I recently put a new topend in my 2011 300. I installed the #2 or b piston. The bike runs great but I have encountered an odd problem. Every once in a while (usually while hitting whoops) the bike will act funny. It takes on a really high exhaust note and loses power. When you hit another whoop or bump it returns to normal. At first I thought it was the silencer getting obstructed but I ruled that out. I am pretty sure the powervalve is getting stuck open. I checked the powervalve operation and it opens and closes smoothly. I looked in the exhaust port and noticed that the piston has a polished triangle shape on the front of it. It is about a half inch below the rings and matches the shape ov the powervalve flapper. I am pretty sure the flapper has been contacting the piston. Luckily it has not cuased any damage and has not snagged a ring. I am guessing this may be what is causing the powervalve to stick open. How do I clearance the flapper to make sure it dose not contact the piston. I am guessing that the #2 piston is just enough larger to cause this as with the stock piston this was not a problem.
powervalve clearance
- Thread starter jeffs2200
- Start date
GMP
Active member
There is no way that should happen if all is well. The piston size difference is miniscule at .01mm and have no influence on the PV flap. If the flap entered the bore it would hit the rings first. You may be seeing some normal wear of the moly coating along the exhaust port edge. The PV may be hanging but I would say they are unrelated. Did you have the PV apart and clean it? When the PV is full open, is the rod touching the edge of the cases as it passes through to the cylinder possibly sticking? Sounds like its sticking open not closed
Ok, good to know. I agree it seems to be sticking open. I did not take it apart and clean it. It looked pretty good and moves freely. I will check to see if the rod is rubbing against the case. I wonder if the power valve cover could be contacting the nut on the arm. The gasket is kind of jacked up. I am sure it is normal piston wear but I did not remember seeing it before. I will go ahead and clean the pv good while I am in there.
Jakobi
Super Moderator
I've had the powervalve gum and stick before. If you drop the actuator arm off the plate and remove the stop bolt you should be able to roll the valve through 360 degress of motion both ways without any binding. I found mine would jag as i would take it backwards sometimes. I think it was carbon buildup on the drum where it sits in the cylinder. A clean up and fresh bearings and its running like a champ!
http://www.gasgasons.com/index.php?site=static&staticID=133
http://www.gasgasons.com/index.php?site=static&staticID=133
Braaaaap! Wrong answer.
Lookey here........
http://translate.google.com/translate?hl=en&ie=UTF8&u=http://www.gasgasons.com/index.php%3Fsite%3Dstatic%26staticID%3D133
Jakobi
Super Moderator
We're blokes! Just look at the pictures 
But just incase if you wanted to know what they were saying, heres an improved link!
http://translate.google.com/transla...gasons.com/index.php?site=static&staticID=133
Cheers
But just incase if you wanted to know what they were saying, heres an improved link! http://translate.google.com/transla...gasons.com/index.php?site=static&staticID=133
Cheers
(F5)
Gold Level Site Supporter
Jake is Australian, its debatable if his native tongue is even a close approximation of english. . . . .(now where's the emocon for taking a step back avoiding a round house??)
