Hello,

I have two RCV 120 SP's. One purchased at the Toledo show a few years ago (When Wildcat Fuels was the US distributor) and another Purchased from the KMP booth a year or two ago for one of their Spitfires. The older SP was to go into a Top Flight P40 which I was building. The engine sat in its box for a few years unused until this past year when my old trusty EZ zero (800 hours flying time with the same Saito 56) was lost in a mid air over our flying field. A friend had a World Models Zero that he gave me and since then (months) I have been working on this aircraft detailing just a plane old arf into something a bit more elaborate and decided to use the older SP in it. The engine ran fine on the bench and during break in but always had and continues to have a lot of vibration. More so than the newer SP which I have also broken in and is installed in my Spitfire and is nearing completion but not for this season. The older SP vibrates something terrible despite different props (currently I have a Solo Props 3 blade 16" installed). So much so that I seem to have developed slop in the high speed needle. The low speed just free spins without any travel along the threads and allows air to cause the engine to serge up and down. It is impossible to tune. I am confident that this is the problem because after thinking it was just that carb I unbolted the newer carb from the SP mounted in the Spitfire and installed it onto the older SP in the zero. All was fine.....for a few test runs on the bench anyway but soon it too developed the same issue. Supporting my theory is that I can see the black finish on the high speed needles worn off. I thought perhaps the engine was mis timed slightly so I reset that to no avail of the problem. Now I have two unusable carbs, Two unflown and disabled SP's and a warbird formation group (that I have flown with for 15 years) that isn't impressed with all the fuss in getting this engine going and the flying season is almost over here in Michigan. Can you help me resolve this issue Please?