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  1. #1
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    premix ratio changes and carbs

    Ok i have been running my project ski in with a 32:1 premix ratio and want to lean that out to 40:1 since that seems to be what the general consesus is as far as premixing goes and i have now put 4 full tanks of fuel through it since it was built so i figure its run in as much as it will ( correct me if i am wrong)

    My question is, do i need to adjust the carbs if i change the premix ratio to compensate for the change in the fuel to oil ratio or do i leave them as is?

    FYI, its running very rich at the monent which i have verified by the piston wash and the plug readings i have done.


  2. #2
    Happily Self-Employed WFO's Avatar
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    Yes, you may have to make a minor mixture change, but I would tune the carbs with a tach, not by plug readings.

    Correct your fuel ratio and remove the F/As. Go to the water and set your lows, then make some wide open passes and start closing the highs 1/8 at a time while watching your rpms. When you dont gain anymore rpms, open an 1/8 and put the F/As back on.
    Last edited by WFO; 08-20-2008 at 06:29 PM.

  3. #3
    Moderator OsideBill's Avatar
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    What are your current carb settings?

  4. #4
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    bill

    i am not 100% sure on the jetting specs but i do know that they have 115 lows, 135 highs and a 95 return jet....i dont know the other specifics sorry or how many turns in or out the screws are.

    fuel presure is 2-3psi at low rpm and at high rpm its 5-6 psi.

    they are novi 48's

    thats all i know as i had someone help me with the build and he did the carb and head work for me, i was present but obviously did not pay close enough attention to what was going on as i was working on the hull at the time. this person also did the water tuning for me, he did tell me how many turns the screws were at but i neglected to document those facts.

  5. #5
    All hail the Chief! fullboogie's Avatar
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    Going from 32:1 to 40:1 will richen your mixture. I'd start by tuning towards a leaner mixture when you get it out on the water, especially since you are already running rich.

  6. #6
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    what if a pitch up first prop wise?

    I have a 14/22 in her atm but i have a shiny new 14/23 from imrpos waiting to go in, just aint goit around to it as i was testing other things first up...thats why i left it rich... i figured go up a pitch then tune get the carbs dialed in...

    does it make sense to do it that way?

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