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Eratic Spark On Both Cylinders

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  • #16
    You normaly do a plug reading but if you can't keep it running it may be hard to do so. If you pull the plugs and they are dry and it won't take throttle if sounds like it is starving for fuel. If you can;t get the carbs right yourself you can take them to a shop or replace them. I have a set if you need them $200
    Providing mobile JetSki service to the Charlotte / Lake Wylie area.

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    • #17
      It does not matter what the piston says on the top you have to mesure each one and set the clearence from that not by what the piston says. Each piston will be a different size bran new.
      Providing mobile JetSki service to the Charlotte / Lake Wylie area.

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      • #18
        According to my Daytona manual for optimum conditions the cylinder should be 0.15 mm larger than the piston in diameter to allow for clearance. Is there a cylinder size above the piston that has been proven to crack or break piston skirts from looseness (ie 0.4, 0.5, etc. mm). I have a co-worker that swears 0.3 over will not yield any piston damage.

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        • #19
          You are confusing metric and american standards. 0.15mm = 0.006" which is correct clearance. 0.008" is about your max limit. I think your co-worker said 0.003" which is the minumum, and even I won't recommend under 0.0045".

          Everytime you match new pistons with a cylinder, the cylinder NEEDS to be at least checked, and the clearance set by fine honing. If the clearance is already too great, you must go to the next oversize. You can NOT measure once it's assembled.
          SBT Tech Support is here to help with your problems.
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          Please do not use Private Messaging for Tech Support, use the forums.

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          • #20
            So you are saying that even at 0.3 mm (0.012 inches) or 0.4 mm (0.016 inches) piston damage will definitely occur??

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            • #21
              Yes - piston slap and cracked pistons, along with lowered compression and horrible blow-by.
              SBT Tech Support is here to help with your problems.
              We try to answer each question quickly and accurately.
              Please do not use Private Messaging for Tech Support, use the forums.

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              • #22
                OK. Tore it down and removed both pistons and ordered kit with next size 0.012 pistons and rings. Also ordered new bearings. Honed cylinders and they measure 76.0 mm. If they have to be bored to fit pistons I have someone who can take care of it. My question is once I get it back together what is the safest way to test it and not burn another piston? Last time it burned in about 3 minutes. I have totally disassembled carbs and cleaned and there is no blockage in either carb. I was thinking of setting the High Speed jet at 1&1/4 turn (1 is recomended) to start with just to be safe.

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                • #23
                  I would even take it to 1 3/4 to be really safe as far as jetting - if you have an air leak or ignition issue however, the carb settings won't save you. Make sure you pressure check the block before putting it back in.
                  SBT Tech Support is here to help with your problems.
                  We try to answer each question quickly and accurately.
                  Please do not use Private Messaging for Tech Support, use the forums.

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                  • #24
                    OK. Received the +0.012 top end kit. Honed cylinders. Both are 0.006" larger than pistons. Got it put back together tonight. Pressure checked engine at 8 psi with no loss over 10 minutes. Started it for about 30 to 40 seconds just to see if it would run. It still seemed to miss and not run very well. Did'nt go to the lake today, too exhausted. Have High Speed set at 1 and 3/4 turns out and low speed set at 1 and 1/4 turns out. Will probably take it to the water tomorrow. I read the break-in procedure. Any other advice on tuning the carbs if it does not run very well. Plugs were in pretty bad shape but I will get new ones tomorrow. Didn't have any spares. Oh, one question. When I had it running before and pulled the fuel return line loose very little fuel was being returned to the tank. Today I checked both Super BN's before re-assembly and of course the Mag side has no return restrictor but on the PTO side there is a restrictor and the hole is about the diameter of a pin. It actually looks like it was mis-formed or not drilled completely. Is this normal??

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                    • #25
                      there is a restrictor in the line but I am not sure of the size
                      SBT Tech Support is here to help with your problems.
                      We try to answer each question quickly and accurately.
                      Please do not use Private Messaging for Tech Support, use the forums.

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                      • #26
                        Took it out for the first 30 minutes of Break-in. Added oil for 32:1 mix approximately. Idled great. Hit the throttle briefly at end of ride for about 1 sec and it bogged badly and missed for about 4 seconds and then attempted to take off. I stopped before RPM's went too high since Break-In not complete. Mag side plug was gray and dry and Pto side plug was glossy black with oil. Tops of both pistons still shiney with lettering clearly visible. Suspect carbs but do not know where to start. Compression now 135 and 137. Any further advise?? Does anyone know the approximate size of the hole in the restrictor in the PTO side Carb? Should the MAG side Carb have a restrictor?

                        [ September 18, 2003, 07:04 AM: Message edited by: Shark1 ]

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                        • #27
                          Order some new carbs from Arctic Cat. I just had to do it with my 96' Daytona and it is worth every penny. I put in a Rebuilt SBT engine, new carbs, and new jet pump and it ran great.
                          Providing mobile JetSki service to the Charlotte / Lake Wylie area.

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                          • #28
                            What did all that cost you? I took mine out for the 0 to 50% throttle 30 minute break-in ride today and after about 20 minutes it started running worse. Came home and checked compression and PTO down to 60 PSI. I've already $75 and $100 myself into about a total of $400 so far and now it's wasted. I'm thinking of taking the SBT route before I get in any deeper. There's something going on with this Engine\Carb system that I am missing and I am basically tired of fooling with it. If I put in an SBT engine and new carbs there is really no other problems that could arise is there? After all, I have already swapped stators and CDI's and know they are good.

                            [ September 19, 2003, 06:31 AM: Message edited by: Shark1 ]

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                            • #29
                              Most engine damage will be caused by either a defective oil injection system, crank seal leaks or carb broblems. I have never seen the electrical system cause engine damage.
                              Providing mobile JetSki service to the Charlotte / Lake Wylie area.

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