XR300 Running Hot...

I had my XR300 top end done by a reputable shop near the Elsinore track. I haven't ridden it much, but recently took it in our local area of tight slow single track. Outside air temp was around 100 f. The bike peaked at around 300 f and didn't really cool down even when we started moving pretty well. It never ever ran than hot before the rebuild... Prior to the rebuild, even in the heat of the summer in the slow nasty stuff, it would peak out at about 250 f.

My son changed the oil, and I decided to check the plug and found that it was loose.... I installed a new plug CR9 R and went for a short slow ride. It never got over 250 f.

Do you think the loose plug could have been the problem??? Or should I keep looking... Any advice as to what to check next would be appreciated.



loose plug should probably cause a lean condition,

a loose plug will certainly cause valves to burn

a new rebuild will run hotter for a few rides

personally i would not worry about the oil being 300F , if your using the right type of oil there should be no reason for it to breakdown after a ride or two.

no cause for alarm in my books


it was the spark plug that let more air be sucked in, thus creating a lean condition.

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