Overheating!!!

has anyone else had any overheating problems running at high speed on the road, w/o the thermostat in??? I was riding yesterday pretty fast on the road, and my bike was over heating... no stat in it, and I have the 1.8 rad cap!!! I read another thread, where someone said that w/o the stat, the coolant doesn't stay in the rad long enough to get cooled!!! what do you think??? :devil::thumbsup:

the coolant doesn't stay in the rad long enough to get cooled!!! what do you think???

I don't know if anyone here has instrumented this exact situation with & without a t-stat during higher road speeds to get some facts on this, but I'm sure someone will have some speculation. I've instrumented my bike without the t-stat using Evans NPG+ a few years ago, but that won't help much when trying to figure out if a 50/50 coolant mix is more effective if it stays in the rads longer via temperature controlled t-stat when riding at higher speeds. Put the t-stat back in and see if it runs any cooler. If you don't have your t-stat anymore, then go to your nearest Autozone and ask for part number '457-180' and you'll get a 180F t-stat for $4.99 that will plug & play. It sure would be nice to know the coolant & oil temps when you say it was overheating, but unless you're instrumenting this, it's just a guess. When the pig starts boiling over, it's still running cooler oil temps than the air cooled XR's I've monitored.

My bike pisses like a race horse when I stop after a TIGHT single track section. I am not talking about a little gurgling. I am talking coolant squirting straight up out of the overflow tube right under the header pipe. Riding buddies thought I ruptured the radiator. Now I make it a point to do a cool down cruise after tight stuff. YES, I plan on switching to Evans. I was thinking of removing the thermostat, just out if curiousity, but now mayhaps I will just leave it and make the switch to Evans.

I do tight singletrack all the time w/ no issues. I switched to the SRC Radiator cap and high-flow thermostat. I also use engine ice for coolant. Runs super cool. Also if you don't have the 68s pilot you'll be lean down low and cause more heat.

If I lived in Mass, I'd probably leave my t-stat in (mainly to help with warmup), but I'm often in a warmer climate and chose to leave it out. The Evans NPG+ has a significantly higher viscosity than a 50/50 mix and will stay in your rads a bit longer, but it also doesn't absorb heat as well as a 50/50 mix.

Evans does't have the thermal capacity of water or a 50/50 ethylene glycol/water mix, but....the theory is...with water in your system (50/50 mix), water will boil along the metal surface of some hot spots in your motor. This boiling further reduces heat transfer at those hot spots. Evans doesn't boil at engine operating temperatures and thus eliminates hot spots in the motor. Even though it doesn't have the thermal efficiency of water, the net effect is a motor that runs cooler.

I realize you probably know all this Qadsan. I just couldn't resist the temptation to get all technical. Imitation is the highest form of flattery.

My jetting is 172main, 68s pilot, optional needle at middle position. Bike carberates well except for sudden die out caused by rapid deceleration over uneven (downhill) terrain. I need to drop the floats a hair more to solve this, I think, but leaving the idle a little high is my temporary solution. I still have the stock thermostat in but have the replacement. I think my bike overheats due to my weight and riding style. I go pretty good, weigh 250 and abuse the heck out of the clutch. The boiling over doesn't worry me as the bike never starts knocking or pinging. Like I said, I am going to throw in Evans soon.

My pig used to piss and puke at any opportunity. Then I uncorked it and did the jet/needle thing, higher pressure rad cap, Redline WaterWetter, a 50/50 mix and put some miles on the motor. Haven't had a problem since and that includes idling for 40 minutes in a mudhole as I dug it out- didn't boil over much if at all.

my .02

what is this "Evans" stuff you all are talking about? I never heard of it... Also I had 50/50 pre-mixed, with water wetter in it, no stat, and it still boiled over!!! :thumbsup::devil::awww:

Also I'm not running a stock carb, so, I don't know what pilot jet is in it... but it has a 170 main. does any one know if keihin jets are the same for FCR pumper carbs, as for regular carbs??? :thumbsup::devil:

I realize you probably know all this Qadsan. I just couldn't resist the temptation to get all technical. Imitation is the highest form of flattery.

I love it when you guys get all scientific on us. :thumbsup:

what is this "Evans" stuff you all are talking about? I never heard of it... Also I had 50/50 pre-mixed, with water wetter in it, no stat, and it still boiled over!!! :awww::thumbsup::devil:

I noticed in your signature you have a Trail Tech Speedometer. That is why it boils over. Remove it and all will be well. :lol::D:lol:

I think there is a little confusion on the hi-press rad cap. A higher pressure rated cap does not make the bike run cooler, if you had a water temp gauge you could see that. The 1.8 cap allows the bike to run hotter before it boils over into the overflow tank.

Water wetter and a higher pressure radiator cap are one set of options I considered. I decided I will go with the evans as I feel it is the best all in one solution. Reports from Qadsan and others about monitoring oil temp with evans in use are what sold me. Now I just have to buy the stuff.

Back to Malevolent73's original question, I have no idea why his bike would be overheating at speed. I would obviously try putting the thermostat back in. I also wonder if your water pump is working efficiently? :thumbsup:

At high speeds you have a flow problem on the XR650,the

problem is you have a pressure build up in the radiator.

You have 3/4" & 7/8" tubing,the inside dia of the radiator

tubing is .900x.035,the radiator can not flow the water.

There are three thing you can do,#1 put the thermostat back

in,#2 put a restricter plate in,#3 buy aftermarket radiator.

The big names run aftermarket radiator in Baja.

Evans NPG+ will stop the boil over. Wont boil until over 350F. Moonies had the cheapest price I could find. When I changed over to the Evans I changed the T Stat and I found it bent open as I should have expected

I can't believe a lack of a thermostat is a problem. We took ours out for Vegas to Reno and added the high pressure cap and did not have a overheating problem, and that race was wide open throttle for long long stretches. And the coolant I've never head a problem with, even in my CR250 in tight d-37 stuff is Honda Coolant.

False alarm! sorry guys :D it was not boiling over after all... I had a pin hole in the small hose behind the cap to the other rad!!! which I had already replaced before with a heavier hose than the stock!!! I have the clarke tank, and it seems to rub just a little bit. the hole was just a pin size hole, but I was loosing coolant and it was dripping right on the header, and running along the side of the tank! so, I guess it was not overheating, but I did get the new stat from autozone, a whole lot cheaper than that F#@*&!G $37 HONDA STAT!!! Anyway I re-routed the hose a little so it doesn't bend right under the tank, moved it back behind the hanger plates. Hopefully that shoud do it! Thanks to everyone for all your input :thumbsup::devil::awww::lol:

I probably deserved it anyhow... thats what I get for riding a non-dualsport XR in Manhatten with an ATV plate on it!!! stayed tuned for photos!!! :devil::awww:

(China town really does have good Chinese food :thumbsup:)

On overheating:

its all too complicated for me...Engine Ice, 192 degree vs 180 degree cap, cut holes in the rear of the fender, bigger radiators, add an oil cooler, radiator guards or not, monitor the temps, re-jet--and then re-jet again...some guys overheat all the time, some never at all. Some at high speed, some at low speed. The BRP has many issues--for sure one of them is overheating....

One thing no one mentioned on this overheating thread is the clutch.

Lots of heat created when using the clutch. Those who fan it at slow speeds are more likely to overheat. The BRP can be ridden well in the tight stuff without fanning/shifting...just use the low end torque--better traction and less heat...if you are having overheating issues, now you have one more variable to factor in...

--just my 2 pesos worth--

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