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  1. #1

    xl800 hard to start

    So if this ski sits for more than a week without being run it won't start. When I am going to run it I have to pull the carbs and pop the needles loose from the seats. They now have about a tank of gas on then and I'm back to pulling the carbs again. That pretty makes it junk. Once I reassemble it, it works perfect. I wouldn't expect a new ski to run this good. I've replaced the needles and valves the last two times. I cranked it Monday, now Saturday and I want to go ride tomorrow and it won't start. I think the spring pressure is to high, pop off is about 80 pounds and the rubber valve tips just compresses into the assembly. From what I understand it is supposed to be that high. The valves are stock 1.2's. the springs are what I got in the mikuni kit then the stock ones that were in it, then ones from my other xlt800. Is there a better combination for this ski and it still run right? Obviously I am missing something. Looking for some insight.


  2. #2
    dannyual777's Avatar
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    You have to tear the carbs back down each time just to get it to start??

    My two older, 2-stroke skis require priming if they've been sitting for a while. Usually more than about 2 weeks. I installed primers on both skis about 2 or 3 yrs ago. Prior to that, I just used a squirt bottle to squirt some gas/oil mix into the carbs and both skis would fire right up.

  3. #3
    Yes and it's annoying. I'll try the primer bulb thing and see if that will help push the needle valves free. I think I may have a crankcase leak but when it's running it's fast with no problems I can perceive. First I am going to check crankcase pressure and vacuum and make sure it's got enough pressure to operate the fuel pumps correctly. Then I am going to buy larger Yamaha needle valves. I had a boat motor that was like that. I let it be someone else's problem.

  4. #4
    dannyual777's Avatar
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    Quote Originally Posted by mpyrol View Post
    Yes and it's annoying. I'll try the primer bulb thing and see if that will help push the needle valves free. I think I may have a crankcase leak but when it's running it's fast with no problems I can perceive. First I am going to check crankcase pressure and vacuum and make sure it's got enough pressure to operate the fuel pumps correctly. Then I am going to buy larger Yamaha needle valves. I had a boat motor that was like that. I let it be someone else's problem.
    Why are you going to do this? This will change your pop off pressure and will not solve your having to tear the carburetors back down each time to start the engine.

    Your needle valves should not be sticking together just because your engine hasn't been started in a short while. If it's been many months (more than 6 maybe?) then yes, they can and will stick. It's happened to me. However, when my two 2-stroke skis sit for 2-3 months at a time with ethanol gas, my needles and seats don't stick together in that short amount of time.

  5. #5
    Myself's Avatar
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    If you have any sort of octane booster or drying product for water in the gas, the needle tip can swell and stick. Other than that, lower popoff to about 45psi.

  6. #6
    Stock pop-off was 76psi, I don't recall it being too high. I am certain
    it ran just fine for a long time on that pop-off.

    So what has changed?

    Occasionally, I have rebuilt carbs with stuck needles, but the cause was
    always obvious. Genuine Mikuni parts don't swell and get stuck closed in
    a week in California.

    Either there is something different about your needles, or it's is just acting
    like any other hard starting Yamaha, and the needle and seats are not opening.


    A common problem, people often blame on fuel pumps. Doesn't start if there
    is no gas in the float chamber.

    Quote Originally Posted by dannyual777 View Post
    I installed primers on both skis about 2 or 3 yrs ago.
    Primers make the symptom (hard starting) go away, but it doesn't fix the problem.

    Quote Originally Posted by mpyrol View Post
    I think the spring pressure is to high, pop off is about 80 pounds and the rubber valve tips just compresses into the assembly.
    From what I understand it is supposed to be that high.

    Is there a better combination for this ski and it still run right?
    Obviously I am missing something. Looking for some insight.
    Carb and intake gaskets leaking are a common problem, that isn't helped
    by Yamaha's poor machining.



    Bill M.

    When all the vacuum leaks are repaired, Yamaha's run fine with there
    stock needle and seat.

    You didn't mention your accelerator pump.

    Manufactures used accelerator pumps to lean out the pilot circuit for
    emissions testing. Lean pilot circuit's also improved gal/hr sats.

    If your accelerator pump is non - opp, you should update the jetting.
    Last edited by wmazz; 11-24-2020 at 03:17 AM.

  7. #7
    dannyual777's Avatar
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    Quote Originally Posted by wmazz View Post
    Stock pop-off was 76psi, I don't recall it being too high. I am certain
    it ran just fine for a long time on that pop-off.

    So what has changed?

    Occasionally, I have rebuilt carbs with stuck needles, but the cause was
    always obvious. Genuine Mikuni parts don't swell and get stuck closed in
    a week in California.

    Either there is something different about your needles, or it's is just acting
    like any other hard starting Yamaha, and the needle and seats are not opening.


    A common problem, people often blame on fuel pumps. Doesn't start if there
    is no gas in the float chamber.



    Primers make the symptom (hard starting) go away, but it doesn't fix the problem.



    Carb and intake gaskets leaking are a common problem, that isn't helped
    by Yamaha's poor machining.



    Bill M.

    When all the vacuum leaks are repaired, Yamaha's run fine with there
    stock needle and seat.

    You didn't mention your accelerator pump.

    Manufactures used accelerator pumps to lean out the pilot circuit for
    emissions testing. Lean pilot circuit's also improved gal/hr sats.

    If your accelerator pump is non - opp, you should update the jetting.

    I'm going to call you out on this and have you tell us what the problem is. Not trying to be mean or unfriendly and I apologize if it sounds that way over the internet. I've seen this phrase before but no one seems to actually identify the problem for those of us suffering from said problem.

    Many of us mechanically inclined people can fix a problem if we can identify it. The difficulty is always identifying the actual problem. I've read countless threads over a decade and a half and I still can't tell anyone what is actually wrong to cause an older ski to now need a prime to start when it didn't need that when it was new.

    BTW, I only use genuine Mikuni carburetor rebuild kits. My last pair of carb rebuilds were for my 1994 Raider (owned since brand new) back in the spring. I just realized that I've never tried to start it without using the primer. It's been 7-8 weeks since I last rode it. The next time I think about it, I'm going to try to start it without the primer and see what happens. One more piece of info: it's only been run with ethanol-free gas since the carburetor rebuilds.

  8. #8
    That is not a problem.

    Hard starting is the most common carburetor problem on all of the 2 stroke watercraft
    brands. My definition of hard starting is nearly the same as the OP, and I used to test
    for hard starting on every tune & service. Depending on the brand and model, if I wrote
    the R.O. (repair order). I would see how long it takes to start the engine. If it was a
    550/440, I tested the front main seals for vacuum and/or pressure leaks while the engine
    is running.

    My definition is: After sitting for a 1 week, if the engine takes longer than 1 minute to
    start, it is hard starting.

    Hard starting is normally caused by vacuum leaks on the carb base, intake manifold, reed
    gaskets, and on some engines a leaking front main seal. On the Kawasaki 440/550 this
    (front main seal) was a large problem because Kaw vented the front cover to atmosphere.

    On Kawasaki (Keihin CDK2), Yamaha, and Sea Doo a common problem was the gasket surfaces
    were poorly machined, or on Sea Doo, they relied on die casting to create a flat surface.

    A vacuum leak that causes hard starting on a diaphragm carb, would be nothing but a minor
    nuisance on any engine with a float bowl. The difference is: float bowl carburetors have fuel
    in the float bowl during starting, and the float chamber on a diaphragm carb is empty.

    So, when a diaphragm carb is hard starting, it is because the needle and seat doesn't open.
    When an engine idles and dies (common on stand-ups), it is because there is not enough
    manifold vacuum to keep the needle and seat open. So it closes, and the engine runs out of
    gas and the engine dies (because the float chamber is empty).

    When the needle and seat doesn't open, many people will see it as a fuel supply problem,
    and blame the fuel pump, gas lines, or tank. Anything but a vacuum leak.

    On most twin, triple Yamaha's, the carb base gasket, and base gasket surfaces on the carb
    and intake manifold adapter plate are a large problem because often the carbs are not removed
    intake manifold adapter plate during a carb rebuild. Of course the intake manifold adapter plate
    is also a problem.

    I worked between 79' & 2004' as a tech for performance manufactures and huge dealerships that
    sold 100 watercraft a month. During that time, I never repaired a watercraft that didn't run and
    start as expected after the vacuum leaks were repaired. That includes Yamaha with their sky high
    pop-off carburetors.

    So when I see a thread that suggests the pop-off is too high, I try to explain there is a reason
    for it, and that reason isn't what you read on watercraft repair forums.

    And most people do not know what pop-off does anyway, and are quite willing to change it
    to some arbitrary # someone read on the internet.



    Bill M.

    In general, Yamaha carbs are a special case, they were designed to run with really high pop-off.
    Even though they look like aftermarket Mikuni's, they are not the same. The 800 uses the highest
    pop-off combo available (1.2 with 115gr @76psi), while Sea Doo runs 2.0 with ~95gr @25psi. With
    most Yamaha carbs, there is a reason for why it can run the high pop-off. I doubt the Sea Doo
    carb could run the higher pop-off without significantly changing the low jet.

    That said, I don't disagree with Myself, an 80gr spring and a 1.2 has a 48psi pop-off. I have not
    tried it, but it should work, might be on the rich side. But it should run fine without the accelerator
    pump.

    Fix the problem by either flat sanding all the gasket surfaces, and replace all the gaskets. Or make
    your own thick gaskets using FelPro 1/32", or 1/16" rubberized felt from your local NAPA.
    (I can provide part #'s)

    Generally I recommend using oem carb base & intake gaskets only once. On older Kawasaki's, I
    tested reusing carb base gaskets, and they required a 1/4 turn increase on the low speed (pilot)
    screw(s) to compensate for the used gasket.
    Last edited by wmazz; 11-24-2020 at 03:06 PM.

  9. #9
    Quote Originally Posted by dannyual777 View Post
    The next time I think about it, I'm going to try to start it without the primer and see what happens.
    It may work without a change, if there is a very low idle.

    Or you could set the idle speed to '0' and leave it shut until the engine kicks, then crack the throttle.

    Quote Originally Posted by dannyual777 View Post
    One more piece of info: it's only been run with ethanol-free gas since the carburetor rebuilds.
    I don't worry about ethanol while using oem parts. We have had ethanol in California since the early 90's
    and had no significant problems with OEM parts.

    That said, I have seen Chinese main seals literally melt.


    Bill M.

  10. #10
    Thank you. There is no substitute for experience and most companies engineer their products to work at least those who stay in business. So.., I am looking for vacuum leaks. I'm going to pull the exhaust and check the crankcase for leaks first, then I am going to use my straight edge to check the machining on the throttle plate and top of the reed cage. Any further back and the leak down testing should catch it. I'll cut some aluminum for block off plates.

    I use the Felpro 3/32 gasket all the time to make gaskets. The OEM gasket are shiny with a bead of something around the holes. I'd rather cut my own instead of buying more gaskets.

    The accelerator pump appears to be fine. It could have failed since the last time it was running.

    I'm headed out to pull this down. I appreciate all your input and time. I'm in the middle of designing new decals for this ski, I should probably get it running right first.

    Brian

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