2002 XR650R anti freeze boiling out of overflow hose

2002 XR650R anti freeze boiling out of overflow hose (2hrs of riding in 1st/2nd gears).. Not sure if this is normal or if I should have a mech look at it?

Mount a fan, a 4" Spal puller is easy to fit on the rh radiator, to the tabs where the anti-smog stuff was.
The pig will get hot when used at slow speeds as the cooling system was designed for racing, so for high speeds.

It is also worth checking that the thermostat is working.
It is a common fault with the XR that the thermostat pin gets bent jamming the stat.
Mine was bent near fully open but it was still enough to restrict flow and cause boiling.

Take thermostat out

john316 wrote:2002 XR650R anti freeze boiling out of overflow hose (2hrs of riding in 1st/2nd gears).. Not sure if this is normal or if I should have a mech look at it?

How much fluid remains in the radiators after the 2 hour ride?

How fast in mph are you running at in 1st and 2nd gear?

Is the thermostat good?
Is the bike jetted properly?

Mauser wrote:Take thermostat out

As I've said, a very bad idea....

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Link - Radiator Fan

Link - SEARCHING TOPICS ON XR650R!!!!!

·        If you have experienced a boil-over situation with your coolant, consider switching to a radiator cap with a 1.6 or 1.8 rating (stock is 1.1). Honda doesn’t make a 1.8, but a KX8O cap is rated at 1.8 and will fit. The downside to going to a higher rating is it puts more pressure in the system, especially the hoses and fittings.  This increases their susceptibility to punctures and other damage. Remember, this liquid-cooled bike should not sit and idle for long periods without airflow through the radiators. Additionally, the system is designed to boil over and has a coolant catch to handle the escaping fluid.  This does not equal overheating, a common misconception.

·        The Baja race bikes use a 1.8 cap without the overflow tank and thermostat to save weight. They are able to get away with this by careful bike warm-up and racing with the bike wide open. These mods are not for the average rider!