My favorite FOX 35 has a problem that I can't figure out.
This engine for the last four or five months has been on a Flitestreak and running great, flying stunt an occasional informal combat match and even a little racing just for fun. During all this I have used Sig 5/25 with a little extra Castor added in, a 4oz uniflow tank, 10/6 APC prop and various plugs that all seem to work fine.
This is an older FOX that has the squared off exhaust, no muffler lugs or any material at the center of the exhaust port. On the bypass side FOX and "35" are raised letters and numbers. the original needle valve was the flat spot or blade type along with the valve body having two holes.
On the last couple of flights before things went bad I noticed a lot of black goo that seemed to come from the lower part of the back plate.
I operated the engine like this for at least a dozen flights with no problem until it started running ruff and lost power. My feeling at the time was that the back plate gasket had failed and caused the problem. This was replaced along with a new head gasket and put back in the airplane. No luck, the engine now will only run for a short time sputter then die.
I have done all that I can think of
1) Five different glow plugs, 2) Three different fuel tanks, 3) New needle valve assembly and fuel line, 4) Fresh FOX 10/20 fuel with extra Castor added. All of this has not helped at all, compression is good, tanks O.K. and the glow plugs are hot but the engine will not stay running for longer that 20 seconds or so. Any ideas other that an 0.S.25 ?