OS 61 fs

Does any one know how much power the OS61 fs should have produced when new. This engine is about 20 years old but has done very little running, starts first time and has loads of compression. It does not have quite enough power for my plane and i was looking at the ASP 70fs from just engines as a replacement. that produces 1.1 kw /rpm. And the ASP 61 fs .83 kw/rpm.

Edited By CARPERFECT on 16/06/2012 13:42:42

In a word Carperfect...no idea... but I would say that your OS61 comes from the fairly early days of 4 strokes so is likely to be less powerful than a more modern engine....even if the more modern engine is an OS clone....

I have both the ASP61 & 70 4 strokes & they are both excellent motors....The ASP 61 is effectively a "big bore" 52 & shares the same crankcase as the 52 making it very compact....the 70 is a good bit bigger all round.

What model do you have....? It might be easier to advise you knowing the model & type of flying you want to do....

The plane is a Dave smith Areostar 62" pattern ship from the mid 90`s. I have had the plane from new and it was fitted with a OS 61 FSR. Having changed flying clubs and being only able to fly 4 strokes the 61 fs was the biggest one i had in the hanger. I have just found the original documents that came with the engine, and it says it will produce .9 bph. If my calculations are correct then .9bhp converted to kw is 0.67113000. this is well down on power when you compare it to modern engines. The 61 FSR produced 1.7 bhp thats 1.26769000 kw. So the ASP 70 fs looks about right at 1.47512404kw. A bit up on power on the FSR but twice as much as the 61fs.

I have a MkII OS61 (the one that came with no muffler) and its certainly not suitable for that plane. I would be really surprised if the ASP70 matched a FSR. I would go for a ASP80 to avoid dissapointment