The O.S engine gave me a little headache. I ran it at home a little bit, and it ran strong and started like any O.S motor should, i.e. with a light flip of the prop. It tached 10.000 rpm on the APC 11×12 and idled smoothly. All was well and then I tried holding the nose up, and it leaned out badly. A lot of tweaking later, I was unable to fix it. I re-did the fuel plumbing and moved the tank a lot further forward and hoped that would solve it. It may have been optimistic having the tank as far back as I did without using a pump or header tank.
On the field yesterday I had exactly the same problems. I switched from an O.S 8 plug to an OS F, and that did nothing. I tried a smaller prop, an 11×9, and that helped a bit. I then tuned it some more and eventually it ran strong. I had one flight where I landed early because I could hear it leaning out a bit in loops, tuned more, and then suddenly it ran like nothing else mattered, not missing a beat going up, down, sideways or anything. Success! The third flight was suddenly bad again, leaning out. Landed in a hurry, tuned, and suddenly it ran great again.
I have a successful track record of making stubborn engines run good, and I don’t intend to let this one beat me. I suspect the pipe is slightly too long, and I think shortening it might do the trick. I will also try an 11×10 to load it up just a bit more.
The plane flew just like you’d expect. I had some wild deja vu’s while flying. I have lots of flights on the old version of it, so it behaved as I remembered, which is a strange sensation when I was mentally prepared for a maiden flight! I was also surprised at how well behaved it was on takeoff and landing, and how well it tracked straight and level. It has no vices whatsoever.
Here’s a before/after photo, with at least 13 years between the two: