Question about replacing rings in my G1

[sontag1]

I have a 1982 G1 (J17). A few months ago I went through the top end (gaskets / rings), replaced my drive belt, both crank shaft seals and it went fine. I honed the cylinder very lightly while I had the jug off. I did not measure it because I really did hone it very lightly. Cart was running great for a short while, then it just stopped. It would crank fine, but no combustion. I got it back to the house and there it sat until last weekend. I pulled the jug and there was my problem. I had about 2" of the top ring left. Bottom ring was fine, but most of the top ring was gone! I guess it went into the muffler??? I had a couple of small dings in the top of my piston and a nice chip out of the front of the piston. The chip just went into the first ring groove. The cylinder walls showed no damage. No damage on the underside of the head either. I figured if I popped a couple of new rings into the piston, it would still hold good compression. I got my parts this week, and I installed the rings today. It was supposed to be a stock set of rings (no oversize). So I slid them down into my cylinder and the end ring gap was way out of specs. My SM states .2 mm minimum and .4 mm maximum. My end ring gap was between 1mm and 2mm. I installed them anyway and offset them 180 degrees. I just popped them in and got it all put back together and fired it up. The results were underwhelming to say the least. I will check compression tomorrow. Do I need to just suck it up and buy a new piston with rings???
Please

[1989Marathon]

Can you post a pic of the chip in the piston?
After you honed the jug, did you make sure there were no sharp edges on the port openings?

[sontag1]

I can post a picture of the chip tomorrow after church.

All of the ports looked good (no sharp edges).

EDIT:
Both of my rings were marked with an "H".
My SM states that the top ring will be marked "RN" and the bottom ring will be marked "R"

Does this matter??? Are the two rings different sizes??? Maybe that is why my end ring gap was way off. I ordered my rings off of FleaBay. The part # was correct and they looked to be the same size as the old ring.

[1989Marathon]

I'd be afraid to spend money on new rings and piston unless I knew what happened. I would measure the cylinder bore and make sure it is within spec.
Also, make sure the rings are installed correctly.

[sontag1]

I installed them as per the instructions in the SM. The only issue is that the little "nub" in the top ring groove (that prevents the rings from spinning) is flat. When the ring is compressed in the top groove, it can spin. The bottom groove is fine. The little "nub" prevents the ring from spinning while it is compressed.

I will pull the piston tomorrow and post pictures.


I only have a set of regular calipers. I can get a good measurement at the top and bottom of the cylinder. As long as the sides are parallel I should then have a good measurement. Is that correct?

[1989Marathon]

You said the top ring was gone and the bottom ring was fine. If the pin inside the top ring groove is not working properly, I would think that's why the top ring went bad. If the end of the rings are allowed to rotate into the port windows, they won't last very long. I think it might be better to get a new piston and ring set.

[sontag1]

That makes sense!

I did not even consider the ring ends rotating into the port windows. I have been wracking my brain trying to figure out how the ring failed and shattered.

I have found a new piston with rings at LVS sales for $35.

I will double check the measurement on the bore and piston tomorrow before I order.

Thanks for the help

[1989Marathon]

Good luck with it. Keep us posted please.

[sontag1]

I will post pics of the wonky piston when I pull it. I am sure it was original to the cart. Really, that is not too bad for a part that is 30ish years old.

[sontag1]

Yesterday, I drove the cart about 200 yards. When I pulled the jug today, the top ring was gone again. I was not too surprised. I am just glad it did not mess anything up other than the piston. Here are some pictures of the damaged piston. I circled the dings in the face/top of the piston and outlined the indicator arrow to show the front of the piston. The last picture shows the two chips from the bottom of the piston. Who knows where they went???