99 YZ400F radiator issues

8 replies to this topic
  • PatrickM

Posted April 05, 2007 - 01:20 AM


While riding my YZ400F this weekend, I noticed a bit of steam coming from the botoom of my bike. Naturally, I shut the bike off and checked what was going on. I come to see that the radiator overflow tube ends right under my skid plate (under the engine and on top of the skid plate). I guess the tube leaked out some radiator fluid on the skid plate and since it was close to my engine, it steamed up

My Question is......it the radaitor overflow tube in the right location (stock one) and does anybody know how I can re-route th tube to end out with the rest of the tubes that dump out at the back of the transmission???

Also..... does anybody know the diameter of the radiator overflow tube???

Thanks for all the help!!!!!

Patrick M.

  • jayh300

Posted April 05, 2007 - 06:39 AM


i think that is where mine is on my 99. 2 questions... were you riding slowly, if so those have a tendency to overheat. Also... what coolant are you running. i put engine ice in mine and also don't fill it up all the way. my manual say to, i was told not to. everytime i filled it all the way up, it spit a little out. fill it to just below the top and mine never spits any out.
the no air flow on those will sure make it overheat. could also be a weak rad cap. might check that too.

  • kylwk1500

Posted April 05, 2007 - 06:51 AM


you could rerout it, but i remember my 400 overflowing just about evertime i rode. they are pretty tempermental to heat. i put an overflow tank off of a WR and it fit perfectly, and worked great. Check out my garage for pics

  • PatrickM

Posted April 05, 2007 - 11:12 PM


ok that all makes sense

First, I have the radiator filled to the top (where the manual says to). at this point I am running regular radiator fluid (green anti-freeze and water at a 50/50 mix)

Should I change the fliud to Engine Ice????

when you talk about having an overflow tank for a WR, what year WR's have this and would a Yamaha Dealer sell them????

one last question for everybody....

is it possible to just run pure antifreeze (green, pink, or blue)....is that what engine ice is???

thanks for everybody's help!!!!!

Patrick M.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jayh300

Posted April 06, 2007 - 07:52 AM


engine ice is a pre-mixed coolant that is supposed to help the engine run cooler. not sure on the year on the wr tank, but i have been looking for one for my 400 also. the first time i really rode my 400 in some very tight trails on a hot day, she puked coolant everywhere. did a lot of reading. I put a new rad cap, flushed and filled with engine ice, and really watch my ride speed, not to slow,no air flow, and have not had any more problems with it.
if we stop for any time at all, i shut it off. oh yeah... and don't fill it all the way to the top.

  • PatrickM

Posted April 06, 2007 - 09:40 AM



I think i was going slow enough to get the engine too hot!!!!

Thanks for all of your help!!!!!

I will have to change the radiator cap, convert to engine ice and keep looking for a WR radiator overflow tank

how much does Engine Ice cost???

Patrick M.

  • jayh300

Posted April 06, 2007 - 09:48 AM


i think it is in the 10.00 range and the bottles are 1/2 gal. i think.
1 jug did mine. not sure if there is an aftermarket cap available. the oe yamaha cap was like 30.00.
have fun

  • PatrickM

Posted April 06, 2007 - 11:24 AM


where could i find an aftermarket radiator cap???

an websites or parts companies to look for????

Patrick M.

  • jayh300

Posted April 06, 2007 - 11:38 AM


pit posse does some, bike bandit does oe and aftermarket stuff.
pit posse seems to be quicker on shipment to me.
and of course ebay and thumper talk store

Related Content

WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

First Hare scramble tips by dhend8

Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F

Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.