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  1. #1

    2001 gtx ltd runs on one cylinder

    Hi guys ,got handed a 2001 gtx ltd with a number of problems,the major one being it didn't run right. The ski would start and run fine on trailer and then in water but once you got over 4000rpm it would stop or start slowing with no power. Simple fix pull carbs apart and couldn't believe how it could run at all with all the rubbish in the carb filters and water seperating unit.Anyhow gave everything a massive clean up and re tested. The ski now would only run to about 3000 rpm and struggled to get on plane. Back to the workshop,cranked over engine with plugs removed and no.1 cylinder was pumping out volumes of fuel vapor and black ,very black soot was running out of exhaust.I decided to replace the gaskets in no.1 cylinder with new mikuni ones and thought i'd found a gasket in the wrong position.Thinking i'm on the right track now did another water test and still no improvement, won't go over 4600 rpm , front cylinder is cold to touch , the rear is quite warm as it should be.
    OK so surely it must be an ignition problem. Coils tested within specs with ohm meter.Changed plugs and trimmed leads.Still no change.Must be a coil problem. Changed coils over and made no difference. I'm about to admit defeat, can anybody suggest something.Much appreciated.


  2. #2
    canuck's Avatar
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    Did you check the reeds on the bad cylinder ?

  3. #3
    hi canuk, i didn't check the reeds because the compression test shows ok. 140 mag - 145 pto !

  4. #4
    canuck's Avatar
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    A broken reed will not affect compression.

    A broken reed will allow some of the fuel air mixture back through the carb instead of up the ports and into the cylinder when the piston is on the down stroke. When this happens it runs like it's on one cylinder.

    I had this happen on my old 98 GTX Limited, one of the reed petals broke and it ran like crap and would not even get on plane.

  5. #5

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    change the plugs and go through the carbs again. Pay attention to the fuel pump, check valves and diaphragm. you can check the spark on both cylinders to see if it is firing with the plugs out, but make sure you don't catch the ski on fire. If going through the carbs changed the way it ran, I'd say its a fuel problem rather than electrical.

  6. #6
    i've never had a broken reed in all the stock 951 engines i've worked on which is why i never looked, but if you've experienced this same situation i guess i've no choice but to pull the carbs, again. Thanks for the info.I'll keep you posted.

  7. #7
    hi pacer, i did change the plugs in the beginning as well as trimming about 3/4" of the leads.I also pulled the carbs apart for the second time and fitted new gaskets , diaphram, and check valves without success.It still ran on one cylinder,apart from the cold front cylinder it makes a totally different sound.I had also ran the plugs attached to the leads, plenty of spark there (and no fires). I'm stumped and time is a rare commodity.Thanks for your input though.

  8. #8

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    If it has spark, and it has compression, it can only be fuel right? I had one that wouldn't start, and had sporadic fire. It turned out being a ground wire that had pulled loose from one of the MPEM plugs. It was acting like a sheered flywheel key. I've never sheered a 951 flywheel key, and the only time I've had a mag go out was when it got full of salt water. But It doesn't sound like spark is your problem. I would spray some carb cleaner in that cylinder and see if it would pop on only that one (probably not a recommended method).

  9. #9
    PACER It's got spark, it's got compression,it's had the carbs cleaned and refitted twice, it's got me totally bamboozeled. i guess the only thing to do is take it all down again, replace the ancient fuel lines which if there not part of the problem they soon will be and maybe like canuk suggested, try the reeds. But none of it makes any sense when it was going fine one season then a piece of cr-p the next, but hey that's marine engines for you. Thanks guys.

  10. #10
    Myself's Avatar
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    Measure your battery voltage while cranking. What is it? Now measure while it's running and rev it to around 4000 rpm. What does the voltage read?

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