250-500cc 09 WR300 Running Cold??

Hi, New Member here, I have an 09 WR300 with a license plate, and I ride it rarely on the road to get between trails, and into towns for gas etc. I've been noticing a strange thing when I am riding it on higher speed roads at about 50mph. The bike runs fine for several minutes then starts to lose power. I think the motor is getting too cold, as when it loses power, the radiator cap is not hot at all - about the same temperature as the air. If you slow down and rev the engine a couple times, you can restore full power to the engine, and if you go back to slower woods riding, the bike works completely fine again. The coolant is topped off, and the radiators do get hot during woods riding. I do all the things you're supposed to do when riding a 2t on the road, no engine breaking and vary the throttle opening to prevent it from leaning out. The engine was rebuilt 40 hrs ago. Anyone else have a problem like this? Do these bikes not have thermostats to regulate their temperature? Should I be covering one of the radiators? Thanks

'09 WR300 may not have a thermostat. If memory serves me, that wasn't stock until 2010. Someone will correct me for sure.

What is your jetting? What carb? My worry would be a lean seizure.

Heath

PWK airstriker 38... Previous owner installed it. I don't know the jetting offhand but I took the carb off and cleaned it 5 rides ago and i checked the jetting and it was the same/very similar to what others on this forum were using. Pulled the plug and it looks good.

Is it possible to add a thermostat from a 2010+?

X2 on the lean jetting. I would start there

It could also be carburetor icing. This happens in humid air when ridden at part throttle openings for long periods of time. The air speeding up through the small opening of the slide causes a pressure drop similar to a venturi or an airplane wing... ice will form and when you close the throttle or vary the opening it will melt giving your engine a dose of ice water, then once you rev it a time or two it will clean out and all is good again. Varying your throttle opening will help prevent this.

Very true. lankydoug. I hadn't even thought of that. I've ran into this while flying Cessnas, but never on my bikes. haha

I think I'd rather it happen on my bike than an aeroplane!

Would lean jetting cause the entire cooling system to be cold to the touch though?

This thread is going to move very slowly until my posts don't require moderator approval. Also next time it happens I will feel the carb to see if it is ice cold

Go with richer set up if doing high speed low rpm runs.

You should check and make sure your thermostat is not stuck closed. Mine was. I ended up dumping the OEM hoses and went with a CR style set of silicone hoses that eliminated the thermostat entirely.

no it would actually make it hotter

if the cyl is hot and the radiators are cold it's either water pump not working or thermostat stuck closed.