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kirk garber

XR 650R Radiator Cap Question

5 posts in this topic

Ok, I know there has been a million questions about the XR 650R overheating but my question is about the higher pressure radiator caps ( 1.6 and 1.8 psi). Has anyone out there had any problems with their bikes as a result of using these higher pressure caps?

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Not that I've ever heard of. I've got the stock cap on mine, and I've never had an overheating problem. A properly uncorked and rejetted bike shouldn't have much trouble with overheating. The other possibility is the thermostat going bad, but I think it usually goes bad open rather than closed luckily.

All the cap does is raise the boiling point, which allows your motor to run hotter before the water boils. It doesn't really solve the problem. There are many people that install 120mm computer fans on one or both of the radiators. Put a switch on your handlebars and flip it on during slow going. A much better solution to the problem.

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I replaced my stock cap with a high pressure one as soon as I got my bike in 2003. I also still run the stock thermostat. My bike has never boiled over or had any cooling problems whatsoever, not even in 100+ degree weather.

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The big problem with overheating is on the tight trails where you can not get a lot of speed. Since I uncorked my bike, installed the SRC 1.6 radiator cap, and wrapped the header in ceramic fiber I have not had a problem. I got the ceramic fiber fro SRC also

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I use the 1.8 radiator cap and I run Evans coolant that contains no water. I've run real tight trails and monster sand hills and so far I have been fine. Go online and google Evans (npg+) coolant to find a distributor near you. It is well worth the money. You will need to drain the old coolant completely out and never use any other coolant product with the Evans coolant especially water.

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