Blown piston, Power valve

[Tommy]

Hey, so i have now blown two pistons in just under a week, ad figured out that the right powervalve was hitting the piston.
So now i wondering, is there any possibility to adjust my power valve from not closing to 100%?
And btw Gasgas 125 2006,
Thank you!

 

[Elvis74]

There was s no adjustment for the PV.
When the PV goes too far into the cylinder,my our must grind it to the right dimension. It should be about 0,5mm behind the cylinder wall.


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[Zman]

I hear there were some aluminum power valves that were weaker. Pull the assembly apart and check all the parts closely. The Yamaha 125 power valves cross over. New ones are about 100 buck each and GG versions are about 130ish if you can find them.. There were two or three GG versions and i hear the steel versions were the strongest. Chech ebay for similar versions. Eric Gorr at Forward Motion set me up with some good Yamaha replacement parts.