New overheating problem.

I purchased a used 97 220 this winter and on one of the first few rides in very low ambient temps my 220 overheated, while really overrevving it to get up a snow covered hill. It got hot enough to blow out the plastic plug on the left radiator. I just assumed it was a one time deal, as it has been o.k. since in warmer temps.

In the last few weeks at two different enduros in the Northeast, the bike has overheated to the point that it actually blew out a coolant hose on each ride. The first time I figured it was a weak hose, but after the second time I need to figure out what is going on.

I believe I may have caused my own problems, as I installed a stock 200 35mm carb jetted 45/155 and maybe I am running lean. Could a lean condition get the bike hot enough to blow a hose? The bike has a pipe, drilled air box top, Boyeson reeds.

I will pull apart the top end Sunday and check the water pump impeller also.

Well I found out what the problem was, i'm happy but feel pretty dumb. After pulling the top end and finding all was well, inspecting the water pump impeller and changing the seal, running engine ice, water wetter and ordering Evans NPG (but didn't get a chance to try it). I found out that the radiator cap was not releasing pressure, changed 10.00 cap, all is well.
That was a very expensive lesson, I had been reading all the 220 overheating threads and expected the worst, overlooked the basics.