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  #1  
Old 07-22-2004, 09:53 PM
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Default still losing coolant

     

I recently just changed my water pump gasket thinking that my solve my problem. problem is when i hit top of 4th and 5th, coolant comes out of the overflow, not a little, a lot. every tank full of gas i am putting 8oz of coolant in the bike. I have checked the coolant system over. flushed it out, and put the Ice antifreeze in it. What else should i check for??
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Old 07-23-2004, 08:42 AM
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Default Re: still losing coolant

Sounds like head gasket leak to me. The engine is pressurizing the cooling system at high loads, pushing out the coolant.
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Old 07-23-2004, 09:11 AM
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Default Re: still losing coolant

If it is a head gasket you would be able to tell it was leaking around the head unless it was going right into the motor. You say it comes out of the overflow one the radiator, by the cap?
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Old 07-23-2004, 09:14 AM
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Default Re: still losing coolant

The cap on the radiator is built to release pressure if it gets to high. I think I remember someone saying that other bike companies like say kawasaki or something makes there caps release at a hight pressure. Maybe on of those would fit. I dont' know if that is just masking a problem tho.
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Old 07-23-2004, 12:01 PM
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Default Re: still losing coolant

The head gasket can develop a leak that only goes to the coolant jacket and not to the exterior of the engine. If the cooling system is blowing out coolant, it's getting pressurized from somewhere. The only source of pressure inside that engine is the combustion chamber.
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Old 07-23-2004, 12:58 PM
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Default Re: still losing coolant

If it is your gasket it should overflow the moment your bike is started. If this is not the point your gasket is fine. It's also possible that the cap of your radiator is broken and leaking too soon. Another possibility is that your bike is getting hot. This often happens after a rebuild with a high pressure piston. If you just rebuild your engine I should look in this direction. running higher on gas or use some avgaz if this the problem. Please let us know.
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Old 07-23-2004, 02:07 PM
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Default Re: still losing coolant

All it all comes together for me. I never thought of the cylinder pressurizing the water jacket and cooling system.
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Old 07-23-2004, 02:14 PM
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Default Re: still losing coolant

Yes. it could pressurize it at idle, if it's a bad leak.

It could also take higher pressures to cause the gasket to leak. High pressures would generally require high gears and large throttle openings on a dirt bike. You can't maintain engine load in the lower gears, but once you get it wound up, you can load the motor pretty hard on a top speed run. This could be where the gasket starts to leak.

Or, like someone else said, you could simply have a bad pressure cap. That's the easiest fix. But since it's a two-stroke, a head gasket is a breeze to change as well, unlike on a thumper. Score one for the pinger crowd.
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Old 07-23-2004, 09:36 PM
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Default Re: still losing coolant

if it was the head gasket, would i lose compresion on the bike? because i tested it last week and the compresion was still 150 psi. did three tests and they were all consistent. i swapped my radiator caps with one of my friends radiator caps on his honda, and the result was the same. I think that i might have to try the head gastket. I don't beleive that the bike is running too hot becuase it has not blown up yet, and i don't feel any loss in power. not sure what else to look for. thanks for all the suggestions. I will definately let you guys know what was wrong when i get this mystery solved.
Berkley
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Old 07-26-2004, 07:24 AM
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Default Re: still losing coolant

Combustion pressure, particularly at maximum output, is significantly higher than the compression pressure you measure when testing the engine. It IS possible to have a leak such that it won't leak at low pressure levels, like when running at low loads or when doing a compression test, but will leak at high pressure levels such as when running high engine loads (large throttle openings in the higher gears).

The bottom line is this: your cooling system is getting pressurized beyond what it's designed for, causing the coolant to get pushed out of the system. Either your pressure cap is no good and is no longer holding pressure like it's supposed to do or your head gasket is leaking or both. I'd change the pressure cap first, since that's easy and cheap. If that doesn't do it, I'd pull the head and check both the head and the cylinder for flatness and any signs of a leak. Check the gasket as well. If both are flat, replace the gasket and see what happens.
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