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Rebuilding a rotax 650 - Share your tips!

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  • #1

    Rebuilding a rotax 650 - Share your tips!

    As some of you may remember, I returned to the PWC world last year with a 94 SPX only to have the engine fail on me in less than a month of use, leaving me high and dry with an empty wallet and a long face. Fortunatly, I have rallied and decieded to go ahead and rebuild for this upcoming summer. These things are just too much fun to let sit. So, without further adu, here is my rebuild plan:

    The cylinders will be bored 1mm over (first question: can I go any bigger without compromising reliability? - wiseco sells kits up to 2mm over), wiseco pistons, rings and wrist pins. SBT rebuilt crank(reliability vs. OEM? Quality?), PPG milled stock head, new rotory valve, rebuilt kits for the SBN 38mm carbs (question: I want to rebuild the fuel pump to... is this included in the carb kit since its built in to the carb?) and new needle valves, new plugs (BR9ES for the milled head) and wires, and last but not least a clymer service manual so I know how to put it all together (is this a good service manual?). All told this is going to cost me about $950 when its all said and done.

    Now on to the machine work questions. Ive heard from one person a "special" final hone is needed to work with the Wiseco pistons and rings but I cant see why. Should any reputable machine shop know the proper hone for a PWC engine? I want to know the truth.

    Ive been instructed to tell my machinist to set the pistons up at .005" clearance measured from the skirt of the pistons...not the pin area. What other tips should i give the machinist to assure a quality overbore? I want this done right so I can see a few trouble free years.

    Please tell me if Im leaving anything out, suggestions, tips, recommendations welcome!

    looking forward to a good year on the water!

    Silas
    96 XP - K&N F/As, Accel Ignition, R&D TTs, Intakegrateless, Solas XO
    94 SPX rip (rebuild in progress)
    89 SP rip
    Tags: None
  • #2
    Re: Rebuilding a rotax 650 - Share your tips!

    Silas,
    Call SBT and order 1mm oversized SBT pistons. They are not forged racing pistons and they will outlast the liteweight Wiseco racing pistons and are much more user friendly. You will be glad you do.

    An oem service manual blows away the Clymer manual for accuracy. You can get one off ebay in CD form for about $15.00 or a hard copy from any SD dealership. A very good investment.

    Or for less than $950.00 you could trade motors with SBT and not worry about the building of the motor, plus you get a years' warranty on it.
    Bill O'Neal <br>
    WCM
    <a href="http://www.watercraftmagic.com"

    Comment

    • #3
      Re: Rebuilding a rotax 650 - Share your tips!

      Just buy the SBT motor so you can ride it, it's a little late to start a "rebuild" project now.... :)

      Comment

      • #4
        Re: Rebuilding a rotax 650 - Share your tips!

        I agree with parrothd and Bill buy the motor from SBT and if you need carb kits which will come with the fuel pump side diaphram and everything else except the needle valve (which should be good anyway) included in the kit I have two for 55.00 plus shipping. Most dealers Ive dealt with want 39.95 each. I would do the carbs whether you rebuild or buy SBT.

        Comment

        • #5
          Re: Rebuilding a rotax 650 - Share your tips!

          If I go with an SBT engine the total cost for me to have a running boat will be ~ $960. If I go with my route (with high compression head) it it will cost a little less @ $940. The question becomes, is it worth my time to rebuild myself, save some money or have it done and just plop the new motor in there?

          Another quick question: Is it possible to use a 657X short block and dress it with standard 657 parts (intake, exhaust, etc) and electronics? I may be able to get one cheap, and I want to know if i can just drop it in. I know I wont see any gains, just curious.
          96 XP - K&N F/As, Accel Ignition, R&D TTs, Intakegrateless, Solas XO
          94 SPX rip (rebuild in progress)
          89 SP rip

          Comment

          • #6
            Re: Rebuilding a rotax 650 - Share your tips!

            I think you are out of luck on the 657 vs 657x but the thing you have to think about also is you saved alot of time and got a 1 yr warranty for that 20.00 savings.

            Comment

            • #7
              Re: Rebuilding a rotax 650 - Share your tips!

              All of the bolt-on parts from a 657 will work on a 657X case, no problem.

              I think you would be miles ahead of the game if you bought the engine from SBT.
              Bill O'Neal <br>
              WCM
              <a href="http://www.watercraftmagic.com"

              Comment

              • #8
                Re: Rebuilding a rotax 650 - Share your tips!

                I understand the desire to do the work yourself. Afterall, that way you know it's right...right? And if not, you know who to blame.
                The thing is, SBT has a 1 year (and here's the important point) NO FAULT warranty included in the purchase price with a second year option avaliable with their premium package.
                If they mess up and leave something loose, they replace it.
                If you mess up, they replace it.
                If an oil line vibrates off, they replace it.
                If in 11 1/2 months a crank seal fails, they replace it.

                It's real hard to beat that. I don't know of anyone, anywhere that has a warranty as liberal as SBT. To me, the piece of mind is worth more than $20.
                IMHO it boils down to that Dirty Harry line
                "Ya feelin lucky, punk?" (no offense to you intended)
                Any technology, sufficiently advanced, will appear as magic.

                Comment

                • #9
                  Re: Rebuilding a rotax 650 - Share your tips!

                  Originally posted by Bill O'Neal2
                  All of the bolt-on parts from a 657 will work on a 657X case, no problem.

                  I think you would be miles ahead of the game if you bought the engine from SBT.
                  Thanks for your input. I know the rotary valve timing is different between the two motors (147*on the 657 vs. 153*on the 657X), will this cause any timing problems? Or do I just purchase a 153* rotary valve?

                  Any yes I think I will go with SBT. Im just trying to figure out what is best for me. Who manufactures the pistons used in the SBT engines?

                  Thanks for all the input!
                  96 XP - K&N F/As, Accel Ignition, R&D TTs, Intakegrateless, Solas XO
                  94 SPX rip (rebuild in progress)
                  89 SP rip

                  Comment

                  • #10
                    Re: Rebuilding a rotax 650 - Share your tips!

                    They have their own manufacturer I dont think I have ever seen the name of who does them but I do know that Bill O likes them better than wiseco because of the way they are made vs wiseco pistons he says they last longer. As far as the timing yes you would just buy the different rotary valve and then set the timing. The only thing about SBT is you have to send back what you ordered.

                    Comment

                    • #11
                      Re: Rebuilding a rotax 650 - Share your tips!

                      Originally posted by smithsil
                      Thanks for your input. I know the rotary valve timing is different between the two motors (147*on the 657 vs. 153*on the 657X), will this cause any timing problems? Or do I just purchase a 153* rotary valve?

                      Any yes I think I will go with SBT. Im just trying to figure out what is best for me. Who manufactures the pistons used in the SBT engines?

                      Thanks for all the input!
                      We make our own pistons.

                      There is no such thing as a 153 OEM valve or timing spec. It's a 159deg durration valve, timed to 147. he older engines used a 147deg durration valve timed to 130.
                      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.

                      Comment

                      • #12
                        Re: Rebuilding a rotax 650 - Share your tips!

                        So all I would need to do would be buy a 159* Rotary valve to match the 657X and then time the **** thing. Right?
                        96 XP - K&N F/As, Accel Ignition, R&D TTs, Intakegrateless, Solas XO
                        94 SPX rip (rebuild in progress)
                        89 SP rip

                        Comment

                        • #13
                          Re: Rebuilding a rotax 650 - Share your tips!

                          Right.
                          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.

                          Comment

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