JamesDean, Taffy, Hick or whoever else.....
Posted August 13, 2002 - 09:57 PM
I cannot do the BK mod ('98 carb, right?) so it will all be jetting.
I wanted to start with:
158 Fuel Jet (currently have 172)
??? Air Jet (currently have 200)
38 Fuel Jet (currently have 45)
60 Air Jet (currently have 100)
I went down to the local shop, and all that they have is the 158 Main Fuel Jet and the 38 Pilot Fuel Jet; so it looks like I need to place a phone call into Sudco.
The only YZ needle that they (local shop) was the ODBV-Q needle. Is that what I need, or shall I ask for something else from Sudco?
Also, what air jet shall I ask for to correspond with the 160 main fuel jet?
Posted August 13, 2002 - 02:04 PM
Posted August 13, 2002 - 02:49 PM
You are right about the BK mod, can’t be done on a 98. I think taffy had some sort of AP mod, try the search but definitely take care of the accelerator pump.
I don’t think you need to mess with the maj until you see how it runs. For now leave the 200 maj. For needles try an EMN clip #5 or EMM clip #4.
James Dean: What symptoms will the bike give when it’s rich on top? Same way if it’s lean on top, what symptoms will the bike have?
[ August 13, 2002: Message edited by: tk421 ]
Posted August 13, 2002 - 03:00 PM
I’m a big fan of E taper needles in the 426, as is JD (KTM thumpers also come stock w/ Ds). Taffy used to run them in his 400 too, then he had some sort of epiphany and I thought he switched back to D needles.
But right there in Bill’s sig is an EMM.
What’s in the sig above looks fine to me. The 60 PAJ seems a little small for a 38 pilot, but if it works it works...
In my 426 I run a 40 and about 85 on the PAJ. It seems relative exhaust restriction makes the biggest difference here. With the stock 100 PAJ my bike pops like crazy on decel w/ a T4 or R series silencer. With the stocker it is still lean, but not as bad. I just went smaller until I had good trailing and neutral throttle and the popping went away also.
So while you’re on the phone w/ Sudco then make sure you order the adjustable Pilot Air Jet, also called an air screw. Two PNs, 021-230 & 021-235, one is the spring and one is the actual screw. One turn out equals a 100 PAJ, ¾ is an 85 I believe.
Click HERE for a good jetting guide, there is also a table that gives the full range of air screw settings and corresponding sizes.
If you want to do a BK-like mod to your slant FCR, just buy a wheel collar (for RC cars etc., I imagine) from a hobby shop.
Apparently you want the 3/32” size.
Click HERE for a TTalk post on this subject.
The idea is you slide this collar over the actuating rod and use the set screw to lock it into place on the rod at whatever distance from the carb body that gives the amount of pump operation that you want. It just acts as a stop on the pump mechanism, like the BK mod, but in a different way.
I’m not sure, but that EMM needle may appear on the 250F parts fiche...
Hope this helps.
Posted August 13, 2002 - 04:46 PM
Taffy's is easier than mine, but both work great.
Posted August 13, 2002 - 07:46 PM
Brandon, don't reduce the main by that much (158) unless you are using an EMM or EMN needle. The Exx needle interacts with the main to need a lower size. The Dxx needle will use a main jet in the range of 172-178. The 158 main jet may need a main air jet near 160 using EMM#4-5. A 165 main jet will likely work with a 200 main air jet and EMM#4.
tk421, if the bike is rich on top it will either sputter or just not rev out. It may seem like the rev limiter is cutting out too early when you try to scream it. When the bike is lean it will not pull with the authority of the next richer main, just revs less quickly.
Posted August 14, 2002 - 05:28 AM
Anything I can get to stack the deck in my favor, I will do!
Side note: Last weekend, I overheated my bike for the first time (was a very extreme hillclimb that was approximately 2.5 miles long with many switchbacks, logs, switchbacks, , ruts, switchbacks, rocks and did I mention switchbacks?, there just was no speed about it so there was also no airflow). Will this leaner jetting cause the bike to run at higher temperatures?
Thanks for all of your help Gentlemen! I will attempt to do you proud.
*Just got off the phone with Sudco, and I have an adjustable pilot screw on the way, as well as a EMM YZ needle. Couple that with the 160 main and 38 pilot jet that I got from the local yahoo, I should be ready to go. Right? *
[ August 14, 2002: Message edited by: BrandonW ]
Posted August 15, 2002 - 08:18 AM
I pulled that thing out of the connector last night, and I am throughly impressed!
This thing is just about where it needs to be.....
Smiling ear to ear,
Posted August 15, 2002 - 11:23 AM
The grey wire mod was the last mod I did but did not notice any performance gain. I did notice that the mid engine control improved but that was all. From what I’ve read here, the pre 02 WR’s seem to really benefit from the grey wire mod.
Glad to hear your where you want it… happy trails!
Thanks for the info on the lean/rich conditions up high. The maj is still confusing to me, still learning this jetting thing. It’s been 16 years since I’ve ridden, the IT175 I used to ride worked well. Barley new where the carb was let alone jetting it. Just put premix in and go!