Help please brains trust!!
Posted October 13, 2001 - 03:24 PM
This is what I have tried so far.(99 wr400, wr timing, Staintune exhaust with and without bung in, Twin Air filter, sea level)
1. 172 main, 48 pilot, 1.5 pilotscrew, dxm #4. I played with the needle with the best results at #7 but still hesitates slightly and used lots of fuel plus ran rich. At #1 it backfired alot and still hesitated. Pilot screw to 2 turns but no difference.
2. Went back to stock main 168, 48 pilot, 1.5 screw, needle at #4. Still the same problem.
Does anyone have any suggestions on what may be the problem and how I can rectify it?
Posted October 14, 2001 - 04:34 AM
I''m certainly no expert on jetting but, looking at your changes vs. results. Your changes need to be made on the jetting at 1/8 to 5/8's throttle and you only changed the Main jet (3/4 to full throttle).
Jetting is very throttle position specific.
I would think turning out the fuel screw and lowering the clip is what you might have done first. If you get the fuel screw out to 2.75 to 3.0 turns, you may want to consider going up one on the PJ.
Here is also a list of "D" needles from lean to rich:
DTM, DTP, DVN, DVP, DVR, not sure where your "DX" needle fits in.
You might also want to consider YZ timing. I waited for a couple of years. I really didn't want any more power for woods riding and after changing. I wished I would have done it sooner. I fell it softened the bottom a little, to make technical riding easier (for me). Yet has the power to loft the front any time.
Also not knowing your altitude and country or if you have the airbox lid off or on makes it harder to recommend jetting or suggest removing the octopuss.
We now return you to your regularly scheduled program
99 WR400f, YZ timed, MX-Tech suspension, Scotts steering damper, White Bros E-Series (12 discs), tapered header and a/f. Kouba T-handle for the fuel screw. Works Connection billet throttle tube and frame guards. Cycra Pro-Bend, triple clamp mount handguards. Thumper Racing rad guards, Renthal Jimmy Button highs, All YZ Modifications, de-octopussed (Thanks Clark) EKP #4, 50PJ, 175MJ, 100PAJ and 65 SJ at 500-1000' Thanks James Dean!
AMA, Happy Ramblers MXC (Dist #7), Tower City and Rausch Creek
Posted October 14, 2001 - 06:37 AM
i'm going to beg to differ.
i run the '99\WR also and from your introduction "G'day" i know where you live and at what altitude-i hope.
i have worked with the needle you've got and you were right, the needle is best on clip 7. i've had it at clip 8! by using washers. however your problems are at lower revs and centred around the pilot system.
a 48 PJ needs a 110-125PAJ to correct the 1/4 throttle mixture ratio, BUT that even mixture is TOO MUCH so you need to buy a 45 and 42 PJ and an adjustable PAJ called the Pilot Air Screw. as you come down on one you can balance it with the other. eventually you could go all the way to 38PJ.
i think the hesitation is the sheer richness of the mixture making a flame path all but impossible.
you can discover more by looking at the thread "jetting Q's" which is still a current topic.
[This message has been edited by Taffy (edited October 14, 2001).]
Posted October 14, 2001 - 05:47 PM
I have not had the chance to try the smaller PJ yet for the hesitation problem.
Posted October 14, 2001 - 10:21 PM
i had this sensation on my first dyas testing in the spring. unfortunately i moved on to another project at the time and my notes weren't as copious then as they are now.
i did the test to get snap wheelies and not as the ultimate running guide.
if i remember i dropped the needle a clip and lowerd the main jet one.
i moved on to the EKP needle and it was all forgotten.
Posted October 15, 2001 - 02:12 PM
Is this really a problem or am I just too heavy handed with the throttle? Does anyone else have a similar effect when they crack the throttle wide open from low revs?
Posted October 24, 2001 - 02:19 AM
P.S. EKN is the next job.
Posted October 24, 2001 - 12:43 PM
At steady 1/4 throttle your bike still might be a little rich in #6, but snapping wheelies would be better than going to #5.
EKN#3 or #4 will add that back and more.