If I have a full FMF fatty pipe V force4 reeds and no airbox just an air filter...

If I have a full FMF fatty pipe, V force4 reeds and no airbox just an air filter strapped to the back of my carburetor.

What main jet should I run???

Any help is appreciated!!!

  • Start with a 290

  • v4 are for a highly modded engine just sayin

  • I run a 300. No airbox lid, boyesen reeds

  • 300-310 main, 32.5 pilot , needle in middle clip.

    Up one size main if you premix at 32:1.

    Plug chop to confirm.

  • What do you mean by needle in the middle and the plug chop ?

  • The jet needle clip position.

    Plug chops are the correct way to arrive at the AFR.

    Before you make the plug chop run it is important that the float level is correct, the idle is set correctly and there are no air leaks in the system, otherwise the smoke ring may lie about the



    Warm up motor to operating temp.

    Fit new B8es plug, ride WOT through the gears and hold WOT in 5th or 6th gear for 10 seconds, or as long as you can safely.

    Switch off the motor and pull in the clutch, apply brakes to come to a stop quickly.

    Take the plug out and replace the old one for the ride home.

    Carefully cut the threaded end off the plug to expose the insulator.

    There should be a smoke ring of a cardboard or biscuit colour around the insulator.

    If it is non existant or a very light colour, you are lean and require a larger main jet.

    If it is a lot darker you are rich and may go down a size in main.

    I prefer to run a little on the darker side, I may loose a little power but it is worth it for the peace of mind that I won't need a rebuild so soon.

    You have to get up a reasonable speed so that you can get the motor to pull strongly.

    Then hold it Wide Open Throttle (WOT) for 10 secs or as long as you can.

    The idea is not to get speed but to make it pull strong at full throttle to get onto the main jet circuit. I find I can safely do it on a short run by applying the brakes some.

  • Ty Pendleton I run my clip in the middle on my needle jet. 32.5 pilot. 300 main. Terry Preston went over carb settings with me. Works perfect and hasn't ever ran this good

  • Will these two work ?? Terry Preston

  • If they are genuine Mikuni jets

  • As said , if they are genuine.....

  • Id run a dyno jet and mikuni pilot 35 mm pilot

  • R u bored over?

  • Stock pilot on blasters is a 32.5

  • In a 26 mm mikuni carb

  • The 35 may be too large unless your temps are sub zero.

    Where is the air screw set at.

  • I run a 35 w dyno jet but in bored

  • How many turns on the air screw

  • Dont quite remember

  • Buy from rocky Mountain. Genuine and really fast shipping. I believe they are cheaper as well