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96 SPX After Carb Rebuild

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  • 96 SPX After Carb Rebuild

    The rebuild of the carbs was pretty straight forward, thanks to your help, carb rebuild guidelines and all the related postings! The ski had a new engine installed less than two years ago and the owner before me had the stock airbox replaced with K&N flame arrestors. The needle valves were at 44 PSI before my rebuild, now they're at 31-32 PSI as Bill O' suggested. I replaced both needle valves during this rebuild. Also, just as he said, backing the high speed screws out a little cleared up the acceleration bog instantly. The problem now is that it has developed a hard and hot starting condition. If I turn it off and restart it instantly, it will fire right up. However, if it sits for 2-3 minutes, it will take 3-4 longer then average starts to get it going. I tried backing out the low speed screws about 1/8 turn, then 1/4 turn and that made for a rough idle. Also, I tried increasing the tension on the throddle cable to get the idle up a bit. I've not changed the idle stop screw ever, nor sync'd the carbs. It's running sooooo much better than before this rebuild(throughout the entire throddle range), except for the hard starts that I did not have before. Any suggestions before I pull the carbs off again and add a primer kit? Also, having not ever audibly heard a lean or rich fuel condition myself, I'm having a hard time distinguishing the two. Here's a picture of the new plugs that I ran yesterday for about 3 hours, maybe too long to tell by their looks, but any ideas as to too rich or lean? Many, many thanks in advance!!

    Jerry

  • #2
    Re: 96 SPX After Carb Rebuild

    What picture?

    Your story has the high speed and low speed advice for the adjustments backwards. I would not have said "to get rid of an accelleration bog, back out the high speed adjusters".
    That would make an accelleration bog even worse.

    I would have said, "If it hesitates upon accelleration, back out the LOW speed adjusters".

    A bog is the opposite of a hesitation. So if it bogs, you would be turning the adjuster in, not out.

    To raise the idle speed, you need to adjust the idle speed adjuster screw, not tighten the throttle cable.

    If your starting problem persists, then you may need to raise the pop off pressure to around 40 psi.

    My guess is that you do not need a primer, because the hard starting problem is because it is too rich to get it started after parking it for a few minutes when allready warmed up. To test my theory, raise the rear of the hull from the water to expose the exhaust outlet and then see if it starts easier. If so, it is too rich to start easily when the exhaust is underwater and creating backpressure on the exhaust system.

    If I am correct. You can solve this problem by either leaning out the mixture, and/or changing the springs in the carbs to the next highest rated spring.

    I would like to see those sparkplug pictures too.
    Bill O'Neal <br>
    WCM
    <a href="http://www.watercraftmagic.com"

    Comment


    • #3
      Re: 96 SPX After Carb Rebuild

      Bill, you're right, I did have it backwards from what you said on an earlier post. With the low speed screws set at 1 1/4 and the high speed set at zero there was a hesitation at around 25% throddle that would take about 1-2 seconds to overcome then it would take off. When I opened up the high speed screws a little bit, it over came this problem and entire throddle range ran smoothly with a much sharper response then it had ever had before this rebuild. I will definitely try your suggestion about lifting the back end and seeing if it changes anything. When I got it home for a flush, it did start up considerably easier then did in the water. Here's a picture of the plugs with about 3 hours on them, I'm going to use new plugs again when I go out and I'll post pics of those as well. Also, I gapped them against the ones that a previous shop had installed, but to be sure, what is the correct gap for a 717? As always, thanks! P.S.- any chance I could talk you into opening a shop in Dallas, Tx????
      Attached Files

      Comment


      • #4
        Re: 96 SPX After Carb Rebuild

        Ok, way too rich!

        Try this, open the low speed adjusters to 1 3/4 turns out. Close the high speed adjusters to zero turns out.

        Install new sparkplugs.
        Bill O'Neal <br>
        WCM
        <a href="http://www.watercraftmagic.com"

        Comment


        • #5
          Re: 96 SPX After Carb Rebuild

          Bill, finally got a chance to take it out again today and try your advice. As you suggested, I turned the lows out to 1 3/4 and the highs to 0. That did improve the hard starting (used to take 4 hard tries) now it fires up pretty well on the second attempt. With the highs set to 0 it had some hesitation getting up and going past 50%. I then turned the highs out in 1/4 increments and it ended up running very well with the highs at 1/2 turn out. So, now it's running great, starting considerably easier, but rarely on the first attempt. It was choppy today so I was not able to run it for any real distance at open throddle to check the coloring of the plugs as suggested. Once I had it running and starting(just about) where I wanted it, I put in new plugs and ran it to check the coloring. However, the plugs in the picture were run for 11 minutes at about 50% throddle. They look waaaaay lean, unless that was not enough time on them to indicate the mixture. Would you expect the plugs to look like this with a pop off at 30 PSI, Lows at 1 3/4, and highs at 1/2 turn? I'm starting to think that I've deviating too much from the stock settings as a result of having that pop off set too low. Do you think that changing the pop off to around 40 and taking another go at it would solve the problem. Just really afraid of that four letter word, lean.... Thanks!
          Attached Files

          Comment


          • #6
            Re: 96 SPX After Carb Rebuild

            Just curious....whose carb kits did you use? OEM Mikuni, or SBT?

            Comment


            • #7
              Re: 96 SPX After Carb Rebuild

              They're from Gasket Technology. I almost bought the Mikuni set, but was convinced that these were just as good.

              Comment


              • #8
                Re: 96 SPX After Carb Rebuild

                Raising the pop off may help the starting, but certainly has nothing to do with making it richer. Three things make it richer above idle speeds, restriction ( air filters), high and low speed adjusters, and jet sizes.

                We do not do sparkplug checks at 50% throttle. It is a waste of time.

                A normal and natural fuel curve is rich at idle and rich at wot, and leaner everwhere in-between.
                Although the porclean looks white and lean, nothing else on those sparkplugs looks lean one bit.

                Get some running time on the sparkplugs and then do your plug checks at wot, pull the tether, coast to a stop, check the plugs.
                Bill O'Neal <br>
                WCM
                <a href="http://www.watercraftmagic.com"

                Comment


                • #9
                  Re: 96 SPX After Carb Rebuild

                  Bill,
                  You were absolutely right on the money about raising the pop off pressure from 30 PSI up to 40 PSI to solve the hard and hot starting issue! As you said, there was no need for the primer kit, now it starts on the first try every time. I've got the low's out to 1 3/8 and the highs out to just under 1/2 a turn. It's running very well without a hesitation of any kind throughout the entire throddle range. I did the high speed run for the plug test, killing the engine at WOT. Unfortunately, my exhaust coupling broke apart at 12 minutes into the test so I wasn't able to run to the suggested 15. That's another story, but I think I've finally got that solved. What do you think about these plugs, as far as being lean? Thanks again!

                  Jerry
                  Attached Files

                  Comment


                  • #10
                    Re: 96 SPX After Carb Rebuild

                    dundeels, i'd say youve got the carb rebuild down to a science. nice job! was this your first? i've got a 95 spx with mikuni duals that need to be done and i'm a little scared to do them. it runs good but after sitting for a few days starting can be a bitch, and it likes to load up after idling through the no wake zone. were there a lot of special tools to buy? where'd you get the pressure tester? i've checked out the videos here and it seems pretty straight forward. still makes me nervous though. anyway, nice job!

                    Comment


                    • #11
                      Re: 96 SPX After Carb Rebuild

                      One thing that I am seeing that is consistent in all of your photos.....
                      None of the crush washers on your spark plugs have been "crushed" this indicates that the plugs have not been properly torqued. The specs are 17 foot-pounds or 1/2 to 2/3 of a turn after the crush washer touches the cylinder head.

                      This quote is directly from NGK:

                      "Torque is one of the most critical aspects of spark plug installation. Torque directly affects the spark plugs' ability to transfer heat out of the combustion chamber. A spark plug that is under-torqued will not be fully seated on the cylinder head, hence heat transfer will be slowed. This will tend to elevate combustion chamber temperatures to unsafe levels, and pre-ignition and detonation will usually follow. Serious engine damage is not far behind.

                      An over-torqued spark plug can suffer from severe stress to the Metal Shell which in turn can distort the spark plug's inner gas seals or even cause a hairline fracture to the spark plug's insulator...in either case, heat transfer can again be slowed and the above mentioned conditions can occur."
                      John Kubiak
                      Powersports Technical Training Professional
                      Las Vegas, Nevada
                      Sea-Doo Tech 13736
                      PWC Tech since 1988 (22 years)
                      PowerSports since 1976 (34 years)
                      NEVER BUY TIRES AT A "BLOW-OUT" SALE
                      Please do not use Private Messaging, use the forums.

                      Comment


                      • #12
                        Re: 96 SPX After Carb Rebuild

                        LV,
                        I'd been putting off doing those carbs for over a year. I was also concerned that the rebuild of the carbs was way over my head because a lot of my friends told me not to even try it. I'd never worked on a carb before trying this, but because I knew that I could ask my questions to Bill and the other great people here, I decided to go for it. If it weren't for their help, this and many other repair jobs would have resulted in my ski living at the dealer. Seriously, I can't say enough about all the great help and can't send enough people to this site. As for the tools required, the pop off tester was definitely a must have for my situation. Should have bought it from Bill's shop, as I will be buying all my parts from him in the future. Many people suggested an impact scredriver to remove some internal screws in the carbs, but I didn't need it(almost did). Also, if you go to Mikuni's website, there's a GREAT 22 page technical manual on the SBN's that was very helpful.
                        John,
                        Thanks for the heads up about the torque on the plugs!!

                        Comment


                        • #13
                          Re: 96 SPX After Carb Rebuild

                          John and Bill you guys rock! Your advise is spot on!

                          Thanks, as once again I have learned something new from both yours advise.

                          Comment


                          • #14
                            Re: 96 SPX After Carb Rebuild

                            dundeels,
                            Your plugs look good, tuned to go fast.

                            They are not as brown yet as they will get with more time on them, but that is the way I like to see them.
                            Notice the light tan coloring on the porclean. Notice the steel rim at the bottom of the plug, it is wet, which is good because it would be dry if the plugs were too hot or the motor was lean and detonating.

                            Gooid job. Glad to be of help.
                            Bill O'Neal <br>
                            WCM
                            <a href="http://www.watercraftmagic.com"

                            Comment

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