I have a related question Dave - I took my regulator off yesterday (110) and ran into a similar problem - how do you tell the correct orientation to re-install it? There seemed to be a little blob of metal on the regulator in one spot, but I couldn't find any matching registration marks on the engine to line it up. The motor seemed to run ok when I re-installed it, so I guess I got lucky.

More questions: The diaphram in my 110 has a small fold or crease in the middle. When you first take the reg off, you can see a bubble of air between the diaphram and plunger under the crease. Is the crease supposed to be there, or should the diaphram be completely flat?

I am having some problems with the way the motor runs, and I am taking the advice you gave a number of other folks and ordering the replacement plunger for the 91 (I'll get a few diaphrams and springs too). While I'm putting in an order at Central, I could use some fuel too. Would Magnum's YS 140 DZ blend be a good choice for the 110FZ? From Magnum's website, it appears to be a 30% nitro blend, but I don't know the other additives (assuming low viscosity lubes like heli fuel?). I've been running Coopers 30% Plus grade, but Brian is not yet back to producing fuel since he moved to NY.

Thanks,
Kurt