over heating

[ryan6055]

I have a 94 zx-9 that when i ride it over about 40-50 miles (hitting the poweband) it gets real hot and spews out radiator fluid and of course it goes all over my rear wheel. Any one have any ideas? Am i looking at a thermostat replacement?

[Xusia]

Has the Radiator ever been flushed? It might be corroded and need replacing.

[ryan6055]

yeah i flushed the piss out of it, reading on some forums that it could be as easy as a new radiator cap, it did sit for 3 years, so it could also be a head gasket. Not sure, not looking forward to anymore labor than a new cap though. Any other ideas or advice on things to look at would be awsome, im gonna start doing what i can over the next few days.

[JohnPaul]

if you recently flushed it, there still may be air in the system "vapor lock sorta" that needs to be burped out...and ya the radiator cap could very well be the culprit...imo

[rickster]

Air in the system and the rad. cap are both likely culprits. If the head gasket is bad a pressure test of the cooling system should reveal it. A few of the late 80's-early 90's Kawi's were known for overheating a bit, but it was usually during hot weather and slow speed operation.

[ryan6055]

Got the new radiator cap tonight, late night at work so will check it out tomorrow. Now when i "burp" the air out is that the same as a car. I just run it without a cap until it barely bubbles over? Still learning alot when it comes to bikes. And the cap did have a small tear in one of the seals, im praying this works. If not i will run down to one of the motorcycle shops and do a pressure test to double check the head gasket.

[rickster]

Sometimes the radiator cap isn't the highest point in the system; hence the use of a bleeder (or bleeders) screw to allow the air to escape. Take a very careful look at your system; if any part of it (cylinder head, thermostat housing, etc.) looks like it's higher than the radiator cap, there's probably an air bleed screw on it that needs to be loosened while you fill the system, until liquid runs out. Sounds like the new cap may fix it for you, though.