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  1. #1

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    951 Carb Tuning Questions

    Just tuning my 99 xpl.

    It has pro k 's and 85 lows, 2.3 seats and 165 highs.

    I've read the carb tuning threads and initially I've just been adjusting the low speed screw. I've adjusted it between the extremes of motor stopping to too much gas so it splutters before clearing excess fuel. The best adjustment seems to make it hard to start but not certain about that yet.

    Questions are - how many turns out does the low speed screw have no effect ? and I've still got the accelerator fuel injector pump hooked up. Should i keep this or deactivate it ?

    Also how the hell do you adjust the high speed adjuster without eyes on the end of your rubber arm ?

    Thanks,

    Phil


  2. #2
    Do you have a running problem??

  3. #3

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    3 turns out max

  4. #4
    SURFnTURF's Avatar
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    Lows 85 usually work best at 1.5 turns open and the highs should be closed or just open at 1/8-1/4 turn .
    After any adjustment you need to let it run through the rev range to set the carbs properly.
    85 is a touch lean I like 87.5 with pumps or 95 with no pumps.165 is good for the highs

  5. #5

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    ok thanks for that - yeah high jet is about 1/4 out and 1 1/2 on the low adjuster was were i got to.

    Ski is running ok but I'm chasing some lost performance - i rejetted it and put on the pro k's and it went like a cut cat from standstill. From stationary, give it full throttle and it would pause for say half second and then practically leave the water. Never got round to tuning carbs as it developed issues.

    lost some power - diagnosed as a cracked tuned pipe letting water in - sorted that and it went back to pause then cut cat.

    then just going along doing nothing in particular and there was a "blip" - (like a stick going through the jet unit or something) and it just lost some power. Still went ok but not great. Peak revs fine just acceleration is down

    Stripped the top end looking for the broken reed or failed gasket or whatever. Nothing wrong - changed all the gaskets - re kitted the carbs, checked the magneto, checked the jet unit. no problem founds. Still see the honing marks on the cylinder walls. checked the tps, rave valves, water regulator

    So now it's back together it's still not got the same get up and go so i'm adjusting the carbs - so far adjusting the low speed has made an improvement.

    Only things that worries me is that when it was stripped the cylinder domes and head were spotless - like almost brand new still shiny. I thought this was diagnosing a water leak but nothing - even pressure tested the cooling system after it was re built and all good.

    Two tanks after the rebuild looking down the plug hole with the raves out they are still spotless - i'm using castrol tts - fully synthetic oil which at the price should be good but never had a 2 stroke burning so clean.

    I plan to go through all the electrics next but not hopefull i'll find anything. Apologies for long mail but it's getting bloody frustrating

  6. #6
    SURFnTURF's Avatar
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    If its dying just after idle usually its the accelerator pumps not squirting fuel.They gum up with crud at the orifice in the carb. Pull them out(pliers twist and pull) and soak them in carb cleaner or fuel and poke a small piece of wire to get the crud out.

  7. #7

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    I have the same 85/165/2.3 jetting in both my 99 XPL's and RX's. Lows are open 1 1/4 and highs shut. Heads are all cut down to 42.3cc installed, with no more than 0.070" squish. The skis will stand straight up and nearly rip your arms off when accelerating. No lag or hesitation. Sometimes a very slight studder after long idle periods. If you dont have any other fuel delivery issues, jetting is good assuming the gas available is decent. Everything I installed 167.5 highs lost rpm. If you do end up with the larger highs, make sure they are shut completely. Things I would look for closely to help eliminate the carbs as potential problems.

    Clear round disks for fuel pump-make sure they are not kinked or cracked around outer diameter.
    Large black metering diaphragm-it needs to be babys butt soft and supple feeling, should not crackle when flexing.
    Black pumping diaphragm goes against the stack with matching clear mylar next.
    Recharge jet in the rubber feed line from carb body to accelerator pump needs to be in place and not restricted. 0.032-0.035".
    Check valve in accelerator pump confirmed clean and functioning.
    Accelerator pump arm properly adjusted with correct clearance set before throttle is applied.
    Fuel selector valve conformed not leaking between ON and RES.
    Fuel selector valve not restricted.
    Fuel return orifice in carb body not restricted.
    Carbs properly synchronized.
    Fulcrum arms both set the same and flush with metering block.

  8. #8

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    Carbs just been re kitted and carb cleaner squirted everywhere so i thought carbs were good.

    Bang on surf n turf - Just taken flame arrestors off and looked down the the carby throats and can't see any fuel squirting from the accelerator pump into the carbs. so that's first thing to get working. Must have missed a check valve

    Timebomb - What's proper clearance of accelerator pump ? and what does "Fulcrum arms both set the same and flush with metering block" mean ?

  9. #9
    SURFnTURF's Avatar
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    Yes usually if one blocks up both soon thereafter.

    The clearance for the accelerator pump is when the engine idle is set to 1500rpm out of the water.
    Engine off you set the clearance between the accelerator pump plunger and the lever tab with a feeler gauge, it should be between 0.05-0.15mm or .002-.005in.

    The fulcrum arms are the pivoting arms between the black diaphragm and the needle and seat.
    With the springs fitted they should sit flush with the flat section of the carb body (metering block)

    Fix your check valves in the injectors and this will fix your hesitation just off idle.

  10. #10

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    So with the carbs out I'm thinking about replacing the accelerator pump with larger low jets as surfnturf mentioned as an option.

    Anyone know what the pros and cons are ?

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