1. Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

Jumping up to a 134 size main jet?

Discussion in 'XJ Modifications' started by bluethunder91, Mar 29, 2020.

  1. bluethunder91

    bluethunder91 New Member

    Messages:
    12
    Likes Received:
    2
    Trophy Points:
    3
    Location:
    Eastpointe, Michigan
    Hey everyone, first time posting here. I have an 85 XJ700 Maxim that I'm in the process of completely redoing. It's been a long project, but I'll post the final outcome in another thread.

    Anyway, last summer I gave the carbs a stage 3 jet kit which gave me a 112 main jet. I believe it was a 107 that came out of it originally. A buddy of mine gave me a set of 134 main jets from his old bike, and they will fit my carbs. My question is, is this too big of a jump? I'm not super familiar with carb tuning, as I had a lot of trouble with it last year, but I feel better about my ability now. Has anyone here ever done a jump like this? What is usually involved? (different pilot sizes? air screw adjustment? etc.)

    I am currently using a 4-into-2 exhaust with high flow baffles, and pod filters with velocity stacks.
     
  2. Chitwood

    Chitwood Well-Known Member

    Messages:
    866
    Likes Received:
    374
    Trophy Points:
    63
    Location:
    Fort Atkinson, Wisconsin
    Best advice anyone has ever given me and I have tried to adhere to myself best as I could, get it running properly with as much stock everything as possible. Then as you make changes in components and tuning you have a baseline to reference. To me that sounds like way too much of a jump in jet size. I went from 40 to 42 on the pilots in my 650 and it made a huge difference.
     
    k-moe likes this.
  3. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    the stage 3 kits are supposed to be what you need based on info you gave the kit company.

    what bike are we talking about?

    the bigger the jets the less mpg you get. you want to tune your bike for mpg and quickness/speed.

    at some point you lose mpg without gaining much performance increase
     
  4. bluethunder91

    bluethunder91 New Member

    Messages:
    12
    Likes Received:
    2
    Trophy Points:
    3
    Location:
    Eastpointe, Michigan
    My bike is a 85 xj700N Maxim. I got quite a bit of performance increase after the stage 3 install. I was just curious if a bigger jump in main jet would yield more power effectively. Like I said, I got the jets for free so it's just curiosity while I have the bike apart.
     
  5. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,613
    Likes Received:
    6,703
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    Power happens when the mixture is correct for as complete a burn as possible. Bigger jets do not automatically mean more power (in fact it can quite often mean less).
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    getting an air box to replace pods may be the answer to improved performance
     
  7. bluethunder91

    bluethunder91 New Member

    Messages:
    12
    Likes Received:
    2
    Trophy Points:
    3
    Location:
    Eastpointe, Michigan
    Understood. Do you think I will have to modify the airbox at all? (Drilling holes, etc..) I have 4 pod filters with velocity stacks. When I was having tuning issues last year, the stacks corrected my full throttle range.

    Other mods are a 4-2 exhaust with high flow baffles.
     

Share This Page