Jetting question to JD - again !!


As per my posts last week, I've just put the bike back together with your 'base-line' suggestions. Namely;

EKN Needle #4

Main Jet #175

Pilot Jet #45

Pilot Air Jet #100

Pilot Screw @ 1.0 turn out

The airbox cover is removed, and the bike is YZ-timed (its a '99 WR with the FCR carb)

So, the results: terrible !!!

1. Starts OK, and ticks-over really sweet

2. 1/8 to 1/4 throttle, missing and banging

3. 1/4 to 1/2 throttle, really struggles to pick-up

4. Full throttle, really strong

So, what do you suggest I change first? Would I be right to guess that the bike is too rich low-down, and too lean in the middle?

Your valued help and advice would be most appreciated. That includes all you guys who have some thoughts.

Look forward to hearing from you.

Missing and banging?

Sounds extremely bad.

Try moving the needle to #3 and recheck the needle code stamped on it. Should be OBEKN. Is there anything else you changed?

Decrease the main to a #170 also, maybe unrelated but a good idea.


Should he be running the 65 start jet to go with the 100PAJ? Maybe lean also in the pilot jet???? I'm running a 50PJ in my bike?


What pipe are you running? Does the euro bike come with the octopuss? Have you tried opening the fuel screw?



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, YZ Tank and IMS seat, YZ number plate, odo removed, de-octopussed (Thanks Clark) EKP #4, 50PJ, 175MJ, 100PAJ and 65 SJ at 500-1000' Thanks James Dean!

The start jet is for choke operation, should not make a difference after the choke is off.

The 48 pilot jet may be better at 1 turn out, good point.

Brett, turn out the pilot screw to 2 turns with your #45 pilot jet and retest (1 3/4- 2 1/4 range).

I am suggesting things all over the map here (pilot/screw/clip/main), but they are going in the direction of where most bikes end up.

[This message has been edited by James Dean (edited September 22, 2001).]


What pipe are you running?

Thanks guys, I'll give some of these a try today and report back.

I'm running a 'CRD Header and Pipe'. Its an enduro legal 93db pipe, but behaves pretty well.

I'll keep you all posted. Many thanks.

Bill, there's no Octopus

JD, its definately the OBEKN Needle. For today, I'll try the #168 main as its the closest to 170 that I have at hand.

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