Ok I am changing a piston on an OS91 and the new piston has a ring installed. How do I get the ring in the engine sleeve. It's almost impossible

If it is a two stroke OS 91 the piston has a pin in the ring groove

The ring must be aligned with this pin or youw ill never get the assembly in the sleeve,

The ring gap goes where the pin is



The ring gap must never come past a port or you may as well throw it all away

Engine sleeve, I guess you mean liner? If so, Take out the liner, replace ring on piston, replace piston and then instert liner over piston and slide down.
When you remove the liner you'll notice that it has a tapered bottom edge that slides easliy over the ring.

If you can't remove the liner but have managed to replace the ring, you can get some strong fishing line or pull-pull cable, slide piston down until the ring rests on the liner and then make a loop out of the trace passing it around the ring.
As you pull on each side, you'll compress the ring and you'll be able to push in the piston using your thumbs.
Fiddly, but it'll get you there.

<pre>An Arrow Stamped Into the Top of the Piston Shows Which Way the Piston Should be Installed. The Arrow Must Point to the Exhaust Port. </pre>

Rings are hard and brittle and will easily break if bent beyond that necessary to ease them into the piston groove. Noting the ring locating pin and arrow on the piston top in the other posts, insert the piston into the sleeve up to the ring. Tighten a cable tie or a hose clamp around the ring, compressing it and allowing, then, the piston/ring to be gently tapped into the sleeve. Tighten the table tie or clamp just enough to compress the ring, but still allow the piston to slide out into the sleeve.