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TPARSONS64

YZF450 08 stuck open exhaust valve

7 posts in this topic

My buddy has the bike listed above and had this problem. The bike has around 40 hrs on it and takes care of the bike. A mechanic told him to hit the valve and sure enough it closed shut. The mechanic said don't pressure wash the bike since the valve rusted and stuck open? What can rust causing the valve to stick open? Is this common, never heard of it before.

Thanks

TP

:ride:;):p

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The valve seats are cast iron, and if enough moisture gets in the exhaust system, either from over zealous and careless washing, or simply from a damp climate, AND you are not in the habit of turning the engine up against compression when you leave it sit for more than a day or so, rust can form on the seats. Rust is seldom cooperative enough to form in a nice uniform layer, so when the valve next closes, it can't create a complete seal. Bouncing the valve off the seat a few times by tapping on the lifter with the cam in the closed position normally clears up minor cases of this.

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The valve seats are cast iron, and if enough moisture gets in the exhaust system, either from over zealous and careless washing, or simply from a damp climate, AND you are not in the habit of turning the engine up against compression when you leave it sit for more than a day or so, rust can form on the seats. Rust is seldom cooperative enough to form in a nice uniform layer, so when the valve next closes, it can't create a complete seal. Bouncing the valve off the seat a few times by tapping on the lifter with the cam in the closed position normally clears up minor cases of this.

Ouch - best I remember to do this, living with 90%+ humidity here. Thanks for the tip :ride:

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you are not in the habit of turning the engine up against compression then you leave it sit for more than a day or so, rust can form on the seats. .

Can you give a quick lesson on how to do this, for dummies like me.

Thanks

Toby

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The compression stroke begins where you feel the "hard spot" as you turn the kick starter. Once you feel that sudden increase in resistance, both sets of valves are closed.

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