02 YZF 426..overheats on tight trails..help!?

5 replies to this topic
  • tinknocker

Posted April 10, 2005 - 10:26 PM


Hello all,
I recently purchased a 2002 YZF 426, an upgrade from a YZ 250. It is great for the track, but for trail riding I am experiencing a lot of over heating. Especially on tight goat trails. It has been relatively cool here in CA, and this never happened with the YZ 250.

Any suggestions. I already changed the sprocket to reduce speeds.
Thank you. :naughty:

  • yamahauler44

Posted April 11, 2005 - 06:13 AM


my yzf radiator boils over if i go too slow like if im stuck in the mud or something, it is normal, but annoyong. i hear you can install a overflow resivoir like on the wr's, but not 100% sure.

  • Guest_BrandonV_*

Posted April 11, 2005 - 07:31 AM


Check the radiator for buildup that could be preventing flow, check that the impeller functions properly and change the fluid for peice of mind (unless you already have).
You could always get larger rads or that Boyesen pump & cover, I've heard good things about it. Also try Engine Ice or adding water wetter to your coolant.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Dano426

Posted April 11, 2005 - 08:50 AM


The YZFs are race bikes, so you need to keep them moving! BrandonV has some great ideas. Engine Ice and watter wetter will help. I am currenlty using Engine Ice and it is working well for me. 4-5 minutes of idealing will over heat your bike, try turing off your bike when you are not moving forward. Do a search for overheating and you will find a lot of info.

Motion Pro makes a Coolant Recovery System. I am in the process of building my own, but having problems finding a good bottle?

  • sirthumpalot

Posted April 11, 2005 - 09:26 AM


As stated above, these bikes do not like to go slow. 4-strokes generate more heat than 2-strokes so they don't do as well at slow speeds where there's little or no air through the radiators. From reading here, it seems the general mods are use something like engine ice, and get a higher pressure radiator cap (to raise the boiling temp). I've suggested, but not sure if anyone has actually tried this, but if you have or can add a lighting coil and a small fan behind one of the radiators then that has to help tremendously. I'm thinking a fan made for this, such as off one of the old dual sport bikes.

  • cowboyona426

Posted April 11, 2005 - 10:04 AM


I've never really had problems with mine much. I overheated once while riding behind a youngster, and I've boiled a little bit a few times after hard runs in the desert. For sure make sure the fluid is fresh and make sure your rads aren't gummed up with anything. Other than that, just go faster! :naughty:

Related Content


The "going back to the other darkside" adventure... by Monk

Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  113 replies

05 yz450f not fast enough by RedeyeYZ

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  38 replies


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  30 replies

James Stewart back on a YZ450F by YamaLink

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 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.