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My son has an '02 YZ85 that started overheating. The oil was smelling strange so I changed it. It still over heats after running it for about 15-20 minutes. Any suggestions are greatly appreciated.
Thanks
mgee

The oil in that bike only lubes the tranny, so it won't affect anything motor-wise.

Are the rads clean and clear of dirt?
Are the louvers in front of the rads melted or deformed and blocking airflow. They tend to warp over time and can block the rads. They do serve a function by directing the air through the rads instead of across the front of them.
Got enough coolant in it?
Have you changed the jetting recently? 2-strokes will run hotter if too lean or too rich.
Has the bore been oversized recently? Without re-jetting, it can run hotter after a bore-job. Sucks more air.... same amount of fuel... equals lean jetting.....

I'll check the reeds. It hasen't been bored. I'll let you know what I find. Thanks so much.
mgee

To throw my pennies worth in, it sounds to me very much like a radiator problem.

Take a look at the thermostat in the radiator. It might have failed, so that it stays closed, ergo always set for cold starting, but never allowing the full cooling potential.
This is a common enough problem, so do take a look if the reeds look ok.

So does anybody know if there is a site that shows you how toos. like a repair manual?
Thanks in advance
mgee

Pretty sure your YZ don't have a thermostat, so if the cooling system appears to check out, might be time to look at the waterpump housing and impeller. Also make sure you don't have an airlock in the system.

A manual is a necessity for any and every bike you own if you ever want to do more than put gas in it. For anybody. You can buy one online (google it) or order it from a dealer, but you should have one. Chock full of useful info.

BuzZz wrote:Pretty sure your YZ don't have a thermostat, so if the cooling system appears to check out, might be time to look at the waterpump housing and impeller. Also make sure you don't have an airlock in the system.

A manual is a necessity for any and every bike you own if you ever want to do more than put gas in it. For anybody. You can buy one online (google it) or order it from a dealer, but you should have one. Chock full of useful info.

You might be right BuzZz, I am not familiar enough with the YZ to be sure. But most cooling systems will have a thermostat, so as to avoid the situation where the engine can't reach proper operating temperature for a long time(wasting fuel on the longer needed choke periods).

Motocross bikes rarely have 'em, but the occasional model will. wasting fuel don't factor into the design of a pure race bike much.

It appears the overheating has been due to a burnig clutch? Possibly when I installed the new clutch cable it wasn't quite (fully engaged) and may have caused it to burn up the 2 outer friction plates?
mgee

What is your idea of overheating??...what symptoms? And I bet the oil smelled of bacon....AHHHH, wonderful burnt clutch smell.