Coolant Questions Answered

29 replies to this topic
  • qadsan

Posted June 17, 2004 - 12:47 PM


You're really kind of guessing as to whether you have all the water out of the system or not, but there are various ways to do it including steaming it out (be very careful with this option). The prep fluid they sell is probably the best & safest alternative for most folks, but I've never used it. I simply drained everything I could out, tipped the bike every which way, blew my system out with compressed air and let it sit open for a weeks or so to let anything else evaporate and then installed my NPG+. Another option that I've used for a friends KX250 & another XR650R was to drain as much of the coolant out as possible via the drain screw in the pump housing with the help of radically tiling the bike over, etc. Then I let it sit for a day with the cooling system open in hopes some more water may evaporate. Then I filled it with Evans NPG+ and ran the bike for 20 minutes to get it good and hot and drained as much of the NPG+ coolant I could. I figured this would greatly increase my chances of removing most if not all the old water/coolant and then I refilled again with the remaining new NPG+. The bike has run solid for a few years now except for my brother-in-law bending it to pieces :thumbsup: :awww: :lol:

I should also note that I'm on the west coast (warmer climate) and that I do not run a T-Stat in my bikes. The 650R t-stats are known to stick open anyway (as mine was). The NPG+ is definitely more vicious than something like HP Cool. This higher viscosity can be a problem with some applications (certain automobiles), but I've never found it to be an issue with the XR650R or some of the other bikes I've used it in. I woudln't go so far as to say it works well in all bikes because I've not personally tested it in a YZF or KTM, etc, but I've read reports from others who have.

I would still use the overflow bottle and fill it half full. I keep it there as my spare NPG+ incase I ever get low :lol:

It may be great for a SM application, but if you're racing it on a track, you'll need to make sure the coolant you're using complies to your tracks requirements.

  • big t

Posted June 17, 2004 - 06:37 PM


Qadsan, what do you need to do to eliminate the thermostat? Do you just take it out and leave it open or do you need some kind of restriction? I'm currently running the Honda coolant and haven't had any problems with overheating since I put the Edelbrock on. I would like to take the thermostat out just to eliminate a future problem.

  • qadsan

Posted June 17, 2004 - 07:03 PM


The t-stat sits inside a recessed area inside a housing so you can simply remove it and bolt the assembly back together. I'm from a warmer climate and my engine probably comes up to temp fairly quick compared to someone back east in a much colder climate. The t-stat allows the engine to come up to temp quicker which is a good thing and regulates the coolant temp as well. I would think that Honda probably did their math in addition to bench & real world testing when it comes to figuring out the optimum flow for the specs of their coolant in the XR650R cooling system. Removing the t-stat will cause the engine to warm up slower (noteably in colder environments) and will likely increase the flow speed of the coolant, which in turn will change how much heat is removed. I never pursued this further in any testing with the stock coolant to figure out how much of a difference this makes (good or bad), but its a point to consider. I've met & talked with quite a few people on west coast including various race shops who dumped their t-stats long ago, but that doesn't always make it the right thing to do. When I tested my bike with NPG+, my temps were slightly better without a t-stat installed for my application, so I just kept it out since it was stuck open anyway.

  • big t

Posted June 17, 2004 - 08:54 PM


Thanks qadsan. I was wondering if no restriction might actually make it run hotter with stock coolant. I guess I'll see how it does this summer in the heat here in Memphis.

  • qadsan

Posted June 18, 2004 - 05:27 AM


Hi big t. I just read my post from yesterday about this and I was rambling...sorry :thumbsup: I was super tired, in a good bit of pain and not thinking too well. To better answer your question (hopefully), I honestly don't know if removing the t-stat will make it run hotter with the stock coolant or not for your riding application, but I don't think it will make a drastic difference either way once the bike is warmed up. The t-stat housing is o-ringed, so you won't need a new gasket when you remove it (unless the o-ring is damaged), but make sure to drain the coolant first or things can get a bit messey.

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  • airport4

Posted June 18, 2004 - 05:43 AM


Question for you XR experts, when the stock t-stat fails does it fail in the open or closed (no flow) postion?

  • qadsan

Posted June 18, 2004 - 06:01 AM


It always fails open, but you can bend things back to fix it. I've never heard of it failing in the closed position for our bikes...thankfully.

  • SaltyWalrus

Posted June 20, 2004 - 05:38 PM


While checking up on Evans I learned you can flush out the system with Sierra anti-freeze to help remove all water before installing Evans. I think it was the Evans web site itself I got this from.

  • longhorn454

Posted June 26, 2008 - 10:30 PM



Instead of getting crazy with the bike by laying it on its side to get all the water out, couldn't you flush with there kit pull the radiator's blow out with air & sit them in the sun each day for a week wile blowing out with air every so often. Then refill with Evans run for a season flush and refill again. (overkill)

  • martinfan30

Posted June 27, 2008 - 07:28 AM



Instead of getting crazy with the bike by laying it on its side to get all the water out, couldn't you flush with there kit pull the radiator's blow out with air & sit them in the sun each day for a week wile blowing out with air every so often. Then refill with Evans run for a season flush and refill again. (overkill)

Qadsan has not been active for almost two years. Check the post dates.

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