Firestone 1950 5hp Spark Plugs

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  • May 23, 2015 at 11:53 pm #1587
    Buccaneer
    Participant

      US Member

      Can anyone tell me the original spark plugs for my 50 Firestone 5hp?
      The oldest spark plug chart I have only goes back to 1955,
      and I don’t find that information in the Scott manual either.
      Thanks!

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      May 24, 2015 at 12:10 am #16743
      Mumbles
      Participant

        The book sez, Champion H-10J set at .035".

        May 24, 2015 at 1:46 am #16758
        Buccaneer
        Participant

          US Member

          Thanks Mumbles, I’ll see if I can find the modern equivelent.

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          May 24, 2015 at 3:14 am #16766
          jnjvan
          Participant

            US Member

            H-10C are still readily available.

            John Van

            May 24, 2015 at 3:15 am #16767
            jnjvan
            Participant

              US Member

              H-10C are still readily available. That’s what I use.

              John Van

              May 24, 2015 at 1:14 pm #16783
              Buccaneer
              Participant

                US Member

                Good to hear about the plugs being available John.
                Not sure what the difference is / was on the C vs. J suffixes,
                but probably minor.
                Thanks!

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                May 24, 2015 at 2:11 pm #16784
                Mumbles
                Participant

                  The C plugs have the ground electrode extend all the way across the center electrode while the older style J plug ground electrode extends halfway across the centre electrode. This gap design requires less firing voltage at high RPM and also protects from ingested particles and carbon deposits wedging between the gap and shorting out the plug.

                  May 24, 2015 at 3:37 pm #16787
                  Buccaneer
                  Participant

                    US Member

                    My little 80 Yamaha motorcycle back in the 70’s could have used
                    a "J" plug……. always getting carbon chunks stuck in the plug.
                    Sometimes it would go "sputter, sputter, sputter……. BANG!",
                    and I’d be on my way again, but usually I’d be cleaning the plug along
                    the road to get home.
                    I believe Frank? mentions filing plugs to turn them into "J’s".
                    Thanks again Mumbles!

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                    May 24, 2015 at 3:39 pm #16788
                    jeff-register
                    Participant

                      US Member

                      Mumbles & Buc,
                      I am looking forward to getting a 10hp Firestone! Not here yet but soon. A 7.5 Firestone was my first motor & still own it. The ten will be a wonderful addition & enjoy it. Mine is a 1952 I believe. I’ll fix it up real nice to run all the time. Enjoy your motor too. They had Mercury in their sites as they were fast too. I won’t abuse it but up on plane & a little more for fun!!!

                      May 24, 2015 at 9:16 pm #16796
                      Buccaneer
                      Participant

                        US Member

                        Jeff, the 10 hp Firestone sounds sweet. How does the 7.5 shift?
                        I’m already worried about my 5 hp. It definitely won’t shift "not running",
                        but hope it shifts when it is running!

                        Prepare to be boarded!

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