Originally Posted by
Cat 1
Got out flying tonite and got to try the Skinny bore carb on the ST.45. Magic!!! - Power might be down a bit, but I propped down to a 10X6, got the revs up and I think it as powerful as all but of a few of the .40 size glow engines I use to run. Not typical .45 power but a good solid sport .40 performance. Throttle transition is great and great response from long extended (cool right down) idles. Got some video but haven't processed it yet - It was super windy and I have to take out some content so you all don't think less of me
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All in all the bore reduction project was a successful experiment in my books - Took away the need to leave very rich to insure good in flight mixture - I'm still on the rich side and sneaking down slowly as I'm a bit gun-shy from the big bore setup.. mixture is very "non-critical" now - still a little touchy around idle but very much improved.
I did notice one thing while playing with idle mix - You must be on the rich side of the "curve" almost to the point where you think it might be loading up a bit. When the engine is hot (just throttled back) it might seem a bit rich and leaning helps it run "better" but as the engine temp drops it need the extra fuel to maintain idle. Its understandable - but not an effect usually noted on a glow engine.
I so far never have tried the bore reduction thing, but I can imagine its advantages. Motorcycle manufacturers play with carb bore sizes all the time to adapt a given engine to its intended use (same engine in a sportsbike or a cruiser, they ARE going to have different sized carbs/injectorbodies).
Bit amazed about the "idle mixture thing" though. So far, my experience has always been "as lean as i can get it", which for the singles is not so much an issue, but the twin and radial, due to their residual uneven mixture distribution can be a bit tricky to find, because one cylinder remains a bit rich and tending to load up while another tends to lean out and stop firing. So far all has been doable and even reliable (both Radial and twin have never quit in the air OR on the ground) but never as easy as a single. Also never been really problematic.