Recommended temp settings for my Vapor

8 replies to this topic
  • swatdoc

Posted October 07, 2007 - 11:56 PM


I'm setting up the Vapor computer on my soon-to-be street legal '07 YZ450F supermoto bike.

It has 2 warning lights that correspond to an in line water temp sensor with programmable settings. The first light/setting is the initial warning that the bike is getting warm. The second light/warning is to basically say "shut the bike down now and let it cool off before the motor is damaged".

I need your guys input on what temps I should set for the 2 warnings. Default is 190 degrees for the first warning and 230 degrees for the second. Does this seem about right?


  • grayracer513

Posted October 08, 2007 - 05:39 AM


Not to me, but it depends on what you're going to run for coolant. hose settings are probably close to right for straight water, or water with a wetting agent, but they should be higher for a proper mix of coolant. If you're running 50/50 PG or EG coolant/water, or a premixed product like engine ice, set it to 235 and 265.

The second number should be the boiling point of your coolant under the 16 psi provided by your radiator cap.

  • yama02yz250f

Posted October 08, 2007 - 07:20 AM


not to thread hijack but what would be the ideal temps for the vapor on an 00 yz426. or is it about the same?

  • grayracer513

Posted October 08, 2007 - 07:21 AM


Same regardless with all water cooled engines.

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  • swatdoc

Posted October 08, 2007 - 11:21 AM


Gray - I'm running a 50-50 mix of Coolanol/Cool-aid which was the best combo tested in an earlier issue of Motocross Action.

So with this combo, you would recommend the 235/265 settings, correct?

Would you also recommend an aftermarket radiator cap such as the one by Pit Posse that has a 1.6 rating?



  • grayracer513

Posted October 08, 2007 - 12:30 PM


The recommendation I gave is based on the boil point of the coolant I use in a 16 PSI (1.1 bar) system, which is 265. A 1.6 bar cap raises the cooling system pressure to 23.5 psi. I don't know how high that will raise the boiling point, but I would guess something like 280-285 or more. See if the coolant manufacturer can tell you.

  • swatdoc

Posted October 08, 2007 - 02:15 PM


I'll check it out - thanks Gray

Oh - any downside to running a higher pressure cap?

  • grayracer513

Posted October 08, 2007 - 03:06 PM


The higher pressure puts more strain on the hoses, seals, radiator seams, etc., but if the system is in good shape, it should be able to deal with that. But realize that there is no experience quite like coming into contact with 270 degree coolant, and you do not want to be in the immediate area when a hose blows off, so be sure all that stuff is up to par.

  • swatdoc

Posted October 09, 2007 - 01:36 AM


Gotcha - thanks.
I checked the maxima colant, and it's boiling point is listed as 265 as well, so I'll use your figures

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