Sticky power valve??

[moff747]

Hi, can the power valves on ec300 somtimes get stuck? I had a ride yesturday and somtimes I had no topend power, low down power was strong and consistant. I found that backing off the throttle and powering on again brought it back to life. It seemed to happen more after a period of low revs. Any ideas?

 

[PEB]

Sounds like you are a little rich on the bottom.

 

[moff747]

Ok.My mixture screw is 4 turns out, this was set by the previous owner. 4 turns seems a lot to me.

 

[JoshP]

4 turns out on the Air Screw?>????? That is way too much is sounds like and the past owner might have been using the air screw to compensate for a richly jetted bike or other issues. I would bring the air screw down to like 2 or
2 1/2 at most and you should see where your issue is. I had a bike sucking air through the case gasket and the bottom was awesome but felt really weird up top. Now on to the original question yes your power valve can get very nasty (Especially if running very lean it tends to get burnt onto the power valve making it sticky) and if it is not a jetting issue (which I would check first since it's easier than taking the top end apart.) then you can tackle the valve.

 

[moff747]

Thanks, I will try the screw at 2 1/2 and see how that is.

 

[iancp5]

If it's a mixture problem you'd expect it to be consistent especially if lean. If it's very rich on the bottom then you might be spooging up which will cause it to 4 stroke and splutter when you open it up after a period of low rev / low throttle running. But in my experience it's pretty obvious when that has happened. If it was because it's lean at the top it will still be lean even if you back off for a second and re open it up. You seem to be indicating an intermittent problem so I would certainly be suspicious of PV sticking so don't rule that out. I don't think an incorrect air screw would have much effect at large throttle openings.

You can do a rudimentary check on the PV by removing the right hand cover and moving it by hand to feel for stickiness and watching it with the engine running to see if it is moving smoothly. If you remove any of the little nuts and bolts be sure to block the hole into the crankcase - because that's where they're going if you fumble.

 

[Leon_gasgas]

Hi!

During my last ride on an MX track towards the end of the ride when I finally decided to use full power on 3rd to go uphill, the power came strong and the bike felt that it cleaned up (before this ride I did the 1 hr break in plus 3 hours total with moderated throttle openings in the woods and the ignition on rain mode). But, during the braking the sound changed (like higher frequency..) and definitely there was less bottom power and the bike couldn't take revs on 2nd after the turn. I backed off and very soon it worked ok again. During the next round I tried the same and the same things happened. Like the plug was dying or something.

When I stopped there was a lot of spooge on the exchaust and swingarm. I checked the plug and it was wet and black. I changed it with a BR8EG and the bike started first kick and it felt ok. Yesterday, doing a simple check up I found out that the clamp tighter of the airbox and carb was loose a bit so I fixed that. Could this cause the problem? Or, is it the powervalve sticking? Or, too much low-mid rev working after the break in and the oem plug could not last the full throttle? Jetting is OK for the temps now. Bike is an EC250 07. I hope was only the plug.

Thank you for any reply!

Leon

 

[iancp5]

Hi!

During my last ride on an MX track towards the end of the ride when I finally decided to use full power on 3rd to go uphill, the power came strong and the bike felt that it cleaned up (before this ride I did the 1 hr break in plus 3 hours total with moderated throttle openings in the woods and the ignition on rain mode). But, during the braking the sound changed (like higher frequency..) and definitely there was less bottom power and the bike couldn't take revs on 2nd after the turn. I backed off and very soon it worked ok again. During the next round I tried the same and the same things happened. Like the plug was dying or something.

When I stopped there was a lot of spooge on the exchaust and swingarm. I checked the plug and it was wet and black. I changed it with a BR8EG and the bike started first kick and it felt ok. Yesterday, doing a simple check up I found out that the clamp tighter of the airbox and carb was loose a bit so I fixed that. Could this cause the problem? Or, is it the powervalve sticking? Or, too much low-mid rev working after the break in and the oem plug could not last the full throttle? Jetting is OK for the temps now. Bike is an EC250 07. I hope was only the plug.

Thank you for any reply!

Leon

If it's 4 stroking and spluttering it may be just too rich on the bottom. But is it doing this? Do you know what I mean by 4 stroking and spluttering? An air leak at the airbox will make it run leaner not richer. Generally if it sounds clean it's either bang on the money or too lean. Being too rich will make it 4 stroke a lot but I can't describe what 4 stroking sounds like - I just know it when I hear it. Just to make it more complex a little 4 stroking on an almost closed throttle, on overun is ok but not much and I again I don't know how to describe or quantify that. In fact it's safer - the line between perfect and too lean is quite narrow so a little rich is preferable.

 

[moff747]

If it's a mixture problem you'd expect it to be consistent especially if lean. If it's very rich on the bottom then you might be spooging up which will cause it to 4 stroke and splutter when you open it up after a period of low rev / low throttle running. But in my experience it's pretty obvious when that has happened. If it was because it's lean at the top it will still be lean even if you back off for a second and re open it up. . . . . . . . . . .


I wont get a chance to have a play about untill the weekend, I will take a look under the cover and check the power valve opperation. Just out of curiosity, how is the power valve opened? I know it has a push rod connected to it, is it back pressure? I will look at the carb jetting too, I know the bike was set up in warmer weather. The plug was a light brown last check.

 

[Leon_gasgas]

Hi!

I found out what was causing this strange situation! Too small pilot jet for the temps now. I screwed in completely the air screw and the problem almost disappeared! 40 and 42 jets came with the kit so I will go straight to 42. Sorry to spam this thread but the problem seemed similar.

Thank you!

Leon