Chainsaw Repair

The early 266 was an open port and had a full circle non windowed piston like the 61. Then with the closed port cylinder came out on the late 266SE and the 266XP that used the full skirt windowed piston like shown before (similar to the 181 and 2100 thin ring). In the 268XP (same bore as 266) and 272XP (+2mm) they went to the slab sided semi windowed piston we are all used to in modern saws. 

If I were picking up a new piston for a 266 I'd probably use a piston for a 268, I think Meteor makes a nice one.

Meteor makes a nice windowed piston for the closed port 266SE/268XP saws.  They also make a non-windowed piston for the open port saws (such as late 268).  Their terminology is somewhat misleading however.  I've seen where they call the non-windowed piston (which should be used in the open port cylinders) a "closed port" piston.  Also seen where they've called the windowed piston (that should be used in a closed port 266SE/XP or 268XP) an "open port" or "open" piston. 

Various sellers (on ebay and elsewhere) further the confusion with their descriptions of the Meteor pistons.  I have seen the non-windowed piston described as "for closed port cylinders" (which it is NOT the right choice for), and have seen the windowed pistons described as "for open port cylinders" (which it is a poor choice for).  Thankfully, they often will show a picture of the piston that they're selling...............so you can still make an informed decision.  If you have a closed port 266/268 jug then buy the slug that looks like a 272XP piston....