HELP! I'm going nuts on this german version GY6 (REX 450) scooter

[stilkus]

Hello,
first of all I have some experience in turning wrenches and so on and I have actually worked with a motorcycle mechanic for a year. I have offered my help to a friend who owns a REX450 here in Germany.
this bike would start like a bitch and run crap rich till plugs are fouled then boom, DIE. I decided for a compression check first, I got something around 120 PSI. It wasn't that bad. I decided to adjust the valves as well to 0.05mm, both intake and exhaust. I checked the enricher and disabled it for now. A/F mixture screw didn't help as well cause the rpm has to be set high anyways for it to run. fuel pump doesn't drip as well:(. I checked the floats and they seem to close and not flood. Owner changed fuel and added something like seafoam here in our country. I gave up, so I decided for a cylinder* head swap and now I get 175 PSI compression which is impressive but still nothing on the idle.

the scooter has 3000kms on it and was stored for some time.

is there a way to let this motorcyle out of it's rich combustion misery ?