How much came off the surface? Might need a thicker gasket. Since our head gaskets are limited, you may need to cut a thicker cylinder base gasket since they can be made of pretty much anything. The rest of this may be stuff you already know, but putting it in for other readers.
When you put it back together, did you check the piston to head clearance and valve to piston clearance? Lead solder in different thicknesses is my favorite because it is easier to measure. Some people like clay better. Rosin core solder compresses more easily that solid, but that means you need a few sizes like 0.060 and 0.031 inch diameter.
If you don't have at least 0.020 inch in the squish area around the outer edge of the piston, you might have problems at higher rpm. I'd shoot for closer to 0.040 inch.
Also what fuel are you running? Shaving the head raises compression and if a lot came off, then it could makes a big change in compression to where you are pinging.
The head gasket started leaking so I don’t know how much I took off but it was a lot, with a belt sander, then I trued it up with sand paper and a piece of glass, did well, went a [email protected], the gasket started leaking agin ( no oil cooler) so I took it to the machine shop, they took .015 off, the bike is e85, I get it together and around 8k you hear a noise threw the intake, I pulled the head sanded on the piston, it helped, but still had a little noise, and kept getting hot 280ish,m, plus it did not have balls, I check cam timing, with all the shaving it was off, so I redrilled the cam gear, it ran better but heck when the bike been in the 9’s in the upper 68-69 going back to mid 10’a at 64ish is killing me, lol I ordered a new piston, trying to not have to buy a brand new head, but I will if I have to
If you took enough off for the timing to change, that's a ton. Is the piston hitting the head now?
You could try using two base gaskets to bring the assembly back up, that would be pretty cheap way to check it. Maybe three gaskets, I'm assuming each gasket is 0.020 thick. Just a guess, but I think you may have pulled 0.050 off that head, sanding was probably at least 0.020.
Piston just came in, oil cooler just went on last night, timing it likes 30-32, air fuel is 12:8- 13.0, I took a lot off the head, lol my pump gas tune in my bike will run 10.6 and the bike still gets hot, same map in my buddy bike (same setup top to botom) his has ran 10.0, his bike stays 195-200 but he has a oil cooler and stock mill head, I am pretty much done with this head and would love to find another one used I can start hogging out, lmao
think I found my noise, headgasket was leaking near the intake port piston hasn’t been hitting, you can see in the last pic how much has been took of related to the intake valve
Update, measure the head cc, came out to 11.5 which would put the compression 14.8-1, I built a aluminum shim .80 to go below the cylinder, I have it back together with a new piston, fired it up but the tune was lean, I am going to ride it tomorrow
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