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1983 gs450 cranks & won't start

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    1983 gs450 cranks & won't start

    Rebuilt a 1983 GS450. Was my daily driver last year until I put it away in December.

    Took the winter/spring to go over the bike and rebuild, refurbish, and replace anything and everything that needed it.

    Bike is back together, engine cranks but doesn't start.

    Got spark
    Got fuel (premium too!)
    Got compression

    ... I don't know why she won't fire up.


    #2
    What is the battery voltage before and during the time you are trying to start it?
    Cowboy Up or Quit. - Run Free Lou and Rest in Peace

    1981 GS550T - My First
    1981 GS550L - My Eldest Daughter's - Now Sold
    2007 GSF1250SA Bandit - My touring bike

    Sit tall in the saddle Hold your head up high
    Keep your eyes fixed where the trail meets the sky and live like you ain't afraid to die
    and don't be scared, just enjoy your ride - Chris Ledoux, "The Ride"

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      #3
      Double check that plug wires are on correct plugs.
      Sounds like my bike when I didn’t use petcock prime long enough….make sure “choke” is fully “on” and don’t use any throttle during cranking.
      1981 gs650L

      "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

      Comment


        #4
        Originally posted by cowboyup3371 View Post
        What is the battery voltage before and during the time you are trying to start it?
        13.1v - 12.9v Battery is still strong

        Comment


          #5
          Originally posted by tom203 View Post
          Double check that plug wires are on correct plugs.
          Sounds like my bike when I didn’t use petcock prime long enough….make sure “choke” is fully “on” and don’t use any throttle during cranking.
          All good points, I read elsewhere on this site. Coils are wired properly, petcock set to PRI, and choke is full send.

          Comment


            #6
            First things I checked were

            - grounds
            - battery
            - starter solenoid
            - starter
            - coils
            - spark plugs
            - fuel line/carburetors
            - compression

            Going to test compression again as all the above are solid

            Comment


              #7
              https://flic.kr/p/2mAXtZz Cylinder 1 - Dry compression test

              https://flic.kr/p/2mANCXj Cylinder 2 - Dry compression test

              https://flic.kr/p/2mAWgME Cylinder 1 - Wet compression test

              https://flic.kr/p/2mASUcd Cylinder 2 - Wet compression test

              Looks like I now need new piston rings...

              Comment


                #8
                Originally posted by StarcrossedMoto View Post

                Looks like I now need new piston rings...
                Just an opinion from a non-mechanic, but I'd say that at 115 on both cylinders, you're good. Spec probably says that 120 is the low limit, but I've also read that 100-105 would be the absolute low service limit. Maybe that's different on the twins, I don't know. New rings certainly won't hurt, I just don't know that this is causing the bike to not even cough when you try to start it.
                Rich
                1982 GS 750TZ
                2015 Triumph Tiger 1200

                BikeCliff's / Charging System Sorted / Posting Pics
                Destroy-Rebuild 750T/ Destroy-Rebuild part deux

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                  #9
                  105psi should run fine, and if the ring packs are sticking slightly, they'll usually free up with use.
                  Only worry about new rings if they dip below 100.
                  Heck, I'd only bother once the damn thing simply wouldn't start and a test revealed 70psi or so.
                  ---- Dave

                  Only a dog knows why a motorcyclist sticks his head out of a car window

                  Comment


                    #10
                    1: How did the rings wear out when you weren't riding it?
                    2: did you have the throttle wide open when testing compression?

                    that is to say, the bike you stopped riding last year is the same bike this year, engine wise. So Something Else has changed: aka gummed, rotted, been "refurbished" or "replaced"
                    Last edited by Gorminrider; 10-16-2021, 10:23 AM.

                    Comment


                      #11
                      Originally posted by Grimly View Post
                      105psi should run fine, and if the ring packs are sticking slightly, they'll usually free up with use.
                      Only worry about new rings if they dip below 100.
                      Heck, I'd only bother once the damn thing simply wouldn't start and a test revealed 70psi or so.
                      Originally posted by Rich82GS750TZ View Post
                      Just an opinion from a non-mechanic, but I'd say that at 115 on both cylinders, you're good. Spec probably says that 120 is the low limit, but I've also read that 100-105 would be the absolute low service limit. Maybe that's different on the twins, I don't know. New rings certainly won't hurt, I just don't know that this is causing the bike to not even cough when you try to start it.
                      Hmm...so that should still be enough compression, huh?

                      Comment


                        #12
                        Originally posted by Gorminrider View Post
                        1: How did the rings wear out when you weren't riding it?
                        2: did you have the throttle wide open when testing compression?

                        that is to say, the bike you stopped riding last year is the same bike this year, engine wise. So Something Else has changed: aka gummed, rotted, been "refurbished" or "replaced"
                        You're suggesting that the problem is not my engine but one of the newer components? I guess I was looking at it the other way around: since everything else was tended to, the only thing I didn't replace or touch was the engine, I naturally assume it is the engine at fault here.

                        What else could it be?

                        Comment


                          #13
                          If the bike was ok before you "fixed" or "improved" it, and is not ok after, the obvious conclusion is that something was disturbed in the process.

                          Comment


                            #14
                            Originally posted by Gorminrider View Post
                            If the bike was ok before you "fixed" or "improved" it, and is not ok after, the obvious conclusion is that something was disturbed in the process.
                            The bike already had electrical gremlins and carb issues, plus the tank was rusted, so it all needed to be serviced and replaced or restored.

                            So I know you are putting fixed in quotes, but everything is far better now than it was when I acquired the bike.

                            Comment


                              #15
                              Just saying. "fixed", "improved" happens to me all the time. The last thing I 'fixed" is the first place to start.

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