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787 Rotax Motor Rebuilt the top end but motor wont start

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  • 787 Rotax Motor Rebuilt the top end but motor wont start

    I recently (and stupidily) ran my 1800 Challenger without oil. I totally wore out the pistons and it's rings on one of the engines (its a twin). Anyway I bought a piston rebuild kit and installed everything as the shop manual states (btw I have never did this before). After I tighten everything to torque specs and plugged in all the hoses I crank the engine and it wont start!! Very frustrating after working for days on it. The engine turns , the spark plugs have sparks, the fuel is good (since the other engine works) battery is ok. I didnt check the compression becuase I dont have one of those testers ( will buy one ). After trying to crank it for a while I shot starter fluid and that didnt work either. A couple of times it started but immediately died. Not sure what the problem is. BTW when i took the spark plugs off to check them. I noticed the oil was a grayish color. One more so than the other. Any suggestions. I need help on this because I can't afford a sea doo dealer mechanic!!!

  • #2
    Re: 787 Rotax Motor Rebuilt the top end but motor wont start

    do not use starting fluid . if you tore up your pistons with no oil iam sure the crank is not feeling to well . did you check it ? also did you check the rotory valve ? if not check it now . if the plugs are gray and fould it will not start the gray is dirt from the rebuild , you need to confirm the rotory valve is in time and spinning and that you have good compression , if so then put a new set of spark plugs in .
    PRIDE IN SERVICE<br /> <img src="http://www.sbtontheweb.com/images/forposts/4609/1.jpg" alt=" - " />

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    • #3
      Re: 787 Rotax Motor Rebuilt the top end but motor wont start

      Check your fuel lines to be sure they are not reversed and also make sure you connected the pulse line to the cases and carbureators.
      Bill O'Neal <br>
      WCM
      <a href="http://www.watercraftmagic.com"

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      • #4
        Re: 787 Rotax Motor Rebuilt the top end but motor wont start

        Make sure you fuel selector is set to ON. A lot of these boats have one selector for each engine.
        Dan Solie -
        04 RXP (the "Instigator")
        94 xp (freestyle mods)
        95 xp (faster than the 94)
        JS550 (the toothpick & the loaner)

        For FREE Seadoo Manuals - Click HERE!!!!

        http://www.tripleateam.com/water/v/U...ery/Dan-Solie/

        **** Please do not PM me. I don't do PM's.... Please post your question on the correct forum so that all can see and learn. Thanks! ****

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        • #5
          Re: 787 Rotax Motor Rebuilt the top end but motor wont start

          When I checked my pistons and saw that I tore them up I also checked the crankcase by checking if I ran it dry. I opened the plug on the side and it still had oil in there also it turned fine so I assumed the crankcase was fine. The rotary is indeed spinning. The spark plugs are brand new.

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          • #6
            Re: 787 Rotax Motor Rebuilt the top end but motor wont start

            You didn't inspect anything. You needed to break it down and properly inspect every inch if the crank and bearings.
            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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            • #7
              Re: 787 Rotax Motor Rebuilt the top end but motor wont start

              In your first post you didnt mention doing anything to the cylinders! did you ? Do a compression test and let us know the numbers.

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              • #8
                Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                I rehoned the cylinders gave it a nice crosshatch pattern. The ring end gap is .030in ( I know it is a little big but according to seadoo the gap can be up to .039in on a wear limit should work I guess?? ) I will do a compression test shortly will give you my numbers.

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                • #9
                  Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                  I checked the compression it was about 150psi on both cylinders. Anything else I can do before I break it down to the crankshaft?

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                  • #10
                    Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                    Try new plugs....Check all the fule hoses again, and pulse line...

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                    • #11
                      Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                      Dumb question. Whats a pulse line?

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                      • #12
                        Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                        The line between the fuel pump and case.
                        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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                        • #13
                          Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                          Short fuel hose that runs from the engine crankcase to the carburator with the fuel pump(Says pulse) on it...Did you remove the carbs or rotary valve cover during your rebuild?

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                          • #14
                            Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                            Yes I checked that. I connected it.

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                            • #15
                              Re: 787 Rotax Motor Rebuilt the top end but motor wont start

                              I did remove the carbs and rotary cover during the rebuild.

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