jetting information overload !
Posted July 21, 2002 - 09:28 PM
I have a 01 WR 426 Candian with a YZ muffler,no lid.
3 turns out PS
I have some sputtering under light throttle at mid and up RPM's.I get rid of most of the sputtering if I move to #2 but the popping on deceration increases.Also this seams alot leaner than stock when shouldn't I need more fuel?This setting is pretty much stock except for the fuel screw and it's seems the best compromise without changing parts(tried the 170 MJ with different needle positions and fuel screw adjustments)
It's not horrible the way it is.It runs a hell of a lot better than stock.I'm still running the factory plug and it doesn't stall if I wick the throttle too fast.Should I go to a different PJ and try different needles ?It seems I need to be leaner to get rid of the light throttle sputter but richer to get rid of the popping.I'm just confused so any help would be appretiated.
P.S.I live faily close to sea level and I can't find any leaks in the exhaust or intake.
Posted July 21, 2002 - 02:55 PM
Posted July 22, 2002 - 07:22 AM
Posted July 22, 2002 - 06:51 PM
So it sounds like you're lean on needle and trying to compensate with pilot. What size pilot air jet did you have? You may also be successful with "EMN" type needle which requires smaller MFJ but I'm not sure how the straight portion would compare to a "DQQ"...
Posted July 22, 2002 - 09:06 PM
This is close to a DVP#4-5 which helps with the lean 0-1/8 and the needle clip can stay at 2-3 to help the slightly higher range sputter richness. (Second letter just shifts the clip position)
Last letter N is only slightly richer 0-1/4 throttle than the last letter P, then Q, then R is gets to be too lean.
When we start talking about Exx needles, this changes the taper of the needle to make it steeper than Dxx. The pointed end becomes smaller. It adds fuel (richens) at mid-upper throttle and can add too much on top unless the main jet is downsized.
Posted July 23, 2002 - 04:41 PM
THe DQP is shown as an option so I will try that soon.I think I'm sort of getting a handle on it maybe,kind of.I'll guess I'll keep studying these posts.
[ July 23, 2002: Message edited by: XC800.X ]
Posted July 23, 2002 - 10:25 PM
[ July 24, 2002: Message edited by: dominator426 ]
Posted July 24, 2002 - 08:20 PM
You could be right, the adjustment to DQP was meant to be significant. The last letters commonly used with Dxx needles are- M, N, P, Q, R, S. As you can see xxP and xxQ are in the middle. Considering the fuel screw is out at 3 turns, this may help reduce that and the popping on deceleration.
The first WR400's and most KTM's use DTM. The first YZ400's and the leaner KTM "-G" California models use DVR. The D-P will fall in the middle.
What I also see here is most bikes with a DQ- needle need a leaner clip position #2 or #3.
DQ-#3 = DT-#4.5 = DV-#5.5
Jetting is trial and error with a little experience and common sense thrown in. We'll have to see where Shawn ends up at.