'01 XC300 Power Valve in backwards
 

Hi, Wondering if its possible to put the power valve in backwards. I just did a top end rebuild and bike runs ok on the bottom and mid but chokes out from 5/8 to full throttle. I took the pipe off and the power valve cover linkage side off. It was all hooked up and works but then I realized that its wide open with the bike not running. If I manual rotate linkage it closes and when I let go of it the power valve springs open. I would have thought the none running position would be closed to increase the low end compression. Please help.

Thanks, Tim

Yes, the flapper can be put in upside down.
The arched part of the flapper shoud be facing the exhaust port.

Thanks for the help. So not only can the flapper be put in upside. This was not my case. The valve was actually full open at idle and fully restricted at full throttle. Opposite of what should occur. I'm not sure exactly how I did it wrong put once I took the pivot and the long pin the controls the movement out and put it back together it worked correctly. I think it had something to do with the linkage being rotated past the normal stop point or maybe I tightened the upper linkage arm when it wasn't keyed properly to the stop. For now on I will verify its working properly anytime I disconnect the linkage.

Note: Any time I use the term linkage I'm only referring to the top end linkage as I never took the side cover off to see the lower linkage.

I also seem to have this same problem and can't work out why!
The flapper gas a step at the bottom which I have facing the piston, does anybody know if this is correct?
I have looked at the pictures in other posts and when the flapper is as closed as it can be the half moon puts the actuating arm in the wrong position.
Am I missing something??

Thanks

The step should face up.

It is possible to install the flapper actuating pin on the "wrong side".
The flapper has an oval opening that the pin rides in.
When the side barrell valves rotate, the pin moves the flapper up and down. So, if the pin is towards the front of the oval opening, the action will be reversed.

I'm putting my 300 back together.
I thought I marked the power valve flapper but I cant see it now.
I read some bad experiences with ruining the engine if its in wrong.
The first post says 'arched faces exhaust port'.
I see that one side has concave and tapered cut. I am assuming this is the 'arched face'.
The second post says the 'step should face up'.
The step is one the other side of the flapper, the side opposite the concave arched side. But if that faces up then the arched faces away from the port.
I am confused and nervous.
There is a long slot on the side that the rod from the cams goes thru.
With the arches facing into the engine head, towards the exhaust port, the taper runs uphill from the end of the arch, that is the opposite end of the fixed pivot rod.
If I flip it so the step faces up then the slot runs downhill as you go towards the fixed pivot rod.

Which way is correct?

From the diagram of the pv it seems that the arched faces into the head, the slot goes uphill towards the pivot pin.

I'm going to work on the forks and hope someone can help me out.
I cant afford a blown engine.

Thanks

UPDATE.......................
I tried it both ways.
I think I was reading the posts wrong.
In the 'wrong' way the flapper hardly moves.
In the 'right' way it moves a lot.
The "step" side faces up as you look down the bore and the arched/concave side faces out towards the exhaust system.
I was thinking the arched faced into the engine but this is wrong.
So when its in the 'right' way, and open all the way up, the arched side gets hit by the exhaust gases.

I am looking for feedback still though.
Thanks

this thread will really benefit from some pictures ...

Bringing this post back up from the dead... before I document in my build thread, I want to be sure I've got this right. It doesn't seem to close very far. I think that I have the flapper oriented correctly.

Curved side is down, facing the exhaust port. The ridge is on the top, facing up toward the head. Is this as far as it is supposed to close or am I missing something.

https://www.youtube.com/watch?v=0vewPHrZ33U

Here's how I assembled it:

Long pin through the hole, lined up through the hole in the top of the flapper, and into the other side of the cylinder:
http://i71.photobucket.com/albums/i1...pstismyhnt.jpg

Slid in the valve with the rotating pivot point:
http://i71.photobucket.com/albums/i1...psllrvipch.jpg

Insert the other valve, with the short pin. I put the pin through the slotted hole in the flapper and into the hole on the other valve:
http://i71.photobucket.com/albums/i1...psk5mricnf.jpg

http://i71.photobucket.com/albums/i1...ps80o2txoz.jpg

http://i71.photobucket.com/albums/i1...psdmiam0h0.jpg

http://i71.photobucket.com/albums/i1...pspawcolcd.jpg

Take this with a grain of salt, but it works for me. I put the arched face of the flapper towards the piston. All this other talk of up down, in out, is confusing to me.

Yeah, confusing because there are 2 curved surfaces. Did you see the video? Should it be closing more than that?


The bottom is curved: I have that end facing the piston:
http://i71.photobucket.com/albums/i1...ps6qqg3g0l.jpg

The face opposite of the "step" is also curved and I have that facing down into the exhaust:
http://i71.photobucket.com/albums/i1...pso6mnrxjf.jpg