Countershaft Sprocket Seal go bye-bye

Anyone had there countershaft sprocket seal blow within 50 hours of use? Symptom: just rev the bike and watch the oil stream out from behind the seal retension plate!

I'm hoping its just the seal. If not, does this mean pressurized crankcase = something is blown = $$$?

The first and most common question is How tight do you run your chain?

Seems to me everytime this question is brought up, that is the answer.

If not, does this mean pressurized crankcase

Check to make sure air is coming out of the crankcase breather hose. It comes out of the valve cover and drains down along the left front frame rail just in front of the ignition cover... it's the one that usually leaves a few drips of oil in the back of your truck after riding. As long as that is clear and flowing then you don't have any pressure problem and you probably just picked up a little piece of debris that got stuck under the lip of the seal.

I ran the stock chain until the chain adjusters were about 3MM from full rear stop. Figured it was time to replace. Put on a new gold series O-ring chain and adjusted per factory manual checking for tight spots all the way around. Rode bike and blew seal. Checked the breather - it appears to be clear.

Maybe just a blown seal. I'll order part and replace.

I read an article in Dirt Rider on time where they raced the 400 in one of those long desert races and the only thing that failed was the contershaft seal. They figured a stick (in the desert?) must have punctured it or something.

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