I don't know if I've mentioned this before on this forum, but a few years back I bought an Irvine 40 MkIII from a LHS that was going out of business, for about 1/3 the cost of a new one. It was, as best as I can determine, one of the last made in England. I decided to convert it to CL and got a venturi and NVA from Just Engines. I added one head shim and mounted the engine on a Tutor II. I'm using a Hayes 6oz. (way too big) tank and running Powermaster GMA 10/22, with a 11/4.5 prop. I haven't flown it, yet, but the engine was broken in during some "dark-side" flights, and it ran quite well. I ran it, today, with the airplane tied down on a table. It started easily and I ran it at a pretty hot 2 cycle where it was showing very faint exhaust smoke. I didn't have my tach, but I would guess it was above 10 K by the way it hummed. I unhooked the plane and held it upside down, sideways, etc. and it didn't seem to change RPM at all. When I held it pointed nose up, it wanted to lift out of my hands, still not changing RPMs.
I took a long time to get to my question, but I'm wondering if I was running it too lean. It ran over 6 min. on about 2 oz. of fuel. It seemed to be very happy at that setting, and didn't seem to get too hot, and it never came close to sagging. I'm anxious to get it in the air, and see if it's as good of an engine that I think it is.
Glen Wearden