Hi everyone,

I have just got a new piston and ring for my ST G90, and my question is how do I install the ring without breaking it?

Also, is there any specific place the ring goes on the piston? I see by the ring gap is a little notch, and I'm wondering if that notch fits onto a little tab inside the piston gap?

Thanks,

Stefan

There is a pin that you can see the top off on the top of the piston near the edge. The gap of the ring goes where this pin is. You first ease the ring into the cylinder and push it into the cylinder a short distance to observe the ring gap. Does it have a small gap?

Then remove the ring and set it on top of the piston with the gap at the position of the pin. Slide ring gap edge over the side of the piston. Start one side of the gap in the ring adjacent to the pin in the ring grove. The ring will be slightly spiraled. Feed the ring into the groove going all the way around. Again, make sure your gap is at the pin.

Enjoy,

Jim

The rings are usually considerably more flexible when new as apposed to when they have been running in the engine for a while, they become hard from the repeated heating and cooling cycles. So as long as you are careful putting on a new ring shouldn't be to much trouble.

Beware,
The old type supertigre ring used to have a small notch on one side of the ring gap. That is where the locator pin goes that can be seen from the piston top. In that case, it matters very much which side of the ring is up, or the ring ends will catch in the ports.
Hold on to the old ring, so you can check which side was down (the gleaming side), and fit the new ring in the same orientation.
You can bend open the ring by placing the (short) thumb nails in the ring gap and supporting the ring at 1/3rd circumference intervals. Have the piston supported by using two wood blocks in a vice that clamp the rod, so the piston skirt sits on top of the wood. Now when you bend open the ring, just do it wide enough so the ring can be slid into place. The thumbs pull, whilst the index fingers push the ring. Easier done, than said.
The hard part follows next. That is keeping the ring notch aligned with the pin while fitting the cylinder from above. Don't force anything. Easy does it.