My bike blows antifreeze out of the overflow after only riding for a short time. Any suggestions for me on what I should check/repair?

Just got my bike so I don't have a lot of hours on it. Usually if I'm going slow on the trails or letting it idle too long is when this happens. Sorry I don't too much about the maintenance side of this but I'm trying to learn.

[ July 30, 2002: Message edited by: steverox ]

we need more info than that! Are you riding a track and keeping air moving throught the radiators, or are you in the woods on tight single track with lots of slow sections and hill climbs? Let us know when the problem is hapening. Then we can help you out.

My bike doe's the same thing when it gets hot. When i let it warm up to long it will blow antifreeze out. Thats normarl.

Mine does the same thing-of course it's always after I just get out there for the day-that's b.c I just topped it off. When I first got it I would let it idle int he garage b/c it sounded so cool, and I thought it was going to blow since coolcant was coming out-rode for 1/2 mile and all was well...I figure it heats up and boils off what is excess. After a day of riding, you should see how much it takes to top it off again and see how much is really being lost. With no overflow, there is no way to prevent some boiling over if it's topped off when cold. I'm sure you already know, but DON'T check it when it's hot...

I think a big question is, is the bike spitting out only a little bit, or is it boiling and really blowing it out? If you can hear it boiling and/or it's really blowing it out then it sounds like it really is overheating for some reason.

This makes sense because you're on slow trails or idleing, neither of which moves a lot of air through the radiators. The next question is how to prevent the problem. If you don't find a good answer in this forum (I would be surprised) then be sure to check out the WR426 forum. I'm guessing there are more trail riders there and they should definitely have info for you.

steverox after you ride and loose coolent let the bike cool down then take the cap off and check the level.

If the coolent is still above the core tubes dont add any. (put the cap back on)Ride it like that and see if it overflows again.

Then tell us what happen's


Ok here we go. These bikes are built for MX. that means flying around a track for about 30min. at a time and constant air moving throught the radiators. When you get into the woods and start slowing down, no air is moving throught the radiators (well minimal air anyway).

Here is what you need to do.

1- Run "engine ice" or "water wetter" in the radiator, this will bring down the operating temp any where from 10-25 dagrees.

2- If the bike is really heating up, you hear it boiling and it's runing like niagra falls. Stop and let the bike cool down. Take beer-30 and relax for a while. I usually wear a camel back for me and I use the water to top off after this hapens to me. I usually go on long rides and I don't want to have to ride 1hr. back to the Jeep to top off the radiator.

3- If you still are having problems and really want to handle it once and for all this is what you do(and what I did by the way).

The WR model comes with a radiator overflow bottle. It resides under the left # plate. Instead of overflowing onto the ground it overflows into the bottle and when the bike cools back down it sucks the fluid back. It works very well. You can either make a mounting bracket for it or trade a guy with a wr for his sub frame. the wr sub frame is made out of steel vice our aluminum sub-frame. but there are wr guys out there that don't like the overflow res. and would be happy to trade their sub-frame and resivour for your aluminum sub-frame. I traded a guy, he paid to ship me his sub-frame and I paid to ship him mine and that was it.

Good luck and stay COOL!!! :)

Well my local thumper mechanic would say "if its getting to hot, then your going to slow" :D

And its no wonder why he told meeee that :D

I do know, you cant let these bikes sit for any amount of time, specially for those bike to bike BS sessions, your just asking for an over heat.

Tight trails will get her hot, thats a fact.

I just bought an $8.00 dollar bottle of watter wetter to see if the stuff really does work. Everybody seems to like it.

But without foolin with the raditor or makin an overflow bottle, the only thing I can suggest is to GUN IT :)

Lots of help eh.....


I mentioned this before but I still don't know if anyone tried it, let me know how it works if you did.

If you're really hard-core about trail riding, I would think that you could add a lighting coil and a small thermistat controlled fan (like from a road bike). It shouldn't add more than a couple of pounds and you'll always have air through the radiators when you need it. Has anyone tried this?

Use "Engine Ice". My best friend and I always have 6-10 rugrats with us when we go for a ride. We always have to ride for us then come back and take the little ones for a ride.

He leads on his 426F and I bring up the rear on my 250F. We ALWAYS overheated considering the creepy crawly pace.

Then we changed to "Engine Ice" and neither one of us has ever overheated since. It's a bit expensive but very much worth it.

Just my $.02 worth!


I've been trying different coolant mixtures in my bike. 50/50 distilled water & ethylene glycol was making my bike puke in low speed, high temp riding. I then tried 100% distilled water with Watter Wetter. It still puked. After talking with an HVAC engineer, I then tried 75% distilled water, 25% ethylene glycol, and Watter Wetter and haven't puked coolant yet. :)

BTW, I ride woods only on my 426.

Couple of things...

If you have one of those metal radiator protectors, TAKE IT OFF...they block way to much air flow and that kills the cooling performance...avoid using them if possible.

Also, when you change your coolant, do a good flush of the system. We recommend a 50/50 solution of Water and White Distilled Vinegar (Both avail at grocery store)....fill the system with the flush solution, run the bike til warm, let cool, drain, rinse system with clear water. It scrubs out any mineral deposits that may be hampering your coolant flow as well as scrubs off the film build-up of the old coolant in the system. The film-like coating that can be left by some antifreeze products acts more like an insulator and keeps the fluid from doing its job effectively.

The water (75%), EG (25%) and Water Wetter is a good do-it-yourself mix, but it will have a somewhat low boil point and minimal freeze protection. Water and Water Wetter is an excellent cooling combination and works well, but again, a very low boil point and zero freeze protection.

I'd hope you'll try our product, but at least now you have some good information to go on.

steverox I use 50%/50% mix of antifreeze and distilled water plus water-wetter.

I also use header wrap on my head pipe to keep the heat away from the raid. and hoses.

I've been trail riding here in 95+ deg. and 70+ dew point and 70%+ humidity, with no over heating problems.

If you fill the raid. to the top wen cold it will spit some out. as long as the level is above the core tubes in the raid. wen cold you got enought coolent.


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