Announcement

Collapse
No announcement yet.

poor performance

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • poor performance

    I recently installed a SBT motor in my 1994 SL 750. The new motor doesn't have as much power as previous one had. The ski tops out at about 40 mph and the rpm tops out at 5200-5400. The machine doesn't bog it just lacks power and responsiveness.

  • #2
    Take a good compression gauge and check the engine - you shoul dhave around 120 psi on each cylinder.

    Beyond that, check your reeds, make sure you are using the right plugs, the carbs are clean and functioning...

    Comment


    • #3
      I checked my compression and it reads around 95 psi in all cylinders. Should I hone the cylinders and replace the rings?

      Comment


      • #4
        No, you should get an accurate gauge.

        Comment


        • #5
          I checked the guage on a slx and the compression is around 120 in all cylinders, so it for sure works.

          Comment


          • #6
            Give me your serial number - it's on the engine stamped on the front of the heads - and printed in your owners manual. I will lookup what that block left here testing at.

            Comment


            • #7
              Make sure your holding the throttle open while checking compression. Not sure it can effect reading as much as 25psi thou...

              Tim

              Comment


              • #8
                How much running time do you have on the engine? What elevation are you! The best way to check for a bad seal on the rings would be to do a leak down test Not a compression test. Did you run it without any premix oil in the fuel. You can "wash the cylinders" and destroy the rings in a matter of seconds if the cylinders are run dry. I would agree that 95lbs seems a litlle low but A compression test is not always the answer. I suggest that you call SBT and ask them to help you figure out what could be wrong. I am sure they will address your problem without delay

                Comment


                • #9
                  Brian,
                  My SBT serial number is 13038.

                  Comment


                  • #10
                    That particular block blew 125 here on the test stand before it shipped.

                    Comment


                    • #11
                      battery at full charge, plugs loose in the other 2 cyls, full throtle open, crank several rotations until the gauge isn't changing wildly.

                      My ski only was doing 47 - 48 on the sbt motor [not completely new, but previous owner has 10hrs on it] MAYBE on a good day it'd click off 50.

                      pulled the jugs for a group k rec port, had a fresh set of salvaged heads for group k's pump gas mods, replaced +1mm sbt rings for good measure... few carb jetting changes and it woke this ski up like a hamster on fire.

                      Actual compression after a season of hard abuse is around 140-150psi.

                      -Skexies

                      Comment


                      • #12
                        What do you think I should do. The motor is still under warranty, will sbt fix the motor??
                        Also I am looking at purchasing a 1997 Polaris SL 900. What are your thoughts on this particular model. Are they reliable?

                        Thanks

                        Comment


                        • #13
                          I *highly* suggest you verify your compression is actually low - get a shop to test it for you, make sure you're doing everything right - it was fine when it left, and the odds of all your cylinders being equally low from damage are slim to none. We can certainly take it back for warranty service, but if we get it back here and it looks fine, you will just be out shipping and time for nothing.

                          You could veru easily have something else wrong with the ski causing your problems.

                          If you wish to send it back for a look, call in and talk to Julie.

                          Comment

                          Working...
                          X