John,

I've been following your build with interest. Always nice to see scratch or scaled up/down projects.

One comment regarding your 91 FX: they are widely rumored to cause the fuel to develop bubbles due to vibration at the needle valve assembly on the backplate. There was a revision of the engine by OS and the later ones were made with a standard backplate with a bolt on assembly for the needle valve. From factory it came assembled on to the backplate but was easily removed and attached to some other location on the airframe. This solved overheating and dead stick situations which were being widely reported. If you take a look at the current engine on Tower you'll see how the engine looks now.

Your engine appears to be of early vintage with the backplate and needle valve as part of the same assembly. It might be worth checking into a replacement backplate and needle valve so that you can locate the latter somewhere else on the model. I believe that a simple ply plate on the side of the cowl would be a fine location. It's just a matter of getting it off the engine case.

You might find this thread of interest:

http://www.rcgroups.com/forums/showthread.php?t=147756

I have one too but I bought it from a friend and have yet to pick it up (a year later...). When I do later this summer, I'll probably do the same on mine if its of the older vintage.

Keep up the great work and thanks for your thread.

David.