Hi,
I had similar problem. The easiest power improvement is to go to two stroke .50 - 0.52 engine from OS(ringed), Webra, MVVS, SuperTiger(rigned) etc. Then you do not need any(!) modifications - it fits just 1:1 in the place where .46 was, and
you usually gain power almost as ABC type of the .61 engines. Alternatively there isn't much you would gain from
the 4 stroke, maybe sounds a bit funny like old barnstormer ... and some bit of fuel efficiency and maybe a lot
more ... difficult to maintain engine, expensive too. It looks to me the facination of the 4-stroke has gone or it
is going to away at least for the small engines below 1.0; well, let see what the others will say. Of course you
get lower RPM more stable and higher torque at low RPM. But all that would require you to buy new type of
glow plugs and new propellers, while moving from 0.47 to 0.50 you do not have to change almost any thing,
you will just gain like 10-30% higher rpm and about 15-20% power increase too; i.e. 4-stroke is a bit of "waste
of money show" (Well, some one might be right to say that the whole RC is that type "business"). At least there
is one thing for sure: in all RC packages you get the reccomendation to use bigger 4-stroke engine in sense of
displacement, that needs bigger size sleeve and piston and also valves-related mechanics and that is why
Saito had to do special alloys to keep the weight comparable to 2-stroke, and then prices are not that low.
Cheers,
Nick