[Mick-e]

I did my first race of the season this weekend, and I had some over heating issues.
Last season I knew something was not right when at the end of a race I would have radiator water on the side of my engine, but this was the first time it got serious.
Here's the dish.
Standard OEM radiator running distilled water, and water wetter.
OEM overflow bottle.
The bottle vent is routed to the rear of my bike into the catch can, and that vents to atmosphere.
When the radiator would boil over it would fill the overflow bottle, and the catch can, then lubricate the underside of my bike.
After one instance of over heating I drained the system, and put straight distilled water in, ran the engine, then drained. It came out crystal clear.

So the question is why is it overheating?
One person had suggested the thermostat.
Is it possible to remove the thermostat altogether, yet keep the temp gauge?
This is a race bike and I want it to run full bore all the time anyway.

Another possibility is the water pump, but that is a simple mechanism, and if it was bad wouldn't I hear it?

OK what do you EX experts think?

 

[fog]

Your head is warped and will need to be flat lapped along with the cylinders. Nothing else will fix it.

FOG

 

[Mick-e]

It's a bone stock head so I'll throw it away and put a different one on there.
What does that mean flat lapping?
Why did the head do that?

 

[fog]

It's a bone stock head so I'll throw it away and put a different one on there.
What does that mean flat lapping?
Why did the head do that?

That won't help. the two pieces (head and Cylinders) need to be matched to each other.

Read my piece in the how to section on head lapping. http://www.ex-500.com/index.php/topic,735.0.html

FOG

 

[Mick-e]

Hey FOG,
Thanks for the info.
I read through the head lapping piece.
I have an old window pane that I could use as a flat surface.
Do you think that will work or should I try to get a piece of steel?

 

[fog]

I have used a table saw table, a solid cast Iron one. Go to Home depoo and by i 12' square piece of flooring marble or granite.

FOG

 

[cstem]

You may have checked this- but a faulty radiator cap can mimic other problems. A cap that does not hold pressure will allow a system to boil over just like a pot of water on the stove. It may not leak fluid fromthe cap which is why many discount it. Some auto parts stores or even your local MC shop can test it for you if they have the right adapter.

 

[fog]

The problem as I discribed it is very common and will overpresurize any rad cap evenone at100 psi (if you could find one)

FOG

 

[Mad Matt]

Pull the line running over to the overflow but leave the radiator cap in place. If you get coolant jetting out when running that's a dead giveaway that compressed air from the cylinders is sneaking into your water jacket. It will start to happen almost immediately before you are even warm because the pressure to open the cap does not come from the warming and expanding coolant but rather the high pressure air from compression in the cylinders. Eventually if things are allowed to go on long enough the heat of the combustion air will flash off your coolant in that small local area. But a small amount is huge because water flashing into steam expands at a ratio of 1600:1 and thus really cranks up the pressure.

If the cap alone was faulty, say running at atmospheric, you might overheat but not lose all of your coolant so quickly. (I assume that the water wetter is a type of glycol that raises the boiling point of your coolant.)

Oh and for a 100 psi cooling system you don't use a cap but a Watts pressure/temperature relief valve with a few modifications! ;D

 

[fog]

My point was ( besides being facetious) Was just That. The gas pressure from a cylinder could be as much as 2000 psi. More than enough to blow by any cap.
While this condition is call overheating,it is not just plain coolant loss. the overheating only comes when all the coolant is gone. I have seen cases where the coolant was blown over the side so fast there wasn't any to carry the cylinder head temp to the temp senson in the thermostat housing. The temp gage never reported a thing.

FOG

 

[Mick-e]

Pull the line running over to the overflow but leave the radiator cap in place. If you get coolant jetting out when running that's a dead giveaway that compressed air from the cylinders is sneaking into your water jacket. It will start to happen almost immediately before you are even warm because the pressure to open the cap does not come from the warming and expanding coolant but rather the high pressure air from compression in the cylinders. Eventually if things are allowed to go on long enough the heat of the combustion air will flash off your coolant in ;D

I'll try this quick test.
I have a piece of plate steel to do the repair if necessary, as it's looking like my main engine is still at the shop.