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  1. #11
    Moderator OsideBill's Avatar
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    The drilled return mod allows all the fuel pumps to work together, it also balances the pressure. This is how I run all mine. I have one going on three years now without an issue, and it sees the hardest use. I am not sure what an anti siphon valve is? double up on the check valve under the valve body assembly. The part number is BN34/107, check valve (clear) I use a new one from the kits when I rebuild and put the used one on top of it.


  2. #12
    Bill
    Is there a post anywhere on here that describes exactly what you do to equalise the pump pressure etc as described above

  3. #13
    Moderator OsideBill's Avatar
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    It is quite simple really, when you have the carbs apart you drill an 1/8" hole in the carb body where the built in restrictor is. This is on the fuel pump side, the small hole that goes out to the fuel fitting. Do this on all three then you install a jet in the return to tank line, there are several ways to do the jet. On the older 1200's I tap a 4mm thread into the last tee where the line return's to tank and install a 95 pilot jet, on the gpr's I do the same except with a 5mm tap and a main jet. You can also tap a fitting or buy them from Riva ready to go. Pics attached
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  4. #14
    here are some updates followed by thoughts.

    repaired the pumps with new valves, confirmed the pop-off 10 times at 76psi with the 1.2 seat and silver spring.

    the pto carb is "ok" however the mag carb and center carb still dribble/piss from the venturi.

    decided to check everything else, the reeds are in very good shape, the timing sensors on the mag and everything are good, i replaced the ignition cables and ends with new hardware and checked it over. yes i did not just cut the ignition cables on the coils, but i completely removed them and installed new ngk wire.

    the engine still has issues with the dribbling.

    so i then removed the inlet checkvalves completely, installed a 6psi electric pump and checked the pop off again, installing the gold spring. the pop off is super high now, and i "reamed" the return line restrictors with a 20 thou drillbit to ensure they are clean and not plugged.

    running with the electric pump is a rock solid 5.5 psi, with the engine off all the carbs are ok and not dribbling or leaking through either the idle port or the venturi port. starting the engine the carbs are ok until about 30sec after starting, where the center carb begins to dribble, then followed by the mag carb.

    dispite everything i do, it is ALWAYS the mag and center carbs that dribble. raising the pop off has no effect, nor does switching the needles to other needles i have lying around. the engine is in perfect working order as are the electrics.

    i have checked all the fuel lines and all are ok there are no restrictions to the tank... i have yet to check the tank vent valve for proper functioning.

    i want to verify the ignition timing but i need to degree my coupler so i can utilize that as a reference with the engine working.

    this is becoming very frustrating.

    lastly.... equalizing the pressure of the pumps with drilling out the restrictors and installing a return line restrictor.

    would it not be easier/better/cheaper to install a needle valve (flow control valve) instead of a mikuni jet in a line splice as the pump restrictor? it would make the pressure tuneable, and thereby give you the ability to adjust it to suit your needs. it would be quickly tunable for those who do not have a plethora of mikuni jets lying around. And these valves can be picked up at a hydraulics supply store. Many having lockable settings and good o-ring seals to thousands of psi, that are compatable with gas (buna-n or viton).
    id like to think it would make the air fuel ratio at higher loads adjustable on the fly from the dash instead of monkeying around under the seat several times. (aslong as the carbs are synchronized.)

  5. #15
    Moderator OsideBill's Avatar
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    I put a tee in screw the mikuni jet into the outlet side of the tee the inlet side comes from the carbs and the branch of the tee goes to my fuel pressure gauge if I want to TUNE it I simply change the size of my jet and monitor the pressure on my gauge. How simple do you want it?

  6. #16
    Quote Originally Posted by OsideBill View Post
    I put a tee in screw the mikuni jet into the outlet side of the tee the inlet side comes from the carbs and the branch of the tee goes to my fuel pressure gauge if I want to TUNE it I simply change the size of my jet and monitor the pressure on my gauge. How simple do you want it?
    sorry, lol. i come from the land of cockpit tuneable engine management, so kind of expect a bit more ease when it comes to making adjustments.

  7. #17
    Moderator OsideBill's Avatar
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    Quote Originally Posted by the_natrix View Post
    i replaced the ignition cables and ends with new hardware and checked it over. yes i did not just cut the ignition cables on the coils, but i completely removed them and installed new ngk wire.
    Can you please explain in detail how you performed this mod? material, tools used and method, I have a need to do this and have not attempted this before. Thanks in advance Bill

  8. #18
    not a problem, i've done this on all my jetski's and a friends.

    you need to first get either 7mm or 8mm copper core ignition wire. You must use copper core style, not the american auto graphite core.
    spiral wound wire would work too, but its resistance is a bit high.

    you can get pre made wires from ngk that have a boot bonded to the wire with the correct terminal end (sae sparkplug clip) or you can get the wire and the sparkplug caps separate. This is what i did for my gp1200.

    once you have everything, you need to remove the ignition coils from the electrical box. disconnect them inside and then unbolt the clamp that mounts them onto the ignition box.

    now simply cut the zip ties on the coils boot, and the sparkplug boot, and unscrew the old sparkplug boots. also remove the extra peice of insulation hose. before we go any further we need to slide the ignition coil itself out of its protective boot, and you can use the ignition wire to help force it out.

    with the coils off and out of their boots this is the delicate part. you need to first, cut the wire off flush at the coil end. this will leave some of the ignition wire inside the coil's port and it is glued in there. do not freak out. to remove it you need to make a tool to "drill" out the old rubber from the wire.

    to make the tool i used a peice of 3/16 metal brake line, however a 1/4 inch peice would work better. cut the peice so it is about 5 inches long.
    with the peice now mounted in a vice, use a hacksaw or a dremel disk grinder tool to slot one tip of the pipe so it is forked about 1/4 inch deep. do this again 90 degrees so there are 2 cuts producing 4 slots.
    those slots will dig and clear out the old rubber from the ignition cable.
    the fact that the tool is hollow will allow us to drill out the left over ignition wire insulation, without damaging the contact pin inside the coil.

    with the tool now securely mounted in a hand drill using the lowest speed slowly drive the tool into the remaining ignition cable in the coil. do not try to remove all the material in one shot. go little by little 1/8 of an inch at a time, sooner or later you will feel the tool bottoming out on the coil's plastic and you know to stop.
    while you are going you can also stop from time to time to clear out the tool and use a pick or small screwdriver to dig out some of the ignition cable insulation.

    as you remove the insulation some of the ignition cables conductor will become more exposed and you can pull it out with a pair of needle nose screwedrivers. you may find some old glue still stuck to the coils port walls, so try to dig that off too if you can. becareful not to bend or damage the contact pin inside, it will be fairly obvious what is the contact pin and what is the old wire... but to be sure the contact pin is brass and about 1/16th of an inch in dia, cleanly machined, no screw threads. the wire will be gnarly multistranded copper that is easily pulled out.

    once its all gone, the hard part is over.... now you simply need to cut the new ignition cable 2-4 inches longer then the old cables were, and then shove them onto the contact pin inside the coil's now clean port. once you have test fitted them in the coil, and satisified with the connection, you need to remove the wire, sand the wire the same length as the depth it fit in the coil to rough up the surface and coat the outer perimiter in epoxy glue. re install the wire into the coil and mount it in such a way that it can cure with the coil wire pointing up.

    once its all done its simply the reverse of the disassembly. once the coils are back on the electrical box you will have the bare ends of the wires sticking out over the motor, and then you can route and trim them so they best suit your style and needs. then simply screw on the new terminals if you bought separate terminals.

    http://cgi.ebay.com/ebaymotors/NGK-spark-plug-resistor-cover-PLUG-CAP-WATER-PROOF_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el111 6QQhashZitem3eef1fb82cQQitemZ270299805740QQptZMoto rcyclesQ5fPartsQ5fAccessories

    thats the cap i used, however i purchased mine locally. you should beable to find them in a power sports store or auto parts store. the gp1200 requires a 5k ohm resistor in the cap, and those provide it.

    http://cgi.ebay.com/ebaymotors/Buggie-Atv-Quad-Go-Kart-Parts-Ngk-Ignition-Coil-Wire_W0QQcmdZViewItemQQ_trksidZp3286Q2em20Q2el1116 QQhashZitem27a564fb67QQitemZ170278583143QQptZOther Q5fVehicleQ5fParts

    thats what i used on my blaster, but the splicer went into the trashcan...

    i'll post pictures when i get back in town.

  9. #19
    ok here is a quick update and a few photos of the wires+coils.

    if you need i can take the coils out of their boots so you can see the bonded connection of the cable to the coil.

    anywho... the fuel dribbling even occurs under situations of ZERO fuel pressure. so its almost as if the high speed checkvalve "anti-siphon valve" is leaking too easily for somereason.

    i dunno, im gonna try and double them up and see where it goes.
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  10. #20
    Moderator OsideBill's Avatar
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    Nice write up, I am going to give this a try.

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