Kwik, great video, and lovely planes!
Just a quick question for the guys that have broken cylinders over the last few months. Are you all running standard carbs, or has anyone done the Walbro conversion?
I have my doubts over the capability of the standard carb that comes with the engine, and have recently done the Walbro conversion, but have yet to run it. I am hoping to get it started this weekend, but maybe no flying as the Wx looks a little dodgy with regards to wind.
Anyway, I am nervous about the choke useage as if this engine gets into a hydrolock, I am pretty sure it would contribute to breaking the cylinder, especially using a starter.
Since I have had the engine, I managed to get it tuned in, and all the flights I have had (probably 10 now) the tune has gone out on nearly every flight. This is what prompted me to do the Walbro conversion. Access to the LS needle is difficult, especially with baffled cylinders so I wanted to get the reliable tuneability of the Walbro. That said, I want to make sure not to flood using the choke.
A flying buddy at our field had the FG-21 (I think) which had a similar carb, and his used to flood very easily, and was a pain to tune. I mean, between each flight was another tuning session before he went flying again. In flight, it would lean up, or richen for no apparent reason. Eventually he just put on a nitro carby, a glow plug...and now it runs beautifully.... go figure.
I wonder if the carb is not causing over-fuelling at some point, causing the hydro lock? I think there are only 3 possible reasons for cylinders to crack at that ear 1) poor metallurgy or not enough material on the mount ears, 2) hydro lock, although in-flight this is not something that should happen or 3) timing - pre-ignition causing too much stress
I have not checked the timing, but once I have it running with the Walbro, I am going to retard it a few degrees and see how it runs. Just to negate that possibility.
When I did the Walbro conversion, I did the valve timing/clearances as well. Cyl 1 valve-train was VERY dry....