Jetting or power valve??

[swazi_matt]

I have just done a top and bottom rebuild of my bike as well as a bunch of other maintenance

I finally got it all buttoned up and took it for a run in ride. It runs fine low down but when it would normally go into power band it starts spluttering and never kicks in - previously it would splutter a bit just before going into power band if the bike was cold after a long slow downhill for example

The guys that did the bottom end for me mostly work on ktms and commented that they had battled a bit working out the power valve mechanism and when I reassembled it ( they only had the bottom) the powervalve seemed to have a bit more preload than I remember

I did not change any jetting and used the same thickness base gasket so I am inclined to think that it is not jetting but before I open the powervalve up I thought I would ask here

 

[Jakobi]

Pull the lhs powervalve cover off the bike and watch to see if it's opening with rpm while running on the stand.

Your description sounds like the PV isn't opening to me.. but if you thought it could be jetting you could make sure the main hasn't fallen out. I'm guessing its mechanical.

 

[swazi_matt]

I did change one of the reed petals and flipped one over (local GG agent could only supply one petal)

I will take the RHS pv cover off tomorrow and see if it is opening when I rev it. The more I think about it I am inclined to think it is jetting, bike is great below about half throttle. don't know how, all I did with the carb was clean the jets (pilot didn't seem to be fully seated) unless the new conrod has changed the jetting??

 

[swazi_matt]

Thanks Jake will check it tomorrow
LHS will be a lot easier to take off. Is it possible to assemble the pv incorrectly? Ie have the cutouts in the wrong place?

 

[gasgasman]

There may be too much tension on the p/v actuator, keeping it from opening.

Usually, you exhaust would have a raspy-backfiring sound when the p/v is not opening.

 

[swazi_matt]

OK so i re-adjusted the power valve slack and checked that all the balls were still there - quite a force they need to excert to get full opening of the powervalve

And it did go into power band however there was still a bit of a splutter before the powerband kicks in (about 14 throttle mark), less so once the bike has been ridden on the pipe for a bit, so i reduced the pilot down to a 40 from 42. Having had a look at the top of my old piston i am convinced it was running rich in this area (low rpm - which is where i tend to spend most of my riding)

Main is a 170 and it looked fine when i checked it after a section of WOT

There is still a splutter at the same places (also only when the engine is warm - not hot - eg after a long slow section of chugging along or long down hills) and the research i did indicates that this has to do with the needle diameter. I currently have the NEDJ on the second clip so what would be the correct needle to move to assuming i would need to go slightly leaner (@jakobi)

 

[swazi_matt]

Ok from my research it looks like i would need to get a NEDK needle to lean out the diameter portion of the jetting

... or maybe i should try a 38 pilot

.... or maybe drop the needle down a clip ????

..... or maybe a 7 spark plug??

a bit more research and it may be a weather issue, sounds similar to this post
http://www.gasgasrider.org/forum/showpost.php?p=75674&postcount=24