wr426 trail tech vapor temperature readings off???

Hi all,

I have an 02' wr426 and it seems to be running hot when I'm climbing single track in 1st gear. It runs at 160F if I'm running down the road getting lots of air over the rad. When I'm running slow, it tops out at 265F but doesn't boil over. I'm riding at ~6000-8000'. The bike runs fine, doesn't lose power or anything but don't want to blow it up. I'm wondering if the computer is reading correctly. Yes I have it installed correctly on the outlet side of the engine. Will the antifreeze boil out of the boilover container when the bike gets too hot? It seems to get hot real quick. The rad is clean/clear and the cap is good. The system is clean and has been recently changed with Honda premixed 50/50. The bike has very little time on it, ~800 miles. Could the jetting be so lean that it causes it to run this hot? I called me local dealer and they said 160F seems too cold and 265F seems too hot to not boil over so they too are wondering if the trail tech is reading correctly. Please help, I don't want to blow up my nearly new bike!! Thanks for your input!


Sounds pretty normal to me. Climbing first gear single track these things get hot. I have my Vector sensor on the rad side (cooler) and in tight single track my temp is regularly in the 240-260 range with a 1.6 cap (1.1 stock) If it's long enough without opening up I boil over at around 265-270 and I've shown a max temp of 290 racing (lost lots of coolant)

Meanwhile if I don't warm my bike up with some slower riding and just jump on some faster stuff I have trouble getting my bike up to 150.

do you have any coolant comming out of your overflow hose?have you ever done a pressure test on your radiator cap to make sure it is opening at correct pressure?I have a yz400f and i lose a little coolant out the overflow but not much,my bike is all stock I have never messed with pipe or carb.

Hi, the cap has never been checked, but the bike only has 800 miles on it and nothing is coming out the overflow. The bike has a stock pipe with the end removed, the airbox top is removed, it is setup with advanced yz timing and the throttle stop is cut. The bike rips, it just seems to run hot or thats what the trail tech vapor is telling me??? My plan is to keep riding it and ignore the temp. The previous owner said it was jetted for 8000+' and sometimes I ride it at 5000'-8000'. This would cause a lean condition, but could it cause the bike to run 265F? The bike has plenty of power even when hot. The header pipe never glows or at least I can't see it during the day. Thanks for your thoughts!

That sound perfectly normal. These bikes run hot, but that temp sounds very normal to me anyway.

Thanks for the replies!

So no worries of overheating and warping the head or blowing the head gasket? A local dealer said if it were running too hot for a while, it will cook the oil and then the valve guide seals and then I'd be riding a blue smoker, oil burner.


My 01 426 Vapor reads 250 at the most. But then again I dropped to a 13 front sprocket so most of the hill climbs are in 2nd.

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