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  1. #1

    1988 JS 440 Problems, Help needed!

    Hey there guys new user here! First post.

    I recently purchased an 1988 JS 440 with a bunch of aftermarket parts (pipe,intake,prop,ride plate etc). When i bought it i knew that the diaphragm would need rebuilding because it would not start unless it was fuel down the carb. So i rebuilt the diaphragm everything seemed to go good in terms of fuel getting to carb. Also changed fuel lines.

    So i took it out, started, hard to start off felt like running out of fuel, got up and rode around. Had hesitation when i would come out of full throttle and let it idle almost like it was running out of fuel. Eventually after 25 min of riding it died out, wouldn't start for the life of it. I let it sit for 6 hours and it worked again but same hesitation and starting problems, after it died would not start again.

    Tried a carb off a js 550 and it didn't have these problems but ran really rich but went around no problem and started fine.( carb also had a primer kit if that matters )

    So just wondering what i have to do, i really enjoy the jetski and hope i can get this guy going !

    I apologize in advance for the long story.

    Please and thank you for all input !


  2. #2
    Did you take apart the fuel pump when you inspected the carb? I had a check valve that was not closed all the way and gave me similar starting problems. I just flexed the metal valve a little to put tension back on the hole and it sucked fuel like there was no tomorrow. If you have a manual, it will likely tell you not to take it apart. There is nothing more than a diaphram, oring, and gasket in there though. It wont hurt it. If anything you may help it.

    that's my 2 cents.

  3. #3
    Thanks for response, where exactly is this piece your talking about? Is it in the diaphragm ? Sorry I just need a little more guidance then I should be good.

    Thank you in advance!

  4. #4
    Sorry, I was mistaken on the model jet ski you have. It does not have a fuel pump like the one I was referring to.

    The only check valve you have on yours is #37 in this diagram:

    If it ran with another carb, it is probably still a carb problem and not a fuel line, filter, spark, or compression problem, but have you definitely ruled these things out? They are simple to check and the first thing I would delve into before ripping apart the carb again.

    You can check to see if it has compression by puting your finger over the spark plug hole and turning it over. It should pop your finger off the hole when it turns over. Be sure to disconnect all the plugs so you don't get whacked when doing this!

    Check spark by laying the electrode end of the plug against the metal of the hole. Turn over the engine and see if it sparks. Again make sure the other plugs are disconnected to avoid starting it with a plug out and knocking yourself.

    Check to see that fuel is not being restricted from flowing through the fuel filter and fuel lines. You can do this by siphoning the fuel through the line and seeing if it runs out steady into a can. If you use your mouth, I would recommend attaching a clear hose over the line so you know when it is coming. I know you said you replaced the lines, but just make sure you check if you haven't. No fun tearing into things too far and realizing it was something simple that should have taken 5 minutes.

    If all that is in order move onto the carb. Did you rebuild everything in the carb, replace a few things, or just inspect things? Did you clean out any and all varnish, debris, and gunk that may have been in there? Just one piece of sand or debris lodged the wrong way can screw everything up. Did you spray everything including all little openings where debris could get caught with carb cleaner. Did you check the diaphrams to see if there were holes or tears in them?

    This is where I would begin. Let me know what you have done or maybe in just a little more detail and I will see if I have any other suggestions.


  5. #5
    Thank you for the help, Trying everything you said.

    Do you think switching to primer instead of choke would be smart?

    Appreciate all the advice

  6. #6
    I do not personally have a primer system in my ski, but I have considered adding one. From those who have them, they say that it resolves the hard starting problem. I think it is more that it saves you the headache of waiting as long for it to start up. In my opinion, if the carb doesn't suck fuel enough to start on its own, something is wrong, and even with priming, it is probably just a matter of time before it dies on you.

    If you want to switch to primers though, i have never heard complaints about them. Everyone who has them raves about how great they are. Just make sure you still solve the root of the problem.

    Let me know what you find.

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