Will a valve 're-seal' itself?....

[crazy steve]

...As thin as WD-40 is, I don't see that filling/sealing any air gaps to increase your compresion much at all.. let alone 70-80+ points. I think you just got some rust or carbon wet and squishy or it loosened something up a bit. A burnt valve, and you won't get compression numbers like that.

According to the PO, this bike had been running up until very shortly before I bought it, although the PO admitted it ran poorly. He quit riding it when the number two header broke off at the flange and fell off...

I have to stress just how tight these valves were; I went four shim sizes down on the #2 exhaust (increasing clearance by almost .008") to bring it into spec so it was under .002". This one came up to match the others, a gain of 85psi or almost 100%. But #3 needed five sizes smaller (almost .010") to get to spec, so it was just barely closing, maybe not quite all the way. This one did come up to 150psi (from 60), but I was 25psi short of matching, and outside the 'preferred' 10% allowable variation. That's when I tried the WD40; I gave the closed exhaust valve a small squirt in through the exhaust port (just enough to see that it ran around the full circumference of the valve) and tried it again. Bingo, I got the same 175psi. But this only worked for one test; to repeat the test and get that number, I had to give it another shot, otherwise I was back to the 150psi number. That's why I used the WD40; being as thin as it is, I figured it wouldn't seal any real damage, but if it were minor enough it would at least temporarily.

So that's what leads me to believe that the valve may be very slightly burned, although TCs' thought that there may be some light carbon deposits on the valve/seat may be a very real possiblity.

I'm going to let it go and install the motor; after running it some, I'll recheck to see if it at least comes up to within 10%. This is a bit of a testament to how much abuse/neglect these will take...

[BA80]

Give it a shot Steve and see how it does in the real world. If it's no good I have a good XJ head I got last fall that the YICS ports are already tapped and plugged I'll let you have for a good price.

[crazy steve]

Give it a shot Steve and see how it does in the real world..

That's the plan Greg. I think it will recover after some miles, at least enough to get within 10% of the others.

Next on the agenda is the 2nd gear fix... I've avoided this up until now, time to break my cherry....

[BA80]

Next on the agenda is the 2nd gear fix... I've avoided this up until now, time to break my cherry....

I've never done the dremmel thing but I've taken the secondary shaft out and replaced it a couple times. That part ain't no big thang.

Do flip the bike though or you'll wish you had

[crazy steve]

Do flip the bike though or you'll wish you had

The motor is out and on a rotatable stand, so that part is covered...