jetting questions.......again

Just bought that new Ti-powercore 4 and mega bomb header, my question is during my adjustments, I was unable to set my fuel mixture correctly

old set up: stock pipe (end reducer removed)

all free mods 170 mj, 48 pj , 04 needle set at 3 from the top and 1 3/4 fuel mixture ran good, no real bogs. riding area 0-3000

I was unable to reset my fuel mixture screw, with the rpm set allittle higher the screw turned all the way in and motor still running, (no stutter) as I turned it out around 3/4 to 1 turn seemed ok. (crisp) once I pasted that spot the idle fell off and hard to start. Changed needle to the JD kit blue #3 from the top same jetting as above. Does another one have any suggestions. or do I live with 3/4 to 1 turn out and hard to start??


You need to go to a 45 pilot jet if you can turn the fuel screw in all the way with no difference.

Why did you change the needle when you were setting the pilot circuit? I take it that you just got the JD jetting kit!

Correct on the JD kit, don't think I needed just added as potential fix. Defiantly can return if stock 04 needle works with a 45 pj. Was thinking of trying a 172 mj, but i"ll try the 45pj first. Just a little weird when my bike ran fine with a 170,48 and 1 3/4 fuel mixture. With a 45 pj do you think starting will be a concern?? thanks

I just put on a ti powercore as well.

Previous set up was 170 main, 45 pilot, fuel screw 1 3/4 out. stock muffler with the pea shooter thing removed, starting was pretty tough when it was cold out.

Going to try a 172 main, 48 pilot, and adjust fuel screw as needed.

Going riding tomorrow so I can try and report back tomorrow night as to what I end up running and liking. I'm riding dunes tomorrow so the elevation is 0.

I wouldn't go any fatter than a 170main and the 45pilot is too lean for lower elevations with warmer climates.. I seriously doubt that a leaner pilot jet is going to help you. Nine times out of ten the magic combo seems to be a 168/170 and a 48.

Tonight I'll try the 168 mj, and retune the fuel mixture screw.

Tuning directions:

1. Start motor, set idle a little higher than normial (let warm up 5-10 minutes)

2. Screw fuel mixtures screw down until engine sputters/dies

3. With engine running turn fuel mixture back out 1/4 turn at a time until engine rpm exceeds orginal set point.

4. Once engine sounds crisp leave it

I was thinking that 170/48 and 1 1/2 - 1 3/4 was needed with this pipe set up do to it flowing more air.... but engine dies or loses crispness when fuel mixture passes 1 1/2

if this is the wrong or right please advise..........thanks

You need to go to a 45 pilot jet if you can turn the fuel screw in all the way with no difference.

I need to correct myself from above because I tend to agree with Matty now, only because I had a similar problem with a Honda mini project I'm workin on, just like your bike the only way I could get it to run was to screw the air screw all the way in, like you I questioned that setting. I started to replace the pilot with leaner jets and the bike actually takes to the mixture screw now. So go ahead and try the 45 and see what happens. There's not a whole lot of difference between the 168 and 170, I would try your pilot first...

good luck, let us know what happens...


ok .... pj it is


ok .... pj it is


Just changed pj from 48 to 45, and keeping 170 mj...funny thing still unable to to have motor stumble when fuel mixture screw is completly closed. Nothing blocking fm closing

Current set up:

170 mj

45 pj

1 turn on mixture

blue needle on 3 from the top

maybe I shouldn't worry about !!!!

Where do you think it runs the best? This is ususlly your best setting!

Have you pulled the carb off and cleaned it yet?

If the bike still has starting problems, you could try palying around with starter jet sizes.

A few people here have changed theirs.

Your Problem sounds a little odd - something sounds amiss.

The pilot circuit and starter jet is essential for good starting and idle response.

I would recommend going back to the basics.

I would clean the carb (as Matty says + blow out the PAJ), put in a 48PJ, and change out the starter to 70 or 72 (check the data bases). Most WRs will run well on 168/170 Main Jet regardless, as previously pointed out.

I would also put in fresh fuel and plug.

If you have the JD try Blue 3 with that exhaust.

Check the fuel screw is correctly set, around 1.5 to 2 turns.

While at it, set the AP timing.

Be systematic and note all changes you make and ride the bike between changes.

I know this sounds a lot but from your reported problem, but you need to make sure everything is working properly first...

My .02 worth


Completed all the cleaning as one to go and matty sugested, fired her up with the following settings:

alt. 500 feet

170 mj

48 pj

blue needle set on 3 from top

1-1/2 out (rough idle, bog) on fuel mixture let idle than rode for five minutes or so, tried to adjust the fuel mixture in but, still wont sputter or die when set all the way in, best posistion was around 3/4-1 out. Did a plug ( new Plug) check looked a little lean. ( light brown ). Just wondering if I lower my needle to location 4, would that richen or change things ??? Who said jetting wasn't fun............

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now