valve repair

Cossack blown exhaust valve repair guide, Mark Guest AUS

3 thoughts on “valve repair

  1. JD

    Cordless drill… good idea Mark. I’ve always used my faithful little grinding stick and suction cap. I’m still using the same tub of valve grinding paste I bought 40 years ago, mind you don’t need much 🙂 Cheers.


    Forgot to photo – how to bed in this valve using a cordless drill. This works well…..

  3. JD

    The easiest way to bend a valve is to start up a cold motor and then fang it. An engine needs at least a few minutes (read 10-15 minutes) or several kilometers (read 10-15 km) just to reach operating temperature. Even then it’s not a good idea to fang your bike at full speeds, something WILL break…. The last thing you want is the valve head ripping off and smashing thru the piston, then your’e walking, or hitchhiking.

    A compression test will show up a low reading, The best test is the kero test. With the cylinder head removed and the combustion chamber facing upwards pout in some kerosene. If it pours straight thru it needs a new valve or a serious bit of cleaning and grinding. If the kero doesn;t begin to leak thru for 30 seconds your’e good to go.

    Whenever you fit a new moving part, it has to be run in all over again. Keep this in mind before you go for a fang.


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