Originally Posted by cdamb
Oh I got it now. The face is warped. Not the stem?
Yes, the face is warped, the stems are not bent.
What it looks like is the back of the valve, the part that seals against the valve seat, is slightly peened over. So while the valve seals against the seat fine, this one area of perhaps 30 degrees out of 360 does not.
This is great information, Ken. I have a dial indicator and I will use that to measure concentricity of the valve stems and valve face today.
I don't know when they switched over to the valves with the thinner stems. I know the SPRs all had them, I know the Brutale 750s did not. The diameter of the stems seems within spec as do the valve guides.
Assail; from the beginning, when I first saw the bike there was something wrong with it. I ran rough off idle. The seller said he didn't know why. He said it pulled fine, it just didn't have that clean snap from idle. I had no idea what it was but figured that if the bike started and ran it couldn't be a huge problem. When I got the bike back here it ran like crap until I changed the chip that was in it. Then it ran fine until I tried to load it onto the truck for the trip to the dyno. That's where this thread started.
Yes, I said bent valves because that was the closest description I knew of. Is there such a thing as straight valve stems but warped face? Or peened over valve seating surface?
Perhaps a well nut got sucked in and got trapped between the valve and it's seat. Not bad enough to bend the valve, but bad enough to deform the surface of the valve where it meets the seat?