ec300 radiator boiling over

[stainlesscycle]

so, lately my bike has been boiling over occasionally during races. usually when muddy and hot. i replaced impeller with checkpoint one, replaced seal, and put new coolanol in it. i don't overfill the radiator, and i have no recovery tank. i checked radiators when it was boiling today and they weren't caked with mud. when i was running the 200 with same radiators it never ever boiled over.

i'm guessing the cap is bad maybe?

what cap works best 1.4 ktm? i bought an aftermarket one a week or so ago, and it would not fit my radiator.

and the second question is this:

when boiling over, better to shift down and up the rpm's so coolant moves faster? or shift up and lug it so piston speed is lower (less heat...). i can't increase airflow (go faster) - if i could i would

[jhendr3702]

i am running a ktm 1.4 on my 01 300... it will still boil over a little.. esp in really tight no air flow situations.. 95% of the time it is fine.. it only pukes out a couple of drops.. it has an ltr impeller also..

in my pea brain, i would think you want the coolant to stay in rad's as long as it could, and slower piston speed and less heat.. but i sure could be wrong..

[Brian VT]

I've got some very long climbs here and I often boil the coolant.
I wouldn't loose enough to be concerned with. It would just drop down to where it just covers the fins and it seems fine to leave it there.
That said, I was always a "lugger". This year I've been doing those long climbs in the next lower gear. I just hold the throttle at 3/4-to-full and work the clutch instead of the throttle. My bike hasn't been boiling at the summit and I think I've gained some speed. If not, at least I sound like I'm going faster. LOL

[stainlesscycle]

mine "steamed" out the cap for a minute or longer twice today...... it wasn't going out the overflow hose. so the stock cap is toast im guessing. haven't unloaded bike to clean/check and see how much coolant i lost..

[GMP]

You can try the inline coolers, I never boil my 250 with them even in slow technical going, and lately riding with kids. If it became an issue for me I'd switch to Evans coolant like I did in the 4-stoke.

[mikeh]

1.8 rad cap took care of all the problems of over heating and fluid loss and we ride 40to 70 miles on tight singletrack up neverending hills in northern cali with temps into the 100's i use water wetter in my coolant mix and change it once a year.. I have an 07 EC300 with new top end after 4500miles and it still purrs

[GasGasDreamer]

Originally Posted by stainlesscycle

mine "steamed" out the cap for a minute or longer twice today...... it wasn't going out the overflow hose.

that doesnt sound right. even if the cap was releasing the pressure to early, the vent is were the pressure comes out of. maybe check that line. it should be clear and have no kinks, etc.

also, putting on a higher psi cap also raises the motor temp. so even thoug you may not be 'boiling over' on the outside, its hotter on the inside.

also, on my 06 ec300 there is a plastic bottle that is, i believe, and expansion tank. what i did was order another one and mounted it above the stock one and routed the overflow line into it. you have to block off on side

[GMP]

I got rid of that tank its just one more thing to fail. Stainless, just get a new 1.4 bar KTM cap and you should be good. The stock 1.2s always weeped. If your not too lean and still have trouble switch to Evans.

[stainlesscycle]

i put a 1.4 on it. will see if it boils this weekend.

[bchatt]

I believe lean jetting is a common cause of overheating, but not often diagnosed......