Ok so here's the deal. I bought this 250r in Feb of 2007, did some work to the carb and got it all cleaned up and running. I never thought to take anything apart like the top end or even just the head. he had a mutt of a carb on there so I replaced it with stock(because he told me the bike was all stock minus the pipe).
So i put a stock 34mm carb on and jetted it at stock settings. Bike always ran great!
Well just in the last few months I've been fouling plugs left and right. So I take it apart to see what the deal is and first, find that I have a broken reed....
and second, I find out that A, I'm pretty sure the piston is in backwards. B, its got a 75 on the top of the piston but it measures 66.675mm??, and 3, I think i was in the process of frying it because it had started what coulda been a major meltdown.
and here is the head, if it helps.
So, since this appears to be just a normal stock piston, what would cause it to start wearing like that on the top?? I run castor 927 at 40:1.....is it just not jetted properly or.....?