SpaceCase

My Feedback: (4)

OK your talking with a guy who has a saito 72 and loves it. I know a 72 saito and this is no 72 saito. My 52 o.s. heli four stroke I got is kinda a dog I guess. I got a tuned pipe on it but am woundering afew things. Can I put a carb on it from another manufacturer? Also can I bore out or replace the piston liner/piston with something bigger? I dont thing going to another engine would work, a ys 53 weighs a pound. The os weighs 14. oz, the os 32 2 stroke weighs 10. oz. Im trying to go agains what ever one has told me because that is the american way. Inovate! People always say you cant use a four stroke in a heli. Well how come people always say four strokes swing bigger props better?, arnt the 550 blades on my heli just big "props"?

w8ye

My Feedback: (16)

I've read some talk on here about blending the valve pockets into the intake manifold and exhaust manifold. You can also run a straight pipe on them if you already have good fuel draw.

There's not a tremendous improvment.

Might spec out a Magnum 61? Another fellow and I at the field don't have all the power problems that the guys with the OS 52's have.

Maybe we are lucky?

Jim

Chinooker

If you want more power there is not replacement for displacement. Magnum .61 isn't much more powerful than a OS .52. The Magnum 4 strokes are typically weaker than their peers.

A Saito .72 would be a noticeable difference in power over your OS .52.

4 strokes don't do well in heli's because (contrary to urban legend beliefs) they run hotter. I know it doesn't seem to make sense that an engine that fires less often than a 2 stroke runs hotter but it is true. I believe this is because a 2 stroke draws raw fuel in through the low end of the engine and absorbs a lot of heat. 4 strokes don't do this.

Ask any heli guy who has run a 4 stroke and he'll tell you it overheats in the summer and a 2 stroke runs cooler.

William Robison

My Feedback: (3)

Spacey:

Doesn't matter what carb you put on it, you aren't going to get any more power by doing it alone. The cam timing, the porting, and the exhaust are all restrictions you have to overcome.

The cheapest way to get an immediate powr increase is top change the head ratio on your bird, let the engine wind more. And to do that you will need stronger valve springs.

You can also re-profile the cams, grind the lobes for longer duration and freer breathing. This will have an effect on the idle, so be careful if youo get into this.

If you aren't into regrinding cams you can pull the valves down to zero clearance - so long as you can feel the least wiggle in the rocker you have enough clearance - this will give longer duration too, without a great effect on the idle, but not a great increase in power either.

Anything you do to increase the power is going to increase the loading on all the parts, with a corresponding faster wear out of the engine.

You might check into the OS 40 4c engine for r/c cars, OS rates that one over 20K rpm, if you use the cam and valve springs from that one you might get a great rise in power, and if you set yours up the way the car 40 is yours might last a while too.

Just some things you can think about.

Best way was in your post, the first post on the thread. Get a Saito FA-72.]

Bill.

SpaceCase

My Feedback: (4)

sweet I already have a saito 72. It weighs a pound and the os 32. weighs 10 oz. Its six oz. over weight, not too bad. I love that engine too. Im going to design another cooling shroud, its going to collect air off the blades and paddles. Itss too bad I cant use that o.s. 52. I guess they make good engines its just when you get to four strokes there is no room for JV or amatures. Some four strokes really stand out. That saito will pull my us 40 straight up, takes five feet or so of runway, if you call it that, heh heh heh.