I have just mounted a new Zenoah 26EI on my 1/5 scale Birddog and noticed that the low and hi mix. screws are facing down. As I like to tune an engine while it is running, i have turned the carb. 180 degrees so the screws face toward the top. I know on the SPE that is not possible. But looking at the inner face of the Walbro carb there appears to be no difference whether the carb adj. screws face up or down. am I missing something? It would seem to me that they would ship the engine with the screws positioned for an easy adjustment whether the engine was running or not.

You missed the pump port. If you look at the carb in its normal position, you will see that the little hole in the intake matched the hole in the carb. If you turn the carb over then the wrong hole lines up.

Apart from TKG's very important comments, the carb is positioned with the needles facing down so that the throttle linkage is a straight run from inside the fuse to the carb throttle lever.

Though I don't advise anyone to do so due to the possible danger to one's knuckles from that spinning prop, I adjust my engines running with the carb needles facing front, but I use a little tool I fabricated that fits over the head of the needles which makes adjusting them a breeze and also quite safe too.

Karol

karolh,


Got a pic of this little tool. Might have to make myself one.

Sorry no pic available Zippi, but the 'key' as I call it is a 1.5" length of close fitting metal tube that fits over the head of each needle and has a small flush fitting cross pin .25" from one end that fits into the needle head slot. The other end has another pin which extends about .25" either side which is used to turn the key. As the needles differ in size each needle has it's own key. A really snug fit is required to keep them in place on the needle with the engine running.

Karol

These tools work great.....I've done something similar, with an appropriately sized brass tube, fitted onto the end of a screw driver. The brass tube slips over the needle, and the screwdriver, or PIN in Karol's example, locks the tool into place and will not vibrate off while adjusting and running the engine. I made a set of three, different lengths, for different reaches through cowls of various airplanes. If you select tubing one size larger than what barely fits over your needles, you can come at the needles from an angle, which is really handy for staying away from the prop! They certainly make adjustment much safer, if you must do so while the engine is running.

Visit the B&B Specialities site and you will see they offer a small knurled carb needle tuning tool which I hear works quite well too.

Karol