Right. There has been some debate and indeed heated arguement regarding the differences between 2 and 4 stroke engines in Freestyle/AA Models.

I notice the YS seems dominant.. WHY? Can anybody honestly put forward a reason why 2 strokes are not widely used?

Has more torque at low end, can swing larger aerobatic props, on YS's, quicker throttle respone.

Ok... then how come the YS110 and the OS91FX swing the same prop... the YS would come out at 80g heavier on the airframe... and does the YS (4ST) really have a quicker response how do you quantify that?

I am not sure about ys. I have flown nothing but 2 stroke's. I just got my first 4 stroke. A Satio 72. I gotta tell ya. THIS THING ROCKS !!!!!! My 540 went from real good to AWSOME ! It is soooo over powered it's silly. Gotta love it.

Ya it's 4 oz's heaver than the 46, and yes it's $110 more but you know what? I DON'T CARE !!!!!!!!

They say that once you try a 4 stroke you will never go back. I think this is very true. Now i am looking at the little satio 40 for my .25 profile.

If your thinking about trying one don't wait !! Just do it. You will not regret it.

Yes,I like the superior power and thrust of 4strokes,but mostly I just can't stand the sound of a 2stroke .

My 2 cents. Just got my first 4s 2 months ago (ys 63). Wow!!!ran right out of the box...have not had a problem with it yet.

Most of the guys at my field only do 2s and gas engines, only a handful of 4s, and only 1 other ys (he has several problems with it...I told him I would take it off his hands for free).

While I believe you pick a motor based on the application I will always consider buying 4s over 2s (except for speed planes).

Oh, did I mention, since I have the only good running ys at the field, I am the envy of many (they just cannot get over how quiet and powerful it is...).

I did! 2 strokes rule!

4s are not for evey one. But for the type of flying i do....there perfect. If i was to do a speed ship it would defintly be a 2. But i fly for fun. hovers, down low and slow. Tumbles and flip's. 1/2 throttle knife edge loops. Pull outs so fast you scare your self.

LOVE THEM TO DEATH !!!

Mine was on a Top Cap. Gave me nothing but headaches. shook the poor plane to peices, dead sticked a lot. Couldn't get it to idle less than 3000 RPM (must be that "low end torque" everybody talks about )

Recently switched it out for an Irvine 53. Ahhh so much better.. never dead sticks, low vibration, it idles, pulls out of a hover every bit as good as the saito 72 did, all for half the price.

there is no question that the saito 72 weighs the same and kicks a 46 2S around, but the same can be said for OS 50SX, Irvine 53, Webra 50....

Want to trade? I have a brand new os 50 sx in the box i will trade you for the satio 72.

Convertign my cAP 232 from 2 to 4 stroke changed the model because i could swing a larger prop.

I think that 4 strokes have the torque to swing larger probs, and this is what's wanted in 3D... loads of braking, yet loads of thrust once it's spinning... lets face it, we're not gonna be racing a 3d model.

I pride my self on how SLOW i can fly. (grin)

I use them because they are more efficient. Four strokes generally use have the amount of fuel and have 75% of the top end power. Four strokes are becoming more powerful.

Ys is really powerful. The ys 63 is suppose to be more powerful than the saito 72 and the ys 91 is suppose to have more power then the os 120.

I just got a os 91 with the cap 232 that I got. I like that engine. I think I needed a bigger engine to balance the plane anyway, so I can not complain about extra weight in the nose.

Right, well thanks for this... but if we strip back a) the economy, b) the noise c) the cost d) prop size e) all 'on' and 'off' pipe problems e) all cosmetic attributes.. and get down to an installation into an AA or freestyle model you think 4stroke is best? More power? I don't think so. Less weight? Nope. More torque? REALLY? When you put the SAME plane with the SAME set up with TWO power plants.. say the YS110 and the OS91.. who will hazard a guess as to the best performance?