Valve lapping ?

[GLoweVA]

100psi ! I'd be happier than a pig in S#!t if I had that in #1 and #2.
My numbers are all over the place.
In a cold engine at TC's after the muffler repairs, I had something like: 50/60/120/130.
We put oil in 1&2 to see if they'd go up any and nada (Not much at all)
We thought valves, so I ended up swapping the head with the G and I've still got the same symptoms. (I reused the same head gasket. )
Funny thing is WHEN it finally does catch and start, it seems to run okay.
I'm thinking that the combustion in 1 & 2 are somehow helping to seal up those cylinders and thus the bike runs on all 4. (not pretty, but I do get her up to 75mph at about 5k rpms for the 30-40mins to get home)
I'm not getting any blue smoke out the pipes, but I was getting a little oil leakage from around the head. That's hard to track down to an exact location though.

One of these days when I get home from work and it's still light out, I'll try to get some hot compression readings right after I pull into the carport and see what those numbers are like.

Anyway the whole reason for this thread was I wanted to make sure the SG head was good to go before I put it back on her. (with a brand new head gasket. )
That way I know the top end will be good to go and my compression numbers should be okay then. (Unless I do have bad rings. )

Maybe I'll borrow TC's compressor and try a leak down and see if it'll tell me where I'm leaking.
I figure with about 90-100psi into the plug hole, air coming out should be easy to find wether it's the gasket, rings, or valves, right?
(assuming the piston is in the right postion for the valves to be shut.)
(the G's head's valves should be good, at least I think so because it ran fine on the G)

[skids]

George. I am almost certain it is more tuning than compression oriented. My SH compression readings are all around 100 PSI give or take less than 10%. I get anywhere from 34-40 MPG out of the bike. YMMV...literally.

I have one with fairly low numbers also. 100 to 115 psi if I remember correctly. It does just fine in town at a mile high, but the tops of mountain passes at 11k feet, the engine has troubles. Less ambient air density with low compression numbers is trouble.

[mack]

Lapping

Here is the stuff I've used, I'd imagine it's the same as TC's


The way I did mine on the LH (because the seats didn't have much left on them) was to sit with a dental pick and solvent and clean the seats as good as I could before I even started the lapping process.
I then worked on one side at a time doing just the absolute minimum. Ten rotations, lift then ten more. Clean the valve and seats up really good, reinstall the valve and leak test with solvent. The ones that still leaked I repeated the process until I had no leaks. I never lapped until I had a clean shinny strip on the valve. Just took off enough so they seated and didn't leak.
I then repeated for the other side.
After the valves all seated with no leaks I, blocked up the head, put in a cam and checked all the clearances. Pulled the cam again and changed out the shims I needed to and wrote down the numbers and reinstalled the cam then checked the clearances again and wrote the new number down and removed the cam again.
Repeated this for the other side, then reinstalled the head. Once done I checked the cold compression numbers for each cylinder and recorded them.
Here is what you'll have. I keep this taped to the lid of my tool chest for futre reference;


Now that the motor is breathing properly, it can be tuned properly and with- in a few hundred miles, your compression numbers will come up if the rings are still good. Recheck the hot compression numbers and write them down for future reference. My numbers are all right around 180 now hot.