2 or 4 Stroke??
 

My 4 st's are much cleaner than 2 st's There are times when I don't even clean my planes after flying. I guess it depends on where you point the exhaust.

2 or 4 Stroke??
 

I think you hit the nail on the head rctrax. Blackie, you must have just the right combination of where your exhaust is pointed along with the aerodynamics of your planes.

I use mostly OS 70 Surpass, OS 91 Surpass, and YS 91AC.

For 2 strokes, I use mostly 40-50 sizes.

Like rctrax says, most of the time I don't even clean my 4 stroke planes, whereas my 2 strokes (and I'm not running them rich) will have a stream of thick oil, 2 or 3" wide, running the entire length of the plane.

With my YS91AC, blowing smoke between the bipe's wings, it still doesn't leave nearly as much oil as the 2 strokes do.

2 or 4 Stroke??
 

And thanks for the info rc_sport

2 or 4 Stroke??
 

Actually its exhausted inside the cawl I had to cut a large hole out the bottom and I just amied it down. That may be the reason why its ail over the bottom of my plane. I also neglected to mention that I am running a high oil content of fuel. YS 20/20 Power Master.

Randy

2 or 4 Stroke??
 

Maybe that's it. I run Cool Power 15% in everything, 2 or 4 stroke.

2 or 4 Stroke??
 

If I am not mistaking the OS will be more forgiven as far as fuel consumption goes. I tried 15% in the Saito and it did not like it one bit. With the 20/20 on the Saito I get a smoother running and more powerful engine.

Randy

2 or 4 Stroke??
 

I just bought a Magnum .52 four stroke, and I have to say as far as fuel goes it uses far less than any of my 2 strokes. I'm still breaking it in now, running it sloppy rich and it still will run 23 minutes on an 8oz tank. I'm thinking of switching to a 4 oz tank. I should get around 10 minutes of flying time easily with a 4oz tank.

The only negative thing I can see about the Four stroke is it seem to vibrate a lot more than a two stroke. Just make to check your screws for tightness often.

TiggerFlyer

2 or 4 Stroke??
 

I think all the bases where covered to some degree in most of the posts. 4s's are heavier, larger, cost more, different to adjust and require more maintenance. Most produce power at lower rpm and can swing a larger diameter prop. IMO the OS 91 fx should run no larger prop than a 14x8 but the OS 91 surpass can swing a 16x6. 2 strokes do not usually like a big load and can get real hot. My 4 strokes sip fuel better than my 2 strokes. Note that the ST 3000 is designed to spin a large prop at lower rpm the ST 2300 a small prop at higher rpm and your pay for power in the YS by cramming more fuel into the chamber with cuts fuel economy. I prop my 4 strokes to run at about 9k on the ground but most of my 2 strokes at better than 10.5k. By all means try one but maybe your third or fourth engine. Make sure you run a 4 stroke a little rich - you don't want the prop come off from a lean detonation. 4 strokes do sound great. Each type of engine will have different characteristics.

2 or 4 Stroke??
 

Blackie, I switched to 30% to run in my Saitos, the difference is awesome.