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  1. #1
    Millertime44's Avatar
    Join Date
    Aug 2008

    750 ZXi Converted to pre mix - change carb jetting required?

    Last summer I finished a complete rebuild on my 96 ZXi 750 and as part of that, converted to pre-mix. I broke it in carefully but when I started pushing it harder I'm having issues keeping it running on the water. I have to have one hand on the choke while my other is pulling on the throttle so it won't lean out and die. Now that the season is (FINALLY) coming around here in Minnesota, I am about to pull it out of storage and get it ready for the year again. Was planning to try rejetting the carbs with a bigger main jet.

    1. Is it common to need to rejet after converting to pre-mix? Is the mixture affected enough via that change that it's par for the course, or do I have something else going on?

    2. If I'm still running a bit higher oil/fuel mix (e.g. ~35:1 or 40:1) would that cause me to lean out like this at WOT? Would running a straight 50:1 help (and would it be sufficient oil for a relatively new build)?

    3. I've read a couple places that the oil pumps normally don't fail, and that just replacing the hoses with new polyurethane is usually sufficient to fix the oil injection problem. Would making this change help alleviate my problem with no carb work required?

    Thanks for any help.

  2. #2
    You should follow mfg's recommended fuel/oil ratio which is 50:1.
    I've heard, if you use synthetic, even 100:1 works with no engine issue.
    Besides all that, you should make sure there is no intake leak causing too lean problem. I would not change factory jetting (if that's what you have) to compensate the problem you are haaving.

  3. #3
    john zigler's Avatar
    Join Date
    Aug 2006
    sounds like you have a fuel related issue.

    did you determine, and fix what caused the engine to fail the first time?

    i would rebuild the carb, ( use ONLY genuine carb manufacture kits, ie. kehin, or mikuni)

    also replace fuel lines, filter, and check the fuel select valve for restriction.

  4. #4

    Join Date
    Dec 2006
    On a stock 750 50:1 is fine. The pump won't fail on that ski but the inline filter will and will cause motor failure premix is a good idea for that ski. I had a 750 zxi years ago with a coffmans pipe, westcoast head, rejet kit with flame arrestors, TDR waterbox, impeller, plate, and it ran high 50's but was very very quick because of its weight. I ran premix because of motor failure when the motor was stock because of the filter and went back with built up motor wiseco's and stuff like that and premixed 40:1 and never failed me again and ran prob 600 plus hrs just guessing.

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