Went riding last night in somewhat marginal conditions and after about 60 miles my 97 xcr600se ran the temp gauge to the top with only about 1/4 mile left to get home. I shut it down and trailered it from the place where I noticed it. It ran fine and not once got anywhere near the hot region of the gauge all night. So I thought that the last 1/2 mile we rode may have not had enought snow, but it was like everywhere else we rode, so today I ran it around the house after I topped off the coolant and bled the system and whammo, after about 3 laps it ran to the top of the gauge. I pulled the thermostat and put it in boiling water and also at about 140 degree F water ( since it listed 120 on the thermostat ) and it opened both times, so I assume that is fine. So, what next? I will check the cap, but can they just let go all of a sudden? Also I have read some water pump stuff about plastic gears and sight glasses with oil levels and was unaware of these things on my sled. By the way, the coolers are cold and some of the hoses that run to the coolers are ice cold, but the bottle is bubbling over. Any suggestions?

are u sure that u got all of the air out of your system when u bleed it,if i were u i would put a new termmostat in then u know

I don't think bleeding is an issue yet since the sled overheated on its own. I have never had the cooling system apart to allow the introduction of air into the system. The coolant level has always been good without the need to add any. I think I need to determine the cause and worry about the bleeding later when I get it back together or for testing. A funny thing I noticed is that the temp gauge was buried, but the dash light never came on. Does the dash light function if you have the guage option or is it disabled? How could I test this along the way? Just a thought, maybe the dash light sending unit is in a different location where the less hot coolant is. I will have to investigate. I say that because as my reservoir was boiling over I had coolant hoses that were ice cold. If the pump wasn't pumping would I have the reservoir spilling over when I remove the cap? It does spill over when running with everything cold.

If your temp is going up but hoses feel cold then I'm thinking the water pump or thermastate.

My dealer has no parts on hand, not even a gasket to put the stat back in. I will get some sgasket material and cut my own. They suggested that I check the plugs for coolant also. I will do that tonight. I thought about running w/o the stat inas a test, but would that screw up my coolant direction since the stat controls two paths which appear to be a warmup and a normal temp path? I guess for diagnostic purposes it would be better than nothing. Still looking for past experience from others if there is any. Conditions here are crappy with possible snow on the way, but the dealer says three days for a cap, stat, and gasket. Ouch.

I had a similar overheating problem on an RMK 700... after frying three pistons and two cylinders over 30 miles, and paying the shop to fix it, I tore it down and found the NUT that is supposed to be on the impeller in the water pump had come off! It would cool at idle, but at anything higher than that, the impeller shaft would just spin inside the impeller! If the exchangers are cold, then there is NO flow..you have a restriction or a broken/malfunctioning pump, or the thermostat is not allowing fluid through... You also may have broken a belt...a failed water pump belt would act like this too

How hot should the exchangers be???

Water pump

After spending about 4 hours burping and bleeding the system through every orifice,I now know there is no air in the system, which rules out my theory (wishful thinking) that I had air in the lines. I am leaning towards the pump problem due to knowing that the thermostat is opening and the lines close to the head and thermostat housing are getting hot. Six inches beyond the motor and all lines are cold, so I agree with the no flow / pump problem. Also, it can stay at medium to very warm temp at low rpms, but gets hot fast at higher rpms. Anyone in NE and Northern Wisconsin should be thanking me that my sled is broke since every time I have had trouble this season we have been dumped on with snow. Good year for snow, bad year for me riding. Thanks everyone so far for all the help.

Also check the water pump belt.. that happened last week to a buds sled.

From looking at some exploded views on the web it looks like my pump impeller is gear driven off of the crank, so I will ckeck that out. I am not sure if it will be metal or plastic, but I have heard the teeth can break off on the plastic ones.

If anyone is still reading this I finally figured it out. I had a bearing in the water pump sieze and it melted itself to the pump shaft. The heat caused the plastic gear that is driven by the crank to melt loose from the shaft which it is molded to. So, the gear was turning but the impeller wasn't turning. I originally mistook the air burping and boiling as pump flow. Well, now I am off to the dealer or a salvage yard for a new shaft. Thanks everyone for your help.

Good to hear problem solved. How big of job does it look to be??

Not too bad actually as far as location and work. I had to remove the pipes, but that was about all besides having coolant all over the floor. The melted plastic did leave pieces inside the pump housing on the engine side, but got those cleaned out. Now, is the chamber that the drive gear is in sealed from the rest of the crankcase or did my plastic pieces get into the crankcase? it looks like a separate cavity, but also has a port that looks to deliver oil/gas for lubricant. Any info on this?

Thanks