Yamaha YZ426F Cooling Problem

I have a 2000 YZ426F that is having some cooling problems. On my last 3 rides (desert and trails in 80 - 100 deg F temps) I have seen coolant blow out of the overflow tube from the radiators. On each occassion approx. 25% of the coolant was forced out of the overflow tube. I was told to replace the 1.1 lb. rad. cap with a 1.6 lb rad cap. Has anyone else experienced anything similiar to this? Let me know...


I ride in hot weather also. Steep mountain trails going slow used to make it spew out.YZ's need a lot of air going across the rad. fins. Replace the cap AND drain out all the old rad. fluid and replace it with some Engine Ice. This cured my problem totally! It works. :thumbsup:

Replace the cap.

New radiator cap (you'll know it's good) Engine Ice coolant, a Boysen water pump impeller. Also, if you have a "cottage cheese" looking substance at your breather tube exit you probably have a head gasket issue. Anyway the above fixes lets my bored & stroked 426 run cool all day long. :thumbsup:

Use Engine Ice or Red Line Water Wetter, change the cap..and I can't recall if the your year had painted radiators. If so, have the paint stripped off.

Can some one post a link for the new cap on line? :thumbsup:

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