Powervalve question

[KDXXXX]

Hi Guys, I have a similar problem as this guy - http://www.kdxrider.net/forums/viewtopi ... 77&t=16458

I have a clean carb, air filter, tank and fresh packing. I have started reducing the jet sizes and it seems there are a some minor improvements
(I will continue dropping until it matches the jetting guide specs)

So this weekend I decided to check if the power valve functioning correctly. I took off the header pipe and the cover where the LHT "paw" gear of the powervalve is located. I turned the powervalve by hand while I was looking into the exhaust port. The two valves next to the main exhaust port seems to rotate and open and close when turning the PV. The the valve at the top of the exhaust port moves but I'm not sure if it is opening and closing all the way.

When I turn the PV all the way, the exhaust valve lifts probably 5mm (3/16") and drops all the way when I release it.
Is this normal or should the exhaust valve move more?

After that I re-installed the header, started the bike, revved the bike and watched the PV gear turning all the way and back - So no problems there

I'm just wondering about the exhaust valve movement???

[KarlP]

That center valve movement sounds right.
It does not appear to move a whole lot when looking in the exhaust. With the head off and looking into the cylinder you can see how it moves the point where the exhaust stream can exit quite a bit, in relation to the total stroke of the piston.

[Flanker]

Have you tried tuning the needle? mine does that, and I suspect the needle is to high (it is in the middle, I believe thats third position from top) but I haven't bothered changing it because the problem goes away after about a quarter mile it comes back if the bike sits for about 10 minutes and I ride it again it used to take about 1 and a half mile to go away when my muffler needed to be repacked and I had dirty air filter. I am curious to know your needle position, and if changing it fixes it cuz I'm to lazy to try myself

[KDXXXX]

Latest spec of my carb is 45 PJ, 158 MJ, Needle in 2nd grove. Initially it was in the middle but I moved it to the 2nd clip which made it slightly better, I think.

I am going to install 42 PJ and 152 MJ over the weekend and play around with the needle and see what happens.

I will let you know what happens

[scheckaet]

then i'll tell you the exact same: follow the jetting guide. see sig.

[KDXXXX]

then i'll tell you the exact same: follow the jetting guide. see sig.

Did you read the rest of my post?

[Julien D]

I think the point is that throwing random jets at it and hoping for an improvement is the wrong way to go about it.