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

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:

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.

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.

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?

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.

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:

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