I've now torn down a dozen or so Poulan/Weedeater featherlite engines for conversion (please, save your comments on their low performance! -- you can check my posts from several years ago discussing their porting limitations, and they do actually work quite well on slow floaters like Telemasters and such). (Besides, these things just keep appearing at my house and showing up in my truck bed now that my friends know what I do with wayward weedies! ) All of mine are 19cc or 25cc engines. As a mechanical engineer, I am surprised at the many subtle differences in the design of the crankcase castings (and I'm only talking of the 4-screw backplate models here, not the latest 2-screw backs). I don't know if this was just evolutionary design as the bean-counters forced the engineers to squeeze more $ out, or if there were real design issues. All crankcases seem to interchange with all of the trimmer plastic parts from the other trimmers. All cases also seem to align well with the two-transfer port jugs as well as the 4-port ones. Given that it's not cheap to machine pressure-casting casting molds, I'm curious why so many variations to accomplish the same basic function. Have any of you who have messed with the featherlites noticed this? I first noticed it as I was grinding a case down, and realized it was going much slower than the engine I had done a few months earlier. The main difference was in how the fan shroud was attached to the outside tubular bosses where the back cover screws go in, although there were other changes made on the coil mount and upper crankcase also.

Have any of you put a 25cc jug on a 19cc case and run it? The bolt pattern is the same, although the flow into the transfer ports may be blocked somewhat on the smaller case if it's not opened up some. I'm going to give it a try, although there may be vibration issues due to counter-weight differences -- haven't checked the counterweights yet. The reason I'm doing this is I was given a 25cc weedeater blower that was almost new, but it has a very long shaft on it (like 6", vs around 4" on my Featherlite blower) that is not very suitable for mounting a prop driver since the shaft has a flat down most of its length. So, I'm going to rob the 25cc jug and piston and use the 19cc case. This particular engine I am going to try on the gas/glow blend with glow plug. If you haven't read the "gas fuel with glo plug no ignition" thread you should. These guys are to be commended for having done some fantastic experimentation.