Another coolant system question

Since a 1.6 ATM radiator cap means 23.52 psi and Honda's manual says do not exceed 20 psi, is big-money damage to my BRP ('01 XR650R) possible using one? Of course I already bought the cap (not yet installed - looks the same as stock) from XRs Only and expensive EngineIce pre-mixed coolant. Thanks for the info.

Why did you buy a high-pressure cap? Was it overheating? I have read lots about the boil-over on the XR650; bottom line is that if jetted properly and uncorked it will not boil-over with the stock 1.1bar cap. A high-pressure cap puts lots of extra strain on the cooling system. Unless you race and can afford the repair bills I would not put a high-pressure cap on the bike. I would look into why the bike overheats, not just band-aid the problem with a high-pressure cap.

I still run the stock cap and have never had a boil over problem with the BRP. If it ever did get that hot I would much rather lose some coolant than blow out a hose.

I agree, I have ridden in some pretty slow (1st gear, rock hopping in pretty warm weather) type of terrain and haven't had any problems. Also as stated, if jetted correctly, you shouldn't have any problems.

A little more background. It's never overheated on me, I only bought it last November. The original owner (a Honda m/c mechanic so it's well-tuned) removed the overflow reservoir and did most of the mods. I know that if you leave an XR idling on the side stand it will eventually overheat. My '89 XR600 (air cooler of course) took a lot of hard riding @ slow speed in 85° F weather w/o complaint. I was just being macho in buying the higher pressure cap to fix a problem that hasn't happened and wanted to ask others before I did it. If you know damage is possible to the internal system then I should rethink this process. Thanks.

I have rode my big XR for the last two summers in Utah's hot deserts. I have never had an over-heating problem. I have heard that others have had this problem, but I have never experienced it. The only modification I have is the power-up. I agree with some of the others, if you have not experienced any problems, maybe you shouldn't worry about it.

2001 XR650R/Power-up.

Just out of curiosity, what are you guys running as the "coolant" along with the water to the system? I'd make sure that you use distilled water in the system instead of tap-water. Distilled water is very friendly to aluminum and radiator parts; whereas, tap water usually contains chemicals that over time will deteriorate and eat away at the internals. In car racing applications, I've used distilled water only, with great results. Removed the thermostat, and made a plate out of aluminum with a small hole in it to slow the flow thru the radiator for cooling purposes. I'm not familiar with the BRP's cooling system, but most thermostats tend to fail in the closed position. This might seem trivial, but does anyone make a slow-speed cooling fan for it?

I've had boilover problems while running thru some slow stuff during hot weather, but that has been reduced(but not eliminated) with the Engine Ice I'm now running. I would never remove my overflow tank, when you do have a little boilover it holds the coolant until things cool down a bit. I've left my thermostat in, but I still sometimes worry about it sticking closed, so I might take it apart this summer, and just run the housing with the most of the guts removed, leaving a small restriction to slow down the coolant flow for proper heat transfer.

Still will not run the hi pressure cap... :)

Taking the guts out of the thermostat isn't enough restriction to slow the flow thru the radiator. Someone needs to install a small water temperature gauge preferably mechanical, so it reads constantly, and test the waters so to speak. No reading could mean no water in the system(mechanical gauges don't read air temps.). Too high a reading could mean a stuck closed thermostat, or it's about ready to blow! If there isn't any air flowing past the radiator, then it is bound to overheat. How does anyone know how hot their bike is running other than a boil-over telling you that it is too hot? I'd have to know if I had a water-cooled bike. Mines oil cooled only, and I love the oil temp dipstick. I know my oil temp all of the time. Something to think about.

If your bike has the Honda Power-Up kit properly installed, and running a 175 main jet at 1000' or below, or even a 155 at 5000' or above, the bike will not overheat/boil over. Mine has never boiled over, even at low speeds going up tough mountain trails in the summer. I honestly don't know how people are boiling them over. The guy I bought my bike from (it was stock at the time), said it would boil over some when riding slow. Sure, stock it will, it's just too lean. But changing the radiator cap if the bike is uncorked is not necessary. I have over 4000 miles on my bike now, and it's never overheated or boiled over. Don't idle it more than a few minutes during warm up period, and there should be no problem.

As far as what coolant to use, I use the Honda pre-mixed 50/50 coolant, and have never had a problem at all. In fact overheating is the least of my concerns.. Keep the oil changed regularly, keep the air filter clean, and your bike will last a very, very long time.

Keep in mind however, that the stock radiator cap is designed to blow BEFORE damage occurs to the hoses or engine. Lost coolant is much cheaper than busted hoses or engine damage. But once again, my bike has never overheated since it is properly jetted and not left to sit and idle.


2000 XR650 uncorked, dual sport kit.

There you go! Proof in the pudding.

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