Hello, My daughters boy friends srx had a center cylinder melt down, he shut it down before it had chance to seize, when he took it apart the power valve was sticking when he slid it back and forth toward cable housing, the other two valves work fine. Could the sticking valve have caused damage on that cylinder? Thanks for any replys.

I wouldnt think that a sticking valve would cause a cylinder meltdown... the valves open up at high RPM's to expel exhaust gases more efficiently. This allows for more high end power. I don't see any reason there would be no reason that I can see that would cause damage...just power loss.

What did the plugs look like that were on it? Did it overheat? or did something get in the cylinder and rake the side...?

Hi, whanker 57, I'll get back to you when I talk to son in law,I think plug was fine except for aluminum on electrode and the plug hadn't got to melt like solder. but was coming apart into little pieces and skirt was scored.

Has he checked the carb yet, to see if he's got something plugging/restricting his main jet causing a lean condition?

a sticking power valve will not cause a cylinder to burn down.
a sticking power valve will simply cause the motor to run less eficiently, burn more fuel and make less horsepower.
a plugged main jet in the carb will cause a cylinder to burn down, as will trying to run old non fresh fuel in a mod motor.
the centre cylinder usualy runs the hotest since it is in the middle. how does the piston wash look on the top of the piston that burned down? another way to tell if the jet was pluged and the motor ran lean is by looking at the color on the plug electrode.
dark plugs means a rich condition, light or white colored plugs means it was too lean and that caused the burndown. a perfectly jetted motor will have a golden brown to dark brown color on the bend of the electrode.