Hi res photos are courtesy of Rob van der Heijden, he took them while working on his ST20/25

Field experience.

  At the time of this writing, the system has been in use for over a year now on a German Moki 1.80 (World engines) and a ST G20/23. In that period it has worked flawlessly, until all of sudden the idle mixture shifted, and then soon the engine went lean on full throttle. Upon checking the internal fuel filter, the very fine filter mesh was completely clogged with  fibres which formed a dense mat. This in spite of the fact, that an external filter was used all the time and cleaned at regular intervals. After cleaning, all fuel needle settings could be returned to their respective original positions. Because cleaning the filter required the Walbro to be disassembled, a thourough check was made on all parts to verify the horror stories on internal corrosion coming from the German MVVS distributor (the MVVS 1.20 is fittet with a Walbro carb). Corrosion traces were found on the inside of the pump diaphragm cover, but not on the internal parts which were constantly submerged in fuel. I coated the cover inside and membrane outside with after-run oil and will soon know if that helps.

Some times, the pump needs to be primed first, and needs some running time, before proper fuction sets in. A different fuel pump might be better still. The Walbro valve membranes are sensitive. I am eye-balling a perry back cover mounted pump as a substitute, but plan to keep the metering diaphragm part

Closing the exhaust while flipping the prop, will prime the engine. As Dennis van Tooren suggested to me, I use a T-connection in the crankcase pressure line to the Walbro and inject 2cc (1/16th fl.oz) of fuel into the engine, so I know exactly the amount of prime used. Flip over the engine three times, add glow and finally bump the prop against compression. That is all that is needed to start. In Winter cold I had to prime for every start. During Summer, no priming is needed after that first start of the day. After the Mods made as in STwoes, the engine runs absolutely reliable at all throttle settings. The regulated fuel pressure allowed me to exactly tune the Supertigre's carb in all throttle settings, but that is a different story alltogether.

The Supertigre is an absolute pussycat, light and with power to spare. It runs reliable from 6000 rpm up without any signs of overheating. I run it in the 7000 to 8000 RPM range with wooden 17x10, 18x6, 18x8, 18x10 and 20x6 props. If you need more power, and don't object to the noisier operation, just fit a smaller prop