This past two weeks I've had my fuselage out (the wings are not bolted on) for some test taxiing. This past Friday I was out on the 6000' runway and running from one end to the other. I had a fellow pilot who has a light sport plane at the airport who was watching, tell me that I was running down the runway well over the speed at what most planes would be airborne. I have found that you certainly don't want to be dancing on the rudder pedals at all or the tail gets twitchy real quickly. Fortunately our runway is 150' wide too. I did four complete passes and have some questions.
I have an 1835cc VW with a Rev-Flow carburetor. The engine fires the top set of plugs on a slick magneto and the bottom set (automotive plugs) fires off of the electronic ignition from Great Planes. The electronic ignition is preset to 28 degrees before top dead center as was recommended in the setup instructions. That's of course why it's not started using the electronic ignition. The engine is started using the mag with it's mechanical advance and once it's running the electronic is switched on using a switch on the instrument panel. When it's switched on, it's like lighting a rocket in the cylinders as the engine really picks up power, I'm sure due to the hotter spark of the electronic ignition. My problem is in getting the engine to idle correctly. With the electronic ignition turned on, the engine backfires some during slow taxi (at this point there shouldn't be any other kind, right?) and I believe it's due to the preset timing of the electronic ignition firing too soon for the slow speed of the engine. If I taxi out using only the mag it seems to idle slowly at a lower RPM but this does seem to load up the automotive plugs so that when the electronic ignition is finally turned on it takes a few seconds to clear the plugs. I've had it stall several times at idle but I think that I just need to preset the throttle slide open a little more, as it might be set so it's too far closed and cuts off the air flow when the throttle is all the way closed. This is with the mixture set at full rich by the way. I need some thoughts on how to get this to fire evenly with the electronic ignition on at idle. Does the timing need to be decreased some? I believe I can conquer the idle problem just by readjusting the slide in the carb a little but I'm puzzled on the backfiring at idle. Once on the runway when I roll in the throttle, it really accelerates quickly and is smooth running. I don't have the airspeed indicator calibrated, but I've seen it indicating 75 MPH, and when I pull the throttle back it seems like it will coast into the next county. I don't even want the wings on it yet because I don't want to find myself airborne and not ready. I can tell the tail gets light on the tail wheel as the noise coming from the tail wheel gets quieter and I can tell it's getting light on it. I haven't tried to pick the tail up yet. I'm planning on tying it to a tie-down ring and with the air from the prop seeing how much stick it will take to pick it up. I figure with about a foot and a half of good strong rope it will let it come up but not go so far as to nose over. Any suggestions on testing are appreciated. Thanks, Neal Hornung lt1corve...@earthlink.net EarthLink Revolves Around You.
