Power valve
 

Hi all, in my quest to get the ec250 running right. a mate said is the power valve sticking. Can I ask what this feels like and have any of you guys had this happen.

So far I have tried. 38 pilot,170 main, n1ed needle #3
42 pilot, 178 main and N1ED needle #3, #2 and #1
38 pilot, 175 main and N1ED needle #2.

It tops out at 50mph and seems to cough and spluter. It idle but only just with the adjustment screw nearly spring bound in.

It is running std sprockets 14, 48.
The starts first kick and reeds are new.

Which year?
Which carb?
Which reeds?

How fresh is the engine?
Have you physically checked the powervalve operation (engine running, pv cover off)?

It is a 1999 ec250
keihin pwk38
Standard reeds

No I have never taken the covers off while it's running

if you take off the rhs power valve cover, you can see if the actuator arm moves with the speed of the engine. It will make quite a noise, but it isn't dangerous.

Is this the Idle adjustment screw? Or the pilot air screw?

If the Idle Adjustment screw is all the way in. You have raised
the slide so high the pilot circuit won't be getting enough venturi
effect to pull fuel from the bowl.
That should not effect the High RPM running of the motor though.

I have had the power valve stick open when I kick the start the
bike a couple times. It makes a awful sound from the exhaust when
the bike idles down from the initial high rev from starting. Most
of the time the valve closes and goes back to normal.

Did you say the bike coughs and sputters at high RPM in every gear
of just in top gear trying to pass 50MPH?

To get the powervalve cover off, you will likely have to remove the
expansion chamber first to remove the cover, then reinstall the pipe
to test run.
Hope you get this figured out. My EC250 is a sweet bike to ride.

The N1EF needle that comes stock does not work well. Maybe the N1ED is not much better. Try a NEDW needle as mentioned in the jetting topic.

http://www.gasgasrider.org/forum/sho...t=2162&page=29

Considering that the bike is now 20 years old, the needle jet (brass part that the needle runs in) may be worn.

A stuck power valve changes the exhaust note to a higher pitch and the engine feels like it has less low end power.

I really like the ec250 like just starting to get a little frustrating.
The idle screw is the one almost spring bound. I tried winding it out and it doesn't start.
There is no strange sound and low down it is really powerful and Torquay.
It splutters in all gears. But it feels the same top end weather I have the 170, 175, 178 main jet in there is no real difference at all.
I have let someone else have ago to see what they think. He normally rides ktm.
He said it has alot of power low down but something is deffinately wrong with top end but couldn't say what! I don't know if that's was better cause someone thought there was something wrong or worse cause he didn't know what it was either

If you have something else to borrow from new coil, plug cap and sparkplug no matter how old, can find top end break down if you're lucky.

Also test going up a long hill. If it gets worse look for fuel filter and or kink in fuel line (caught me out. . . Again. . . not long ago, swine) and adjust float level, see sticky thread in carb section, also check tank bent.

I have ordered a new needle which I will try. I have tried new plug but not coil
I have replaced fuel line and filter as well