Jan 6th, 2006
Even though I crashed on landing, this was the best flight so far!
Everything was going well. I took off on the first attempt and was winging around the field like I knew what I was doing. My turns were still relatively flat but I felt better about everything. There was more authority in my input and I was getting used to the routine. When I let out the trimmers I could feel a difference in the way the wing behaved. It is much crisper when you initiate a turn and it’s hard to tell at altitude but I felt faster. The whole thing was just much more comfortable than the previous flights.
Brian had me do several figure eights and then asked me to go north, turn and descend to the LZ for a low pass. I was feeling real good about the whole thing. My decent was perfect, I wasn’t going to overshoot or fall short. But…when it was time to add power and climb-out the motor started to bog down. The motor was spinning at maybe 4000RPM and I was just barely descending. I had noticed a delay to power in the past and kept hoping the Snap would start to wrap up. It didn’t and as I flew by Brian and Doug at about 10 feet I was still hoping for a burst of power, at 3 feet I lifted my legs and slid into the earth very softly. The prop was “cutting the grass” during the last couple of seconds but when I hit, something flexed and the prop struck and broke a two inch chip off the end of the blade. It‘s repairable but not for awhile. Even though it ended badly, it was a great flight.
At first I thought that the brake handle had somehow got between the lever and grip which would have prevented it from closing all the way, but the problem was with the Walbro Carburetor. If I had increased throttle gradually, I think it might have powered up just fine, but when I went from idle to full throttle very quickly, it lugged down. Eventually I learned how to tune the carb so that it would come up to power even when I mashed the throttle hard. It never did get smooth and there was still a delay, but after a short lag, I would be at full power. Another issue with the Snap 100 is that it had a very narrow power band. It would advance smoothly from idle to about 4000rpm then it would leap up to 7500 and advance smoothly again to 9200. The result was that I was either climbing like a banshee or descending. There just didn’t seem to be a cruising speed for that motor that fit my weight and wing.
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A couple of days later I took the paramotor to a small engine repair in Golden that Brian had recommended. I wanted to have them check it out and adjust the carburetor. A couple of days and $125 later I picked it up, only to be told to increase throttle slowly to prevent it from lugging down. I think the guy didn’t really want paramotor business and was probably intimidated by the spinning prop. I wouldn’t be surprised if he never even fired it up. I sure couldn’t tell any difference in the way the engine ran. Obviously I wasn’t going to get any help from the lawn mower repair community so I began to research two stroke motors and their carburetion. I was able to get line drawings and owners manuals online but the best tips on tuning the Walbro card came from the PPG forums.