Jetting question-air screw?

Been enjoying the jetting info, good thing for

the archives.

Anybody know what part of the throttle response the air screw affects?

Which one is it the carb? I've seen posts saying

they are running a 100. What is stock?

No problem finding the main, pilot and low speed

fuel screw.

My bike runs well with: 155 main, 48 pilot,

21/2 turns out, fourth from bottom on clip,

air box cover off, stock pipe (for now).

Idle is uneven with slight hesitation right

off idle. What do I need to do?

Thanks, Patrick

Patrick: Try raising the needle. Try the clip 4th down from the top.

Forgot the second part of your question was where the slow air jet is located. It is on the inlet end on the right side of the Main air jet. Stock is 90 and some have gone to 100.

The Pilot screw controls the slowest setting at idle. Your off idle response is more likly the needle position. And don't run the idle speed too slow.

If that does not work make sure the Accel pump is squirting.

Patrick: I need to correct the previous post. After working on my carb today I realised a couple of things. I was looking at my factory manual and it is wrong along with my terminoligy.

The SLOW AIR JET is a #60 and is marked (8)in the book and shown to the right side of the MAIN AIR JET which is a #200 marked (9) in the book.

The numbers are reversed and the (S.A.J.) is really to the left of the (M.A.J.). These are located on the inlet side of the carb but you have to remove the aluminum inlet manifold to find them. No need to even go there.

These are probably not what you were asking about anyway.

The AIR JET (A.J.) is the one that has been getting changed when the Yamaha YZ426 needles have been swapped into the Suzuki. It is located on the left side just above the fuel inlet inside the rubber hose. Suzuki is a #90 and 2001 Yamaha YZ426 stock jet is a #100. You probably do not need to change this to solve your off idle soft spot.

Just make shure the squirter is working and raise the needle to the 4th or 5th groove down from the top setting.

Then if you really want to get some mid range hit go to the 2001 Yamaha YZ426 stock needle. Part # 5JG-14916-JP-00. I got one by accident as I was trying to buy the optional EKP needle 5JG-14916-EP. The parts guy did not believe me because his fisch was wrong and changed the number (without telling me)when ordering.ARGGG! I had the carb out and realise he got me the wrong needle. I miked it up and saw i. It really does help the mid range hit A LOT.

I called and found a really helpful lady working the parts counter and she now has the correct needle and #100 A.J. ordered for me. She had to call Yamaha and they said yes the part # 5JG-14916-EP is a valid Yamaha part number for the optional needle and it works with the stock 2001 Yamaha yz426 #100 A.J.

If you try to order one of these get the jet with and make sure the parts person knows the number is a correct working #.

Previous posts on TT have discussed this and I am just trying to consolidate what I learned today.

All I can say for now is the stock Yamaha needle works with the stock Suzuki A.J. Just going around the block. Felt way stronger.

I will give it a good test tomorrow in the mountains.

Sorry to add to the confusion but had to report what I learned today.

Beep, Beep,Beep back it up there Victor. I am new to this also but have done extensive searches in the archives and jumped around this forum and otheres enough to respect your opinion. You are a very valueble resource. :) So now that I have sucked up please help me on this one.

I have read a lot about jetting kits and super tunning the DRZ E model. I plan on keeping the stock exhaust until someone makes a performance model without the noise but if I understand you correctly if I buy the Yamaha needle it will work better in my zuk than the stock one? I realy enjoy the bottom end and midrange of this bike but want to be able to have as much air time as possible with the front wheel with the least amount of effort :D:D:D This sounds like a easy upgrade with very little investment. Plus I want that mysterious edge on my buddies 2002 E :D

Rode the DRZ400E with the new 2001 stock YZ426 needle today. 41 miles mostly singletrack. 45/160 jets. I did not change the air screw settings as it idles same as before changing the needle. Set the clip in the middle as it is richer needle with faster taper than the drz. The off idle and mid range is improved. Mine never was bad but now if someone told me it was a kitted 430 I might believe them.

Milage was 30.4 mpg.

Still waiting for my EKP needle and 100 AJ to come in but the 2001 stock Yamaha OBEJ'P needle is an inprovement from the stock DRZ needle.

Again it is Yamaha P N 5JG-14916-JP-00.

I have not posted this on the jetting survey yet as it is not really fine tuned but the first try was startling at all throttle positions and all engine speeds and operaating conditions.

My muffler is stock with 1 3/8" stinger and the first baffle cut out 2 1/2 "and inner baffle drilled with 4- 3/8" holes. A stock muffler would work with maybe 45/150 jetting.

Some further info on the YZ needle. I compared the dimensions with the DR and found that overall length and shaft size is the same. Just the taper and length of taper is different. Th dr is about .8 degrees taper and the YZ is about 1 degree.

The YZ starts out at the tip smaller Diameter (.082") the DR (.086"). The yz taper is about 1.54" and the DR 1.41" long. The straight length is .107" Dia.on both so the yz has a shorter straight length. My dimensions are approximate as I was using old calipers and old eyes but close enough to explain why the low to mid kicks in earlier. The YZ taper starts about .13" earlier in the lift and tapers faster.

If you have the tools and patience you can modify the stock needle.

OH yes. my DRZ400E has a 48 pilot not a 45 as posted above.

It would be my guess that if you only changed the needle, as I did, you would see a great improvement in low to mid. if your jetting is in the ball park. If it acts rich go down on jetting not back to the DR needle. Or raise the clip. My Yz is in the middle and the Dr was in #4 groove from the top.

Suggest buying a clip when ordering a needle. They do not come with. If you have a spare you may never need it but if you do not. Well..

Will do the same Comparison when I get the EKP needle but I will bet the EKP option needle is much closer to the OBE standard 2001 YZ426 needle than either is to the DXP Suzuki needle.

Have a great holiday season.....Victor Venturo

Victor,

I run the EKP, clip #2, and also found it added alot in the middle. The stock needle is LEAN in the middle... no doubt. The EJP needdle you have is apparently only about a 1/2 clip richer than the EKP. I'm interested in your comparisons. The way I see it, carb tuning is an ongoing/ever-refining process with *alot* of trial and errror.

Victor,

Thanks for all the good info. I will try the YZ needle for sure. I found my rough idle problem was because I had capped an air jet that is external and hooked up to the coast diaphram thing. I took off the rubber cap and idle came up and smoothed out a bit. Starts well, seems to run OK for now. Much better than stock of course. I found the air et you reffered to (#60 stock) thanks. So far this is what I've got:

155 main, 48 pilot, needle clip one from bottom with stock needle, 21/2 turns out on fuel screw, stock air jet, air box lid off, stock muffler drilled 8 holes in first baffle plus exit pipe removed,spark arrestor retained of course. If this post is double spaced you can thank ATT, AOL,Bill Gates, Java, and whomever else is screwing around with the software, It Ain't Me!

Cheers, Patrick

CITY BIKE San Francisco

Ballistic: You The Man!

It was your post way back in August about the EKP needle that got me inspired to try one.

After getting my 2001 DRZ400E it did not seem to have the hit my 2k had so I finally made up my mind to go a little extra and took your lead and ordered the EKP needle. The parts guy got me the stock needle for the 426 instead of the optional EKP needle by accident. I do not know what the Keihin par # is but I will bet it is a EKR instead of the EKP I was going for. I used it anyway because it had a longer and more agressive taper like your post said the EKP had.

It may be the one I have is just as good for the DRZ because of The Suzukies less agressive valve timing than the YZ which the EKP option needle is designed for.

Ballistic you seem to be the first guy with all the best mods. When are you going to try advancing the Suzuki cams for the YZ like timing. I have been wondering about that since first reading about the WR guys doing it. Easy to do but I have no way right now to get a feel for valve to piston clearance. Any Ideas?

If you do it would be best to start a whole new post as this one is overdone from the original Question.

That is my plan when the EKP needle comes in and I can measure it and give it a test.

Have a great holiday. Hope you have a heated garage up north.....Victor

Victor: you touched on an important thing when you mentioed cam-timing. Cam-timing was one of the first things we checked on our production roadracers, I have seen bikes come out of the factory with timing opposite of what it should be. Checking cam-timing on DRZs for factory specs. at the first valve adjustmemt might be a good thing. Adjusting the cam-timing is a very cheap mod that gives results.

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