Mr-unorigonal

The motor is built but the person who built/had it built passed away so I've had to figure it all out myself. I didn't want to pull the head if I didn't have to but I might. Are there markings on the domes that would tell me what they are?

So I've had this bike for about a year. It's the only quad/bike I've owned and although I've leaned so much just from research and hands on I decided to take what I found and get some more experienced opinions. So this is what you are dealing with. Cheetah Cub 443, 7mm stroker. 110 octane 32/1 yamalube. 35mm TMX Mikuni carbs. 27.5 pilot 310 main on the richest clip setting. The problem is it only makes 140psi compression (cold). Being that the bike was built to run race gas those numbers seem a little low. I don't know what size domes it has but regardless it just doesn't seem right. Also the past few times I've taken it out it had started running pretty poorly (Rich) which from what I read can mean the compression is dropping. I've raised the clip 4 slots and it finally sounds happy in the mid range. I've ordered some mains and will update once I get it happy on the top end. So my question is is it possible that the bike always ran lower compression (unlikely) or is my top end going out. (Likely) This is the bike (first clip was when it was running good) and the first 3 gears were slow, was on sand geckos. The other bikes were 450's https://youtu.be/XYoRKYh0qaA Also put pictures of the pistons and the bike in there. (To big to attach) Any input would be appreciated. Thanks in advance.