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  1. #1

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    pressure test with carbs on ?

    Can I do a pressure test with the carbs on ? Iam rebuilding the carbs and am trying to find out why I have blown cylinder 1 twice .


  2. #2
    Moderator OsideBill's Avatar
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    No you have to have the carbs off to pressure test. Here is a motor I did while in the ski without removing the U-pipe. Generaly with the test kit I have you need to pull the pipe, I have the gauge/fill attached to the hose coming out of the #3 pulse line.
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  3. #3

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    Quote Originally Posted by OsideBill View Post
    No you have to have the carbs off to pressure test. Here is a motor I did while in the ski without removing the U-pipe. Generaly with the test kit I have you need to pull the pipe, I have the gauge/fill attached to the hose coming out of the #3 pulse line.


    I was thinking of using rubbr expansion plugs in the mouth of the carbs . I think it was fernandos thread on pressure testing with tripples looks like he did it with the carbs on .If I do it with the carbs off can I just take some gasket paper and use the stock manifold then rubber plug the exhaust . I dont really want to buy the kit from lowell because I may end up getting an sho .

  4. #4
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    I'd pull the carbs

    simply put, too many places for a leak to pop up..and then you'll really start chasing your tail. Do it once, do it ruight and if you lose another engine, you'll be pretty sure it's not a case leak.

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    Moderator OsideBill's Avatar
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    Quote Originally Posted by harleyboy61 View Post
    I was thinking of using rubbr expansion plugs in the mouth of the carbs . I think it was fernandos thread on pressure testing with tripples looks like he did it with the carbs on .If I do it with the carbs off can I just take some gasket paper and use the stock manifold then rubber plug the exhaust . I dont really want to buy the kit from lowell because I may end up getting an sho .
    I loan my Lowell test kit out with a $100 deposit, I return the deposit less my shipping fee, once it is returned. The shipping fee runs $10 for a flat rate priority box. So if you would like to use it pm me your address and we can work out the details. I used to loan it out freely, but got burned a couple times so I have to do it this way now.

  6. #6
    All hail the Chief! fullboogie's Avatar
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    Your #1 carb is last in line to get fuel, so look for pressure/flow problems. Good time to put a fuel pressure gauge in the old fuel selector location on the cowl and run dual pickup/feed lines.

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    Quote Originally Posted by fullboogie View Post
    Your #1 carb is last in line to get fuel, so look for pressure/flow problems. Good time to put a fuel pressure gauge in the old fuel selector location on the cowl and run dual pickup/feed lines.

    Well right now iam running the feed off of the reserve and the primer off of the old main line . I think it is a fuel issue but not sure the first time it blew I found a real small hole in the pulse thought I had my problem fixed . I rode for .5 tank gas on and off the throttle to break in the rings next time out i rode 30 mins then held it wide open then it blew again the same way . So here iam again . This time I rebuilt all the carbs went up on the mains and piolts checked pop off and now am going to pressure test the motor . Put a fuel pressure guage on and retune again .

  8. #8
    All hail the Chief! fullboogie's Avatar
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    Unless I am reading your post incorrectly, you do not have a dual feed setup. Some swear by it, some don't. But while you're in there, you may want to think about it.

    With respect to the pulse lines, change them all to new ones regardless of what condition you think they're in. Bottom line is that you've killed #1 twice and still don't know why. Find the problem or you're looking at the third time.

  9. #9

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    Thanks to OsideBill I was able to do the pressure test on my motor the right way . I have a 1 psi loss in 6 mins . Which from what I have read is within range . So it seems like I have a fuel issue . My plan is to rebuild the carbs, bigger jets, drill the returns to 1/8 , put a fuel pressure guage in , dual feed and possibly get rid of my primer and use the old accelrator pump as a primer instead . Does any one else have suggestions I still have not found reason it blew up or than possible weak fuel pump in #1 carb

  10. #10
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Do not pass go just yet....

    While fuel seems like an obvious reason to run lean, there are other things to consider..ignition timing for one, crank index for two.

    Putting more fuel in there may not stop this if the issue is detonation..got pics of the burned piston so we can have a look?

    and pulse lines should without a doubt be changed, even a small air lean there can make for a lean run at both ends.

    Couple of not so wide open runs and a plug check might be in order too.
    I'm assuming you are running injection, make sure the pump is adjusted correctly..too much oil wide open can mean not enough fuel.

    What's your plan if putting more fuel in there via bigger jets doesn't do it for you?

    At the least make sure tdc on the pistons is actually tdc according to the ignition system. A twisted crank could advance the timing just enough to melt it. While this was more common on polaris from what I've seen, anything is possible, especially if the engine ever had a water ingestion problem.

    just some more stuff to think about before opening hte money pit one more time.

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