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  1. #11
    i have tried to run it on a gas can with a short hose right to the pump..no different.. how do you pressure test eng?

  2. #12

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    Pete or another expert can chime in but basically a pressure test is conducted on the entire engine assy. to check the integrity of the seals that block air and water leaks. This includes crank seals, cylinder base gaskets, rotary valve cover seals, etc. If there are air leaks they will lean the air fuel mix, causing burn downs, hard starts, etc. I believe there is a kit to seal the exhaust ports, intake ports, etc. and it is a big PITA to do properly.

  3. #13
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    before going to crankcase pressure tests, I'd confirm that the carb jets are in the proper place ( reread my previous message) and then check the pop-off pressure on the carbs while you have them off (by the way you need a calibrated air pump gizmo for that , $50 at amazon ) you also need to check the carbs internal fuel filters. I've dealt with "experts" rebuilding carbs and overlooking them because they simply don't know any better. A good way to check your fuel flow is to disconnect the return line place it in a container, start the engine and let it idle, there should be a good amount of fuel flowing into this container because at idle speeds fuel demand is quite low. Having a test tank made all the difference for me diagnosing repairing and testing carb issues. Not fun doing that while standing in water at a ramp getting stink eye from everybody around. Do be careful having a fuel line off, ,the y fitting may be brittle and break if you rough handle it, not to mention the fire potential. Far safer to cut the line far from the carbs and simply put a 1/4 brass line splicer in there to connect it after the test

    pop off pressure too high does not allow fuel flow from the fuel chamber at low rpm ( low vacuum) into the engine.

    you really need to pay attention to all members suggestions. we have a really large base knowledge of two stroke engine operation here

    pulling the choke ( as suggested) can also increase the vacuum and is a good way to quick check to see if fuel starvation is really an issue.

    pressure testing an engine is kinda of a pain on a 747 and requires an air compressor and a bunch of other bits

    we know you replaced the RV cover, but how was the condition of the rv surface on the block?, leaks from a port to port gouge can totally screw the low speed to mid range transition which is where you're having your bogging.

    you also had mentioned the carb adjustments "don't work", that's a concern which is pointing to a crankcase air leak ( hence the pressure testing suggestion). "sometimes" less experienced techs damage the low and high speed needles by tightening them down too much, or in some cases leaving the o-rings off when they put them back together. pull the needles and inspect the tips with a magnifying glass. should be cone shaped with a pointy tip and no ridges you can catch a fingernail on

    so you have quite a bit of homework here. see you in a couple of days

    to review:

    1-pull choke
    2-check fuel flow from return line
    3-pull carbs, check jets and little filter, then adjust pop off pressure, check low/high speed needles
    4-pressure test if still bogging

    I'd suggest picking up the mikuni carb manual, you can sniff one out on the web, or find some good how to's somepalce to assist.

    hint: only take one carb at a time apart so you don't mix stuff up

  4. #14

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    Did you ever get this sorted out??


  5. #15
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by etemplet View Post
    Did you ever get this sorted out??

    give him a few more days, the OP got alot of stuff to do, and its not easy to muster up to go at it again when success is seeming elusive.

  6. #16

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    Quote Originally Posted by nmpeter View Post
    give him a few more days, the OP got alot of stuff to do, and its not easy to muster up to go at it again when success is seeming elusive.
    LOL I thought his last post was in August. 8 or 9 too close to call. Ha ha

    I'd go for a big fuel issue first. Pressure test the fuel line by blocking off the lines just before the Baffle. Could be the water separator. Could be the fuel valve. I've installed new ones that leak. Now I test them before I install them.

    Seadooforum.com has a great carb rebuild thread. Those things will get ya for sure. Good Pop-off for my GTXs in my area is 37psi. My wife's 97 would bog and bog at lower settings (under 30psi) It would just sit at 37mph. I lowered the pop-off and it went 27mph. I replaced the needle seat and spring with genuine mikuni parts and a friend posted a technical service bulliten that said to upgrade the RV housing and rave valve so I did. Her ski really launches now. Good Luck man !!
    Last edited by etemplet; 09-20-2020 at 01:28 AM. Reason: added information

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  8. #17
    since my last post i have made block off plates and vacuum tested the block i can pull it down to 10 and it takes a good minute to bleed off...i also ran it with an electric fuel pump with no difference.. i can cup my hand over one of the carbs and the bog goes away. This is why i have changed carbs thinking after all the cleaning and rejetting with no improvement i thought i might have a bad carb...

  9. #18

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    Quote Originally Posted by davegtx21 View Post
    since my last post i have made block off plates and vacuum tested the block i can pull it down to 10 and it takes a good minute to bleed off...i also ran it with an electric fuel pump with no difference.. i can cup my hand over one of the carbs and the bog goes away. This is why i have changed carbs thinking after all the cleaning and rejetting with no improvement i thought i might have a bad carb...
    So you are lean. Is it only one specific carb?? I'd check the ports inside the carb barrel.

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