Well...my 99 F4 is still having trouble. So far I have: [hr] Flushed and filled the system with distilled water [hr] Taken out the thermostat [hr] The bike only overheats when I'm riding it now, and only when I'm doing anything over 5K rpms. When left idling, it maintains temperature (no matter how hot or cold it is). The fan does turn on, but again, the bike only overheats when riding so the fan turning on or not is not the issue. I've checked the water pump, it's not leaking. And the radiator cap seallooks fine. The water is flowing through the radiator (revving it with the cap off). [hr] Things I'm thinking of doing next: [hr] Radiator cap, only because it's easy [hr]Radiator (take it to a rad shop to get tested first?) [hr] Water pump [hr] Anyone have any ideas? I'm paying monthly for this bike and it's killing me to see it sitting in the garage. Please help.

 

is the bike acually overheating or do you think it is just a bad sensor
cause it sounds like you have already checked everything else
coolant temp. sensor? maybe

 

The sensor is good. Last time I let it get hot, it started pissing water out of the overflow.

 

put a new thermostat in you need it to slow the flow of coolant and put coolant back in water is not good enough for lubricanton the waterpump any shop will tell you the same thing and water will also cause your engine to corode coolant protects it

 

-jasonp,can you speak up a little louderwe cant hear you!!!

 

[align=left]Actually, reps from any performance company will tell you otherwise. Water will only heat up or cool down for as long as it is or is not in the radiator. Water is flowing faster and isn't hung up in the engine. If anything, it would run cooler. Taking the thermostat out has enabled the bike to idle without overheating. My problem now lies in the fact that the bike overheats while at speed. [/align] [align=left] [hr] [/align]As for the water, it's distilled. It cools better than any coolant and won't cause corrosion.

 

you know...at speed, the pump is working much faster and the water will flow much faster now without t-stat. if it doesn't have enough time in the radiator, it won't cool enough before it returns to the block to take away heat.
that's why some high flow water pumps can cause overheating as well!

so by removing the t-stat, you ruled out that the pump isn't bad...does the bike overheat at idle with the t-stat in? if so then it's your t-stat may be the culprit, but also note that if your cap may not be sealing properly.

 

Thanks for all the replies guys. But this one is tricky.

At idle, the bike stays cool (fan works, etc.). I sat and revved it up to 5000-5500 rpms and held it there for a few minutes (when it was already warm) and it stayed cool. I immediately took it out on the road and it began to overheat. I pulled in the clutch cable, and it cooled down again. Back in gear, heats up. It seems like a gear or electrical problem at this point. And I checked the water pump fins, they look like new. Any more help is appreciated, thanks guys.

I can't believe it only heats up in gear!

 

Have you tried a cooler thermostat? You need to have one, cause in an open loop the water has no chance to cool down, it can only stay at operating temp(idle) or get hotter when the engine is under a load(riding).

 

i am a mechanic and i also have tried to run without a thermostat and it made things worse while driving and even worse sitting in traffic if anything try a cooler stat.water will corode your engine faster thats why drage racers use water wetter it lubes your engine and stops corosion if you insist on water then get some of the water wetter you can order it from jegs high performance or summit