2-ring vs 3-ring piston

[2botes]

I have a piston issue...I'm rebuilding a 70ETLH Yamaha ('87 3 cyl 2-stroke); that was built factory w/ 3-ring pistons, so I ordered 2x replacements (STD size) but rec'd 2-ring in lieu of the 3-ring piston I thought I ordered per the PN I was given from a supplier. I am being told these will work for us & shouldn't be a concern; also told that there MAY be a certain block design that requires a 3-ring piston over a 2-ring.

Does Yamaha have varying block designs for this model? Will these 2-ring pistons work well as a replacement?

Any help is greatly appreciated. Tks.

 

[2botes]

OK, well, I've had 0 responses here. But an FYI, I have learned since that as longe as the piston is dimensional the same (i.e. OD, Length, pin-to-top of piston dims), 2-ring piston will work.

Now, moving on, installing the assembly in the block. I haven't the proper ring compressors in my tool arsenal. Has anyone installed these by another means?

 

[flyingscott]

Use your fingers to fit the pistons ring. Put light pressure on the piston and work the ring in don't push hard and make sure the locating pin lines up with the ring gap. If you push hard when it goes in you could break the second ring so just light pressure.

 

[99yam40]

I mhave used plastic ty raps to cinch up the individual rings to the pistons and as you work them into the cylinders just cut and remove after the rings slide in.

I have read that rings transfer heat from the piston to the cylinder walls, with only 2 instead of 3 it will not transfer as much heat seems like

 

[2botes]

Tks flyingscott....all went well. Finally got this thing together & cranked it up, which it did on first try. Tks again.