85 250R Overheating Causes

[Flyingw]

Guys,

when I built Whiskey Bent back in 09, it had a problem of overheating on slow moving high rev trails. When I got it up to open ground and got air moving through the radiators, it would cool down. Stock radiators and rebuilt water pump.

I refreshed it a couple years ago and sold it. I just found out it still has the overheating problem but now it does it on open ground. When I refreshed it, I put oversized radiators on it and rebuilt the water pump again.

My question is, what can cause the motor to overheat? I know the head is not obstructed nor are the water jackets in the cylinder. I'm at a loss as to what can be causing it to overheat.

[Flyingw]

I also know the pipe does have a good seal at the head. Perhaps the main jet is too lean?

[Flyingw]

Its running a Woods type 6 pipe

[Flyingw]

This is Whiskey Bent

[El Camexican]

Have you done a leak down on it? I don't know your cooling system first hand, but some require the non-cap side to be bled. If it's jetting it is more likely your pilot or needle is lean unless your riding pined out most of the time.

[atc007]

What head gasket? It doesn't take much to throw things off. Knowing how impeccable your work is, this is tougher. I'm sure you cleaned the rads thoroughly,what did you use? You are SURE they are open and flowing? My bet is a tad lean,not much, and slight restrictons inside the rads or head gasket
.

[El Camexican]

Do those trikes use a thermostate?

[82 250r]

You are describing my 250r perfectly on tight trails. Riding on trails in 1st or 2nd gear will overheat...just not enough airflow...i have to take breaks and let it cool down.
Define overheating on open ground. Boiling over after 10 min.? I have a temp guage on mine and it wont boil until somewhere above 245*.
I suspect there is nothing wrong with it.

[yaegerb]

What does your plug look like?

What makes you think it's running hot? Is your radiator puking?

[Flyingw]

Its had this problem from day one. I have done leak down tests and all passed. The plug was always a golden brown. I fitted it with an 86 TRX carb jetted stock and its always ran very well so I always left the jetting alone because of that. I sold it to Lisa Dugeon and they have it out at the dunes this weekend. The weather is hot and humid so that may have something to do with it.

[Flyingw]

and yes, the radiator is puking out the overflow bottle. To answer atc007, I've always run the metal head gasket.

[yaegerb]

Head gasket leak is my bet. I never had luck with the three piece metal gaskets unless you apply copper gasket. I stocked up on the OEM fiber gaskets. They seal 10x better.

[Flyingw]

its not the three piece gasket. Its a single CR250 metal gasket. I will have the owner install a stock fiber gasket and see how it does

[muthey]

what coolant is it running? I myself use strictly engine ice, just because all I ride is trails

[Flyingw]

nothing but ice.