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  1. #1

    Help with Novi 42I carb jetting.

    Just picked up a set of Novi modified stock 787 carbs. The little paperwork i did get with them says they are 42I carbs. The carbs have never had fuel run through them, but have no ls or hs jets. Looking for some help on what to start with for jets for my 96xp. I am running a group k head, .045 squish, slightly ported cases, cylinders, motor currently turns almost 7100 with stock exhaust.

    Thanks


  2. #2
    96XPSS's Avatar
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    Quote Originally Posted by Piranha Performance View Post
    Just picked up a set of Novi modified stock 787 carbs. The little paperwork i did get with them says they are 42I carbs. The carbs have never had fuel run through them, but have no ls or hs jets. Looking for some help on what to start with for jets for my 96xp. I am running a group k head, .045 squish, slightly ported cases, cylinders, motor currently turns almost 7100 with stock exhaust.

    Thanks
    Post up a pic of those bad boys and let me see if they are like mine.

  3. #3
    Here ya go. Thanks








  4. #4
    "Tearing it up on the water" seadoobutch787's Avatar
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    On my 42's,

    I run 155 mains 80 pilots and 80 gram spring with my setup, i tried 167 mains and it was running to rich and the rpms were way down. My plugs are choco brown. I would ditch that stock fuel pump and get a high output remote one.

  5. #5
    Quote Originally Posted by seadoobutch787 View Post
    On my 42's,

    I run 155 mains 80 pilots and 80 gram spring with my setup, i tried 167 mains and it was running to rich and the rpms were way down. My plugs are choco brown. I would ditch that stock fuel pump and get a high output remote one.

    Do you have the same carbs? What exhaust are you running with that jetting?

  6. #6
    96XPSS's Avatar
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    Purty!

    I'd ask Tim @ Novi. 155 with a stock pipe sounds a bit rich. My guess would be 77.5 pilots, 150 mains, 2.0 and 80 gram springs on Proks or Fly's.

  7. #7
    "Tearing it up on the water" seadoobutch787's Avatar
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    My badd i run a spec 2 with a r&d head.

  8. #8
    Quote Originally Posted by 96XPSS View Post
    Purty!

    I'd ask Tim @ Novi. 155 with a stock pipe sounds a bit rich. My guess would be 77.5 pilots, 150 mains, 2.0 and 80 gram springs on Proks or Fly's.
    Are these the ones you have? Also, diagram shows i will need to run a jet in the return line, any ideas on size? I will try to give tim a call sometime next week.

    Thanks

  9. #9
    96XPSS's Avatar
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    Quote Originally Posted by Piranha Performance View Post
    Are these the ones you have? Also, diagram shows i will need to run a jet in the return line, any ideas on size? I will try to give tim a call sometime next week.

    Thanks
    Yes, they are exactly like mine. Glad you mentioned the jet. You need to drill the restrictor orifice cast in the return of the rear carb and install a jet in the "Y" of the fuel return line. I think mine has a 60 jet, but I will confirm this for you. I didn't agree wth the way Tim used a 30 jet in the front carb. This jet clogged all the time, and didn't keep the fuel pressures balanced between the two carbs. My way does. The front carb restrictor is in the fuel pump block, so when you eliminate it, the restrictor is eliminated too.

    It may be Monday, as I have a full day today and am going out of town.

  10. #10
    Quote Originally Posted by 96XPSS View Post
    Yes, they are exactly like mine. Glad you mentioned the jet. You need to drill the restrictor orifice cast in the return of the rear carb and install a jet in the "Y" of the fuel return line. I think mine has a 60 jet, but I will confirm this for you. I didn't agree wth the way Tim used a 30 jet in the front carb. This jet clogged all the time, and didn't keep the fuel pressures balanced between the two carbs. My way does. The front carb restrictor is in the fuel pump block, so when you eliminate it, the restrictor is eliminated too.

    It may be Monday, as I have a full day today and am going out of town.
    Thanks alot. No rush, appreciate the help with these. Mine have a fuel pump block on them. Should i run a remote pump with these?

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