Which 4-stroke to purchase?
 

520g = 18.356 oz.
560g = 19.768 oz.

I think you "referred" to the stats. I "checked" the stats. ;-)

Again, published weight figures are unreliable. Your stats are different from Shemp's stats. And both sets of stats are different from my actual weighings. Your weight checks might bring different results than mine.

But by stats or measurements, the Saito .91 is lighter than the O.S. .70 Surpass II! In some cases, a big deal; in other cases, not a big deal at all. In my case, I wanted to try an O.S. four-cycle engine. Tower had them on sale, AND gave a free Futaba 9001 servo (worth over $40) with each purchase! I've heard the .70 Surpass is a sweet engine, so I snagged one.

I've tried three Saitos, and a Magnum .52. So far, I'm a Saito fan. Next, a Y.S! Maybe that will change my preference....

Happy New Year!

Re: Which 4-stroke to purchase?
 

OS...reliable but pricey...kinda heavy.

YS...powerful but REAL pricey...a little heavier, too.

Saito...powerful and pricey, but light.

The Saito would be my first choice. It does take a while on the bench, if you are inclined to bench run an engine, to get it properly broke-in. After that it is virtually flawless in its operation for many years if properly maintained.

...NOW, go buy what you gotta go buy...the choice is yours!

91 4 stroke comparison
 

I have ran all three engines on the same plane. The OS 91 Surpass ran a little better than the Saito 91 (better throttle response, fewer dead sticks), although the Saito did have a better idle. I used 15% fuel, 14 x 6 prop and an OS F plug. The OS would pull the plane vertical a little better than the Saito, in spite of the OS being heavier. The Saito used quite a bit more fuel than the OS. I adjusted both engines to run about 300 RPMs below peak.

The YS 91 outperformed both the OS and the Saito in all categories. I used a 15 x 7 and 16 x 6 props, 20% fuel and an OS F plug. The YS used fuel at about the same rate as the OS. The YS idled better, had better throttle response, pulled the plane vertical a little better than the the OS and had less deadsticks than either the Saito or OS, especially when flying inverted or with the engines at idle speed. I think the YS is about 4 ounces heavier than the OS.

All 3 are good engines. I favor the YS, especially the pressurized fuel system that keeps the fuel mixture constant throught the flight. You can also mount the fuel tank on the CG, so the CG doesn't change as the tank empties. The YS also does not have a breather tube on the crankcase to contend with. All 3 engines are similarly priced within $40 or so.

CAPS
 

I NORMALLY WRITE IN CAPS BECAUSE I KNOW THAT MANY OF YOU GEEZERS ARE HARD OF HEARING.

best 4 strokes
 

I agree that the ys is a quality motor and it's performance is on a higher plane than the os and saito. With it's performance comes some complexity. The original request was for a first time 4 stroke. It has been my observation at our field that first time 4 strokers can become frustrated with setting up and adjusting the ys. It has also been my observation that first time 4 stroker's tend to lean the motors out too much. This is why I recommend low nitro fuel with partial castor oil content. The Saito's like to run rich, the os's will run at a broader needle setting and develop good power with low nitro fuel.

If weight is the primary concern go with Saito. If performance is the primary issue ys is king. For ease of use I would rank the os first and saito second for first time 4 stokers.

Which 4-stroke to purchase?
 

:rolleyes:
OK. I'm late on this thread but there are a couple of things I roll my eyes about.

Weight!!! Come on guys. I've never built a plane for a .70 to .90 engine that one once in the nose would make a hill of beans difference. Nuff sed!

Power to weight ratio! Means absolutely nothing when comparing engines. The engine doesn't fly alone. (Unless you messed up the engine mounts and they broke loose). Power to weight means something when you compare power of the engine to the weight of the completed flying machine, just like we do in the "grown up airplane world" I work in. Even then, alot of other factors come in to play. Wing loading for one.

Give it a rest and don't confuse this guy by splitting hairs.

And always use a bit of castor oil in the fuel. Especially in those ABC engines.

Tony

Which 4-stroke to purchase?
 

I was wondering in those test that were performed what percent of nitro was used in the engines. You see satios like high nitro and run considerably better with it. Go check out the review of the new Satio 100 verses the OS .91 at Horizon. You will notice that the satio keeps on making power as the nitro is increased beyond 20% were the OS really does not have a change. This leaves me to believe the OS has a high compression ratio than the satio which would seem to be the reason they run better on lower nitro fuel. I would like to see a comparison with the Satio .91 using 30% heli verses the OS .91 Surpass using 30%. I believe the results would come out more in favor of the satio here. An by the way Horizon recommends the use of 30% heli in satios.

Horizon says to use 30% ?
 

Where did you see this recommendation to use 30% heli fuel in all Saitos? I have often thought of doing this with my .72 but was advised against it because it will shorten the engine life. Is it really safe to do?

Thanks,
IronZ

Which 4-stroke to purchase?
 

The recommendation was from one of their tech personnel I was on the phone with. If you look at the various types of satios you will notice the mention of using 30% Heli fuel and I also think it is refered to in their FAQ. Check out the test on the new satio 100. This is for all of the current generation satios not the older higher compression satios.

Which 4-stroke to purchase?
 

The tests in RCM that I was referring to used Morgan's 10% Omega fuel with 4 ounces of castor oil added during the break-in. This fuel was used for both the Saito .72 test and the OS FS-70 II test.

Clarence Lee also says in the Saito review, "saito recommends using a fuel containing a 20% oil, 10-15% nitromethane, and that straight castor oil should not be used, but a mix of synthetic/castor is ok."

So his recommendation from Saito was for only 10-15% nitro.

Which 4-stroke to purchase?
 

Its really too much to ask anybody knowledgeable to believe a test that a manufacturer does comparing their engine to a major competitors. What would you expect Horizon to say: "Well, we tested the Saito 100 vs. the OS 91 and the Saito was hands down the better engine - of course we are not the least bit biased in any way whatsoever and are completely neutral with no conflict of interest in these matters." Yeah sure.

Re: Horizon says to use 30% ?
 

Go check the adds for the Saito .30 four stroke in RCM when it was first introduced.

They go on and on about how powerful it is for such a small engine and they say and I quote ," it really comes alive when you use 30% nitro fuel"

Clarence sticks with 10 to 15% so he can compare different engines using a standard base line as far as fuel goes.
It wouldn't be fair if he used 30% in a Saito and 10% in an OS then compared the two.

CK

Running Saitos
 

I notice there is a lot of talk about Saitos liking high nitro fuel, at the other end of the spectrum they also like low nitro fuel. I have a .30 in a Sig LT25, a .40 in a RCM 40, .80 in a Bruce Tharpe FlyinKing and a .91 in a Kombat .60, all will run quite well on Fox's 50/50 with 5% nitro.

Which 4-stroke to purchase?
 

All I was wanting to see is what difference the results of the test would be if the fuel baseline were changed. Not everyone is going to run 10% in their engines. Why not run a set of figures for 10%,20%, and 30%. It would not make the results any less accurate. It would actually show the characteristics of each specific engine better. I was refering to horizon's test of the satio 100 for two reasons:

First to say that I like the format of the test better because of the use of mutliple baseline fuels.

Second to show the significant increases available to anyone if they just changed the percent of nitro in their satios. I have noticed a difference in the behavior of the engine and power with just a increase to 20% nitro by using Powermaster YS 20/20 blend fuel.

I was not trying to say to take horizon's tests as fact because I too realize the test might be biased toward satio because horizon markets them.

Engine choice
 

I have both the Saito 80 and an older OS 70 Surpass. Both engines are reliable and have
good power for their applications. I think
it depends on the application you are going to
use the engine in. What are your plans for the
engine? A heavier engine can be used to help
obtain a proper balance on your plane etc.

Good luck Sam