I'm in the process of trying to change the ring on my Irvine 150. It was real tough getting the connecting rod off the crank pin, but after a bit of prying with a blade screwdriver, it finally came. The old ring was pretty much completely burnt, and came off in chunks. The new ring went on okay, however now I'm having trouble getting the sleeve back over the piston.

Is there a trick to this?

I don't understand why you had to pry the con rod to get it off the pin, it should slide off the crank pin easily after you remove the cylinder liner from the case.

What is the condition of the liner? Did you check to see if it is still round? Is there an anti-rotation pin inside the piston ring groove that the ring is hung up on?

One more thing, are you installing the piston/ring from the bottom of the liner?

It did not slide easily. What is the proper procedure?

Remove the head and rear cover, remove the cylinder sleeve, slide the piston/rod assembly back off the crank pin, do not cock the rod on the pin. Remove the piston/rod from case, remove ring from piston. Clean ring groove and note anti rotation pin location. Clean/hone the sleeve and insert ring into it just above ports. Install the piston in sleeve from below to push ring square to sleeve and check to see if sleeve is still round by viewing and looking for light between ring and cylinder wall.

If all is good, remove ring and install on piston being carefull not to damage it. Start one end in the groove and work it around. Install the rod onto the crank pin. With the piston at TDC compress the ring and install the piston/ring/rod assembly into the cylinder from the bottom of the sleeve, should go right in if the gap of the ring is lined up with the anti rotation pin. Slide the cylinder down into the engine. Oil well and button it up. Break it in 500 rpm rich with a castor/synth blend fuel and always set the needle 300 rpm rich with a half tank of fuel.

Do not over prop the engine, I would try a APC 17X6 to start.

If anyone else can add to this please do.