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2002 XR650 overheating

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My XR just started overheating and running mid 200's driving through town. Hadn't done it previous until today. Puked coolant out most of my commute. Jetting is spot on. Coolant is fresher like a year old. No other issues I can see, hear, or are obvious. Coolant is not pressurized like a block issue or head gasket. Just super heated. To me this says water pump. Am I off base or should I look at something else first that I am missing as obvious? Stumped otherwise :-/  Thanks in advance for any advice!

BB

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Are you sure it hadn't done that before? Mine always did until I installed bigger rads.

You might have a stuck thermostat.

If not then you might be starving the head out of oil, but it would make the rockers a bit loose every time you boil it or every 200miles, so you would have to adjust the valves already.

Try the thermostat first, it's on the left side where the 3 hoses unite, you will see if it's twisted and stuck. You can ride without it until a new one comes

Edited by MCVL

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 Coolant is not pressurized like a block issue or head gasket.

 

 

The cooling system is supposed to be pressurized when at operating temperature and will remain so an amount of time after the engine is shut off.

 

The radiator cap maintains a calibrated pressure and if the coolant is heated too much, the cap releases some pressure. The higher the pressure, the higher the boiling point of the coolant. At atmospheric pressure, the coolant would boil at approximately the boiling point of water, which wouldn't do much for cooling.

 

The XR650R is no different. Stock, it has a 1.1 Bar cap. There are higher pressure caps available, but your problem has been recent. You should have the cap tested because it could simply be worn out. Any competent automotive shop has a cooling system tester that can also test caps, the question is if they have the correct adapter to fit a small motorcycle cap. A motorcycle shop should have one too, but if they are more into throwing parts at something until it's fixed then charging the customer for missed throws they might not have one because the tester and adapters aren't cheap. A radiator cap is fairly inexpensive, so if they are going to charge you to test it, ask if they can sell you a new a new cap if the current one is defective that way they may not charge for the test because you will buy a cap.

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Onederer, I have temp sensor that has been accurate on my Trail Tech. It shows spot on the boil over right before it happens. So it is indeed the temp of the coolant operating as it should. Now the temp of the engine is a different story. Don't know that. I will check thermostat action in the kitchen on the stove on Sunday. 

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