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  1. #1

    Accelerator pump woes

    Hi I have a guys 1200r Australian here, I did a rebuild on it (crank, pistons and carbs) and in a short 15 minute ride I squeeked the 1 and 3 pistons lightly, or well just enough to damage the plating on the cylinders,
    Would a split in the line from the carb to the acc pump be enough to seize at revs below 4000, but the pump is working fine with no blockages.

    now I've also heard that if you fit steel sleeves into the cylinders that you have to richen it up slightly
    01 gpr 1200 Aust
    l/s 92.5
    h/s 135
    gold spring
    n/s stock
    it has d plate stock

    another question is, if I fit the steel sleeves which is getting done now and remove the acc pump, what jetting would be a good starting point


  2. #2
    Moderator OsideBill's Avatar
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    The jetting is way off base you had a midrange lean seizure. I have my 1200R set-up like this. Remove or disable accelerator pump, 110 lows, 125 highs, 1.5 N&S, 95 gram dull silver spring. This was proven by many people to eliminate the midrange seize issue, and give crisp throttle response throughout the range.

  3. #3

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    The accellerator pump is there to help you get past a mid range lean spot. If you remove it, you are subject to a lean seizure.

    To deal with this problem, you need more fuel on the bottom end (larger pilot jets) and for extra fuel to be delivered earlier (lower pop off).

    Lots of riders have gone to this set up:

    110 pilots
    120 or 125 mains
    95 gram spring
    1.5 Needle and seat (Pop off at 40-43 psig)

    This is all assumeing that you will be using aftermarket flame arrestors which are for the most part free flow. The stocker flame arrestor create a different signal (vacume) then aftermarket. I do not think this set up will work for you if you choose to keep the stocker on your boat.

    Also, if you remove your accellerator pump, you loose your primeing mechanism. You would have to add an aftermarket primer. You can "disable" your accellerator pump so that you can manually reach under your pipe and prime by pressing the button yourself. It is a hassle, but it works.

    Be sure to plug the nipples you would expose on the carbs if you pull the pump.

    I do not mean to confuse you, I just want you to know what you are getting into if you remove the accellerator pump. The 1200 is known for haveing a lean condition.... you can do a search to find how many people have lost cylinders and pistons because of this issue.

    It's one of those "in for a penny, in for a pound" kind of things. If you are going to make a change like removeing the accellerator pump, make sure that is done completely and right.

    IMHO, going to steel sleeves is not the way to go. The nicksil cylinders are more tolerant of mild lean siezures and handle a bit more abuse then steel given the same conditions.

    Hope this helps.

  4. #4
    Moderator OsideBill's Avatar
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    Here is a link to Island racing scroll down the page to find the yamaha 1200R carb rejetting kits. Note that they include the accelerator block off kits
    http://www.islandracing.net/watercraft.html

  5. #5
    Moderator beerdart's Avatar
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    Quote Originally Posted by salty View Post
    The accellerator pump is there to help you get past a mid range lean spot. If you remove it, you are subject to a lean seizure.
    The accelerator pump is a one time deal it only squirts once as the throttle is advanced. Prolonged 1/2-3/4 throttle is where the lean mid is and the accelerator pump has nothing to do with cruising at 1/2-3/4 throttle. Take the thing off re-jet and be done with it. Just a couple of pennies from me.

  6. #6

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    I agree with you beerdart. If you are just cruising in mid range on a stocker boat, there should be no problem, especially with the stocker flame arrestor. It is when you accellerate in the mid range, that is, when you need extra fuel to be delivered right now...... that is when I think that he would have a lean problem. That is why I believe the pump was put there.

    I have since gone with virtually the same jetting that most members with 1200's seem to have gone with, and it works extreemly well. I just want winterstick to understand is that there is more to this than just jetting and that it should not be taken lightly. He needs to consider flame arrestors and a primer kit. If he does it the way many of us have, he should not have any problems.

    My apologies if I am misunderstood.

  7. #7
    Quote Originally Posted by osidebill View Post
    The jetting is way off base you had a midrange lean seizure. I have my 1200R set-up like this. Remove or disable accelerator pump, 110 lows, 125 highs, 1.5 N&S, 95 gram dull silver spring. This was proven by many people to eliminate the midrange seize issue, and give crisp throttle response throughout the range.
    The only thing ive done to the carbs is put a rebuild kit throught it, it's the original jetting and other specs is for the Aussie gpr the only thing wrong was the split in the fuel line to the acc pump, which is what I was wondering if it would cause the seize, its still in operation but not sure if its getting the fuel required, I eventually want to remove the acc pump, keep the stock f/a box and it will have the steel sleeves as replating here will cost $1200 +
    its not mine and i don't want it back again

  8. #8
    Moderator OsideBill's Avatar
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    If you seized the cylinders it was either a lean condition or they did not get oil. The accelerator only gives a squirt when you pull the throttle off idle. you can verify this on the little cam on carb #3. I do not think the split hose would cause a lean but it may have. possible that it caused the other carbs to be starved for fuel at top end. I still feel the jetting is on the low side. hope this helps

  9. #9
    All hail the Chief! fullboogie's Avatar
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    Salty's explanation is spot on - that's all the info you need.

  10. #10
    Mongoose's Avatar
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    The jetting specs are oem export specs with a factory d plate.
    I really don't think that's your problem. If you have not touched the stock airbox, then they should be fine.
    You either seized because of lack of fuel, or lack of oil.
    Were you running low on fuel when this happened?
    Are all your oil lines all ok?
    How many hours on the carbs?
    i would verify that the carbs are getting fuel and oil. The small internal carb filters could be blocked-

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