Running Hot, really hot!

Took the new bike out over the weekend for some easy trail riding. About 30 min into the ride it starts acting up, losing power intermitantly and over heating, even when riding at higher speeds with good air flow I couldn't get it to stop boiling.

My thoughts were that its either something wrong with the cooling system or a very lean condition. I check out the cooling and the water pump is working fine as far as I can tell. Then I move on to a possible lean mixture. Two friends have the same bike and the same jetting and have no problems, so I rule out jetting for now. I find that my fuel hose from tank to carb has a small hole and that if I squeeze it gas squirts out. Replaced the hose and rode for about 45min with no overheating. Could that have caused the problem? Could I have caused any damage if I rode an extra 10 minutes back to the truck after noticing the problem?

The bike is a 2001 426, bought last week with 90 miles on it, air box/ exhaust open, stock jetting, riding at 6000ft. Changed the oil before riding, and after the ride.

Being newly back into dirtbikes, this is only a guess and should be taken as such...

I'm going to say that was definitely your problem. The engine would have been sucking tiny air bubbles through that hole and as those entered the carb, it would have the intermittent power loss situation you described, and as a result of the extra air in the fuel/air mixture, you would have been really lean as well. I think it would have probably been lean enough to cause the overheating you speak of too.

As for did you damage it, only time will tell. My first car used to overheat alot, and every time I did it when it cooled back down the head would warp slightly. I know this because about 4-6 weeks later it would blow the head gasket. Man, i got really proficient at changing that too... :)

Hopefully you'll be alright.

damage from overheating is normally evident immediately, so if it runs fine now with no water in the oil and no oil in the water i'd say it's ok. I doubt the fuel hose problem would cause it to run lean. If the hose was kinked, I would say yes thats the problem. If the hose didnt leak under normal conditions it wouldnt be an issue. The hose would leak fuel rather than suck air as the hose is under head pressure from the tank. Even if it was sucking air, the air would just go out the vent in the carb, and the float would maintain the correct fuel level in the carb. I'd check the fuel tank breather to start with.

hope this helps,


Overheating....I know the older WR's (yours aint new!!) did have some problems with the impeller on the heating circuit - you should maybe check if thats still working.

Thanks for the suggestions guys, I guess I'll start with the simplest first, breather hose. Whats the best way to check, ride for a while and see if preasure builds or pull the valve thingy out of the hose and blow through it?

I know the bike aint new in years, but it's new in miles!

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