2005 rm 85l melted new piston in under 1hr

hiya so heres the story i baught this 05 rm85L with no compression it felt like there was no conrod in it it was that bad so i stripped it down and found a badly melted piston the rings were melted in and there was a chunk melted from the top on the top of the piston near the exhauste port and the end of the plug was melted off and had scored the piston.

so i got the barrel buffed up and cleaned up and put a new piston ring and little end in and was running it in noticeing it was running like it was lean and i opened it up a couple of times and it cut out dead
and had little compression.

so i stripped it down to find it had melted the rings in near the exhaust and the reason for it cutting dead was cos it had melted the new plug again

so now i have put another new piston in it and wondered was was causing it to run lean ?

dinted pipe ? jetting ? airscrew ?
i checked the reeds and there ok like new and so is the water pump impeller

i noticed the radiator hose to the pump was a little kinked between the pump and the frame

any ideas anyone ??

many thanks thomas

i took the barrel to a shop and they buffed it and said it would be fine for a while without re chromeing it and it was the piston that melted and melted rings with it
its cos it running lean gettin too much air and not enouph fuel i think the jetting is stock so what could of caused it to change ?

and there it plent of plateing left on it just 1 tiny little patch that got scrached but the mechanic said it would be fine so thats nothing to with it i dont think and plus the new piston ive put in has loads of compression so i dunno ?

and when i got the 2nt new piston i got a richer jet do u think i should try that ?

cheers tom

iwas gonna take it to a shop but there all shut for 2 weeks and they re open in the new year so i thaugh i might as well try it myself and learn more about carbs in the process i can rebuild just about any 2t or 4t but i havent messed allot with carbs partly cos i havent needed to so i might aswell learn