overheat

Hello Gurus, Cracked open an old Suzuki sled engine and thought I had found the problem with it. Overheated crank pins as visible here Then a closer look showed no such discoloration on the needles. ¨Could´ve rubbed off¨ I thought. Next, once the crank was out, a better look overall showed...

2004 RM 250 running hot. 8 months back I rebuilt the top end with a Wisco pistion kit. The bike ran hot for a while and then seemed to break in and cool down a bit. It seems to be back up recently. The symptoms are uneven reving (pinging) and then after that it runs off...looong reving. I...