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  1. #1

    Still new here - Carb adjustments, rebuild, or jets?

    Hey guys, Still kinda new here, but believe me I'm already pretty deep "into this stuff".

    I've given my 2001GPR about 3 hours worth of time so now the clock reads 58 hours, and noticed something I didnt like to hear on the water. Slowely increasing the throttle beyond about 1/4~1/3 and before the powervalve 'vtec' hits creates a little after-burn affect, which by my experience is a lean condition. Basically, the engine hesitates very very slightly (Practically un-noticable), followed by a small but audible 'pop' downstream in tail of the exhaust. This would represents a misfire (lean) and then unburn fuel exploding in the exhaust downstream. A second but slighter symptom I have is 3/4 to WOT, where there really isnt much difference at all going further than about 3/4 throttle. The ski ran 62mph yesterday. 3rd, after engine warms up the idle is a little out-winded with hot-restarts without a slight throttle blip. Once going it runs just fine.

    Back at home, examined the new sparkplugs and found 1&2 might be going lean, but I'm taking the visual kinda loosely as plug reads arent good after idling through no-wake zones - still a concern though.

    I'm thinking this boys; is a lean condition all around. In doing some reading up on pop-up, jet sizes, and the like I decided to start getting my hands a little dirty. The former owner installed a D-Plate, and 'said' they adjusted the carbs - but the tamper plates are still on the carbs. I'm concerned that the D-Plate is being met with stock fueling which is probably alreadylean from the factory.

    I've already removed the stinger and have access to 'see' the tops of the carbs and the high adjustment which is still capped. Are the low adjusters under the carbs?

    1. My first thought is to just open the low and high adjustments about 1/4~1/2 turn c'clockwise as this is probably the quickest thing to try, and the least costly atm under the current state of things. This would mean taking carbs-off, pull tamper, twist the screws with a screw driver, and re-install, test and repeat if necessary.

    2. I was thinking if #1 didnt help, then go straight to getting the carbs re-build with a proper jet-kit, pop-up, and T-Handles, to the tune of $300+. I dont honestly have budget for something like this. If #1 gets me through the summer than I can definately do #2 later on.


  2. #2
    Popped off all the tamper caps. I found a mix of factory settings for which I cannt be certain that my careful drilling didnt poke through, grab the screw, and change on me. Cyl1 had both adjustment fully closed, and others had on average about 1.25 turns. I went ahead and set up a baseline of 2 turns out on all low and high screws, and tonight should be able to give it a go and let this thread know how it worked out.

    One other thing I found was that some of the head bolts were actually not torqued down to spec, and a few needed ~1/2 turn to get there. Apaprently the head has been off previouslly but I'm unable to tell if the motor was actually pulled from the hull. Hopefully not.

    Im very surprised at how easy it actually is to work on this engine and I'm starting to put my worries behind.

  3. #3

    Join Date
    Aug 2006
    In the FAQ read the ones about Carburator Drilled Returns, and GPR/XLT Carb upgrades.
    If you buy flame arresters and do these 2 mods, you have a greatly better running boat, and a safer, more reliable setup.
    No questions asked, just do it. Everybody who has never looked back.
    Installing a D plate does not effect jetting needs at all.
    2 turns out on the lows will not be a satisfactory idle and low end for sure.
    The high speed screws only help at the top, 7/8 to full throttle up.

  4. #4
    Ill start to read those over as i didnt before; thank you

    I wouldnt want a funky idle so i tested the settings oit tonight in the driveway. Seems idle is just about the same as before from what i can tell. My guess is in the water it will be a bit different.

    I ordered some t handles for the next time carbs need to be removed. Also ordered riva intake andpump seal. Looks like staying stock has gone out the window.
    Thank you

  5. #5
    SMLaker's Avatar
    Join Date
    Sep 2008
    Get the bug eh? 1-turn out on the lows should be fine. 2-turns is too much. .75 to 1.0 on the lows, 1.5 on the highs. Rear cylinder high 1.75 turns. It runs leaner than the other two.

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