Guys,
Seems like there is a variety of experience with the Enya .15-III as a smooth--or not--runner. The engine was pretty clean when I got it, but since the last attempt resulted in more shaky breaky, I took it off and cleaned it well for storage. As in, a day in the hot antifreeze. That might have removed any notional buildup of carbon on the underside of the piston, but the liner does not slide out, so a visual inspection and cleaning was not feasible since there is significant taper in the bore, such that the piston does not simply slide out the top. Much more taper than you'd see on most OS engines. Still, the cleaning might have made some difference and it is worth testing. The engine appears to be broken in and has an excellent piston fit.
It is not the prop. I could not agree more about the futility of APC bothering to drill holes in their otherwise very fine propellers. Either they have no tooling, worn out tooling, or put their least skilled people on the drilling operation. So I understand Dan's comment. (There is a thread somewhere here that discusses this issue in detail, and you can see the different opinions on the subject there. Unfortunately, I don't think it addresses the time span for rework that Dan suggests, such as when the cows come home. In my personal experience, that time period is not long enough to repair some APC props unless you align a cutter to the molded ID and bore it all the way thru and then make a close fit bushing that presses into the prop and just slides onto the engine crank.) In the particular case at hand, I can tell you that this is a wooden prop reworked from a Zinger "kit" and balances and tracks perfectly. Of course, I am willing to check again to add emphasis to my earlier certainty....
I didn't think there was any difference between the OS .15FP and LA mounting dimensions. There isn't in any of the larger engines, but I don't have a .15FP to check in this size. And when I did check the .15 LA that I have, it is not like the Enya .15-III, so I don't understand how anyone successfully "bolted it in," unless the FP is like the Enya and unlike the LA???
So maybe the Enya .15-III likes a pretty stiff nose, else you get what Dave Moe and I have seen. It wasn't really on my list to do a nose job on this little guy, but the more it hung around the house, the better I liked the color scheme on the wing. Kind of attached to it now.... Just sick of doing nose jobs on Other Peoples Planes (OPPs).
Still, as an engine this one seems like it is more than decent, but maybe short of being a jewel. Hard to give up on that....
The Divot