Carb configuration - 2001 DRZ400S

[sgifford]

Hello,

I'm a new owner of a 2001 DRZ400S with 12,000 miles. I'd appreciate some feedback on configuring the carb for my location, and what I want from the bike. Here are the facts (the bike came from New York state.):

1. Mikuni carb

2. 3x3 mod done (previous owner)

3. Stock pipe and muffler, with end tip damaged and restrictor removed (previous owner)

4. Needle is 3rd clip from bottom
5. Main jet 132
6. Pilot jet is 25
7. Fuel screw 3.5 turns out

Observations:

1. Idle: Uneven idle. Sometimes revs up and down but doesn't die..

2. Acceleration: Pulls strong on full throttle. Very slight popping on decel. Going off throttle, takes a couple seconds for idle to drop.

3. At cruise,1/8 throttle, uneven power and surging.

I live in Phoenix. Elevation 1200 -6000 ft.

Summer temp range 80-115 degrees. 

I'm going to put an unmodified stock muffler on the bike. I don't like loud. Mostly off road use. No freeway time.

I'm trying to do this (update the bike) on a budget, so I'm hoping to just buy pilot and main jets, and adjust the needle clip position if needed. I appreciate any feedback.

Seldon

 

[bumtarder]

Do you know what jet kit brand and needle that you have?My guess is you have a old Dynojet 3109.001 stage 1 kit.You are actually at clip #4.Needle clip is always referenced from the top,flat end.

Edited May 24, 2020 by bumtarder

[sgifford]

I don't know. I'm pretty sure it's not the current kit. The pilot jet has a logo on it. Hopefully the uploaded pic will let you see it.

[sgifford]

Here's a pic of the extended fuel screw that was added by a p/o.

[bumtarder]

That is a Mikuni pilot and a Kientech extended fuel screw but it says nothing about which jet kit you have.

The 132 main jet does seem to give a hint that it's a Dynojet kit as it's a wierd sizing they used in their kits and really not compatible with genuine Mikuni jet sizes.Normally for stock exhaust a mikuni 140 main jet is used.If it pulls good you may want to leave it there for now.

The steady throttle surging could be rich on needle clip.You may try dropping the needle to clip 3 which will lean the tranisition from pilot to needle circuit and then retest.You also need to see if the idle reacts to the manipulation to the fuel screw after the motor is at full operating temp.If your idle speed is set too high it will cause a hanging idle because it'll be on the needle and not on the pilot where it should be.Fuel screw is usually 3-3.5 turns on the Mikuni.

Edited May 24, 2020 by bumtarder

[npm]

This worked well for me, try a Mikuni 140 mj, clip 3 from top, and drop your 25 pj back to the stock 22.5 with the aftermarket fuel screw., DJ stage 1 kit, 3x3 and stock exhaust. Kientec extended screw 2.5 turns out. I've run this combo from SL to 4000+ feet.

Edited May 25, 2020 by npm