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Has anyone made a small bore piston ring expander?

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  • Has anyone made a small bore piston ring expander?

    Has anyone made a piston ring expander for rings in a small bore engine around 1.125" diameter. I imagine it would be very easy to break a ring trying to expand it enough to get over the piston on such a small bore.
    Larry

  • #2
    Originally posted by Cuttings View Post
    I imagine it would be very easy to break a ring
    Not in my experience, I mean there small so you could break them if you tried, but I haven't yet
    .

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    • #3
      I just put a "BIG BORE KIT" on a 49cc engine. I put the rings on the piston by hand (no tools). While I was a bit nervous, it was easy to put them on by spreading with my thumb nails. That engine has so much compression it's hard to keep from lifting the whole mini-cycle when starting.

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      • #4
        I've put in hundred of rings into chainsaws, weed eaters etc. Found expanders not useful at all; I just use my fingers.

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        • #5
          Originally posted by lakeside53 View Post
          I've put in hundred of rings into chainsaws, weed eaters etc. Found expanders not useful at all; I just use my fingers.
          Did some of if any come ring-less? Lake?





          Solly, For a 1" bore or smaller I like my modified HF handful for couple buck tweezers and grind as needed. They come sprung or clamped.

          I had to practice, but they used to give you a pack of various sizes and shapes so I would modify them. You can even serrate the smallest of tips as long as you don't soften the tip during grinding. Not sure if it helps. JR

          P.S.

          Oh, I should have added. For a small gap ring I serrate the outside of a tweezers. Then grasp the ring, ever-so slightly and land it.

          Here are some tools that are easily modified and wont take more than ten bucks and a small box of nails. Amazing control cause its a leverage tool, nice and slow. JR



          Last edited by JRouche; 07-25-2019, 12:09 AM.
          My old yahoo group. Bridgeport Mill Group

          https://groups.yahoo.com/neo/groups/...port_mill/info

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          • #6
            Originally posted by CCWKen View Post
            I just put a "BIG BORE KIT" on a 49cc engine. I put the rings on the piston by hand (no tools). While I was a bit nervous, it was easy to put them on by spreading with my thumb nails. That engine has so much compression it's hard to keep from lifting the whole mini-cycle when starting.
            Cast iron ring? So scary with those cause if you snap it you are SOL again. JR
            My old yahoo group. Bridgeport Mill Group

            https://groups.yahoo.com/neo/groups/...port_mill/info

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            • #7
              Originally posted by JRouche View Post
              Cast iron ring? So scary with those cause if you snap it you are SOL again. JR
              Is there anything else? Inserting the piston into the cylinder was even scarier. The piston had pins the rings had to match with half-moons on the ends. Get the rings misaligned and they will probably break when pushed into the cylinder. Or just stop and chink-up the cylinder.

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              • #8
                In over 50 years as a mechanic I’ve put on thousands of piston rings with just my fingers and don’t think I’ve ever broken one. Just expand them enough to slip over the outside diameter. You can fit one end into the groove and carefully rotate the ring around & into it. If it needs to go down to the next groove, do the same process again.
                Also, many rings have an orientation as to which side must be facing up (toward the top of the piston) and an effort must be taken to observe this. Read the instruction sheet carefully. In other word, imagine the ring in a heads or tails situation. The rings are packaged which ring goes in which groove. Usually there is a dot on the ring which designates that it (the dot) faces the top of the piston. No marking would mean they can go either way. That is unless there is a chamfer on the inner diameter of the ring indicating that the chamfer faces up.

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                • #9
                  Originally posted by Mcgyver View Post
                  Not in my experience, I mean there small so you could break them if you tried, but I haven't yet
                  Most small engine piston rings are something close to spring steel nowadays(or last 40 years), almost impossible to break even if you wanted.
                  Same with car engines, either some sort of spring steel relative or at least nodular cast iron in almost any engine designed within last 50 years.
                  Last edited by MattiJ; 07-25-2019, 11:10 AM.

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                  • #10
                    Originally posted by MattiJ View Post
                    Most small engine piston rings are something close to spring steel nowadays(or last 40 years), almost impossible to break even if you wanted.
                    Same with car engines, either some sort of spring steel relative or at least nodular cast iron in almost any engine designed within last 50 years.
                    my comment was based on cast iron model engine rings, more fragile, yet they don't seem to break. They sort of go on almost with a bit of a twist - i.e. they flat surface doesn't stay in the same plane. That I think makes it easier than if you just tried to expand them outward enough in the same plane. I'd say a device to expand them would have to have similar motion or it would be more apt to break them
                    .

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                    • #11
                      Thanks for all the comments guys. Like Robg I have installed a countless number of rings on much larger engines where you had to have an expander because the rings where so strong you would probably rip off some finger nails trying to do it by hand. I have put smaller ones on by hand without breaking any as far as I can remember. These ring are so small they won't want to expand very much. I thought some kind of small expander would be handy. Once the rings arrive and I have machined the pistons I will see what it looks like. I have an idea about a holder for the rings that I could use a small pair of snap ring pliers in to carefully expand the rings if needed. We will see how it goes.
                      Larry

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                      • #12
                        Originally posted by Robg View Post
                        You can fit one end into the groove and carefully rotate the ring around & into it.
                        This. I've never bothered to make a ring expander because doing it by hand was easy on everything from a big block Chevy V8 on down to chainsaw motors. Some of those definitely use a cast iron top ring; I've never broken one installing by hand. The idea is to work the ring around the piston into the groove rather than trying to expand it to slip over in one go by hand.

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                        • #13
                          You might try putting either a triangular Exacto blade or a narrow Olfa blade down the inside of the ring and slide it through the split until it is flush on the inside of the ring. This should expand the ring about fifteen or twenty thou.
                          Duffy, Gatineau, Quebec

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                          • #14
                            Originally posted by Duffy View Post
                            You might try putting either a triangular Exacto blade or a narrow Olfa blade down the inside of the ring and slide it through the split until it is flush on the inside of the ring. This should expand the ring about fifteen or twenty thou.
                            Or a leaf from a feeler gage.

                            -js
                            There are no stupid questions. But there are lots of stupid answers. This is the internet.

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                            • #15
                              If you have a wide, cast iron, one-piece oil ring (old engines), warm the ring up first, this helps prevent breakage.

                              And you can't fit these as the other posters suggest, they can't be "wound on".

                              Personally I prefer to use my thumb nails rather than a ring expander...

                              Alot of books/manuals used to show several feeler gauges being used as sliders for fitting rings. I have never had to do this, but it might help.

                              The

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