How hot can these bikes run without engine damage?

Went for a ride yesterday in the mountains , the temp was about 78 degrees we got into some technical single track and noticed the vapor tach temp gauge was as high as 217 degrees before I decided to turn it off to let it cool. Most of the day it ran 145 degrees as long as we had a good pace.I have had this bike for about 3 months and it has a 13.5 to 1 compression piston so I know that is part of the heating issue. When it's time to rebuild I think I will put a stock piston back in. So how hot is to hot? Exracer2

217 is fine, hot but fine. I'd be worried exceeding 260.

If you are worried, add a fan.

217ºF don't seem too much for me, I've also a temp gauge at my WR and in the very slow stuff temps go up as very little moving air passes the radiators, I would stop and let cool down in the 230ºF (110ºC) area, I don't like temps above that but they happen, if you're using 50% glycol coolant and experience overboiling into the expansion tank, the water temp is more likely in the 248ºF (120ºC) area. :devil:

For the very low stuff a radiator FAN is a good idea, I had one last year but it popped, I should be ordering a new one really as the temps goes up now... (hopefully)

Edited by Hurky

Well... does the fact that these engines "boils over" into the expansion reservoir meen that the antifreeze is actually boiling ? I don't think so cause the coolant I'm using now is this:


and 136ºC (277ºF) is way tooooo hot, I think these max operating temp of the coolant is at 1.5 bar and our WR's do have a 1.1 or 1.2bar cap I think, releasing the fluid earlier into the reservoir ... or?¿

Edited by Hurky

they'll boil over, with steam coming out of the expansion bottle overflow pipe, before any damage is done

If the OP's isn't boiling over then you are in no danger of doing any damage

boil over is determined by the rad cap, not the rating of the coolant

Edited by GuyGraham

So to install a fan on 01 wr 426 I will need to convert to dc current and add a battery ? I didn't really want to add the extra stuff to the bike. But like said it was only 78 degrees and I have seen it get in to the 90's. so if that's what it takes then I guess I will have to do it! Life was much easier when I didn't have a temp gauge lol. Exracer2

If you aren't boiling over you aren't hurting the bike. Oil doesnt really break down fast until you pass 300F. Put a temp gauge on an old airhead like an XR600 and you will see some scary hot numbers.

I know how hot an air cooled engine can get. My Harley is blistering hot on a 100 plus degree days here in California. Stop lights are almost unbearable .

I found this fan kit on ebay thinking of putting it on my 2013 WR 450


Do you have the listing # and how much are they? Exracer2

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