I would appreciate any thoughts on this... 2012 848evo, 3,000mi running rough abouve 95c. Compression test , engine warm, Vertical - 245psi Horizontal- 255psi Manual has good compression reading 210psi New gauge so not sure what to compare it by. Just ran through some very bad fuel. Running 90% better but still very rough above 95c Could I have slightly bent the valves (both?) Thanks
Something far wrong with these figures. 255psi would indicate an impression ratio of around 17:1 assuming no leakage! The 848 compression ratio is 12:1. so would expect around 170psi at very best. Definitely not bent valves.
I would think valve clearances would cause a loss of compression and sticking/bent valves cause high compression but I could be wrong. I did find an exhaust leak ( don’t ask about the shop rag I sucked into the exhaust). This might explain rough running at temp and noise on right side with an inaccurate compression test gauge to make sure my head stays confused…. I hope this is what it is as it is an easy fix and I have a trip on the 848 to Luxembourg in a few weeks.
Bent or sticking valves won't seal giving a loss of compression. Incorrect valve clearances will have no effect on compression unless they are holding the valve(s) open which is very unlikely.
Good point, thanks. I'm mostly satisfied that my new compression gauge is very inaccurate. Next time I pull the tank I will check with a different gauge.
There's nothing wrong with your valves, seat or piston rings with those readings! Your gauge however may be suspect.....
