I was interested in your FL 70 problems as I ran into difficulties after less than 8 flights and a run-in period. A colleague pointed out whilst spinning the prop that there was a tendency for the prop to slop either side whilst at compression. This he suggested was possibly premature wear on the connector arm and the crank pin. The bushing is brass so itis the softer metal. The engine went back in the box and was send off for warranty repairs. I was informed that the cause was looseness between the piston and the cylinderliner. Thepiston was able to pass the top of the liner and lock at compression causing a 'bounce' effect. This I was told was not a warranty item and would cost 75 dollars to repair after discount because the warranty was in force. This was staggering as the OS fame has promised years of faithful service not an engine rebuild inside a gallon's use of glow fuel (15% Nitro and 17% oil mix)
The warranty was refused and there's no point in complaining and the fact that the engine had clearly failed on the 'business end' which is where the wear is going to be, did not matter
as it seems they only guarantee the bits that arn't going to wear. Beware! my friends of the OS warranty - the rules are non negotiable. Maybe the reason why they have discontinued that ringless engine is that they have had complaints of premature wear.