teardown? I've tried a little oil down the cylinder to try and loosen the ring but with no success. Any advice would be appreciated.

Thanks,
paul

Are you sure it's not a stuck valve? Have a friend that went through the same thing a couple of years ago. On his a valve was stuck open.

FB

Use a heat gun to get the piston hot, it should unstick any oil in the ring grove if the ring is stuck.

Valves are free and moving fine
Thanks though

Should I just heat the outside of the engine without disassembly ?

Thanks

atf oil dribble in intake may free the ring, it s the most detergent of any oil sold, and is used by automotive shops to free stuck for frozen lifters. it makes huge amounts of white smoke too lol. i personally would dribble some acetone or MEK in the intake while running at near full throttle. its the best solvent proven to penetrate thru varnish, corrosion and rust

Post deleted, wrong info sorry!

I would pull the head off, heat the piston good, flush with fuel, then reassemble the head. ALso while the head is off, check your valve seats. You might have to lap your valves if your seats have any pits or knicks.
I would not use ATF since it will kill the regulator diaphragm if it gets that far into the crankcase.

might be a bit of crap under a valve face. while the valve moves freely, it can't seal. try to lap very lightly if you can.

ken

Heat it up, and then soak it in fuel.  Heating it up may cause them to loosen, but then the oil could congeal and cause them to stick again as soon as it cools off.  Turn it over a bunch of times to be sure to move some of that old oil out of there.</p>

1st off.... how much oil did you store it with? Ultra oil is now Mobil 1 0w20 synthetic oil and if excessive oil was use it will smoke for a while. If you feel the ring is stuck, pull the head off and submerge the top end in some raw fuel as it will take care of the goo.

Did you check the valve springs? I had a similar issue and took off the rocker cover and could see the valve springs were broken. It was not holding the valve closed; eliminating the compression. If the problem persists I would send the motor to YS service.

Thanks guys for all who replied.
This one has me stumped... the ring is fine,valves are sealing and the springs are in good shape and still no compression.
Just gonna pack it up and send it in for repair..

Thanks again,
paul