mlgreene

I’m getting ready to buy a 4 stroke for my U-CAN-DO-3D 40 size airplane (that my wife is getting me for Christmas, good wife). I’m looking at getting either the Saito FA-72 or the OS FS-70 II Surpass. They both look like good engines. Was wondering if there was a reason I should get one over the other. I did notice in one picture of the Saito FA-72 that the back cover with the needle valve looked like it might be plastic. Does anyone know if it is plastic or metal? What has been your experience with either engine?

Mike

tIANci

Mike - its plastic and there is no issue, its hard stuff and only a mere back plate, I got no leaks at all. I think the OS is a 'better' engine compared with the Saito 72 because of the pump but the Saito is lighter.

Pepe J

My Feedback: (2)

Mike... There are both excellent engines. The OS has the edge in power. The back plate on the Saito is plastic. Do a search and find out if and where you need ballast for the CG and select the engine accordingly. The OS is about 3.5 oz heavier. You may want to consider the new Saito 82.

Happy Fly'n...

mlgreene

I was wondering if it was plastic or not. I have an OS .15 that has a plastic back cover and it always has some bubbles coming from around it. I tighten up the screws and it stops for a short time then starts leaking again. Seems to run ok either way.
Both the Saito and OS look like good engines. I did notice the Saito was a lighter engine.
I was thinking it was the OS FS-Ultimate that has the pump?

Thanks
Mike

Pepe J

My Feedback: (2)

A little high temp silicone will solve your leaky .15 back-plate problem. A little on the screw threads should retain the screws or Blue Loctite. Put the silicone your back-plate and not the engine case, this way when you put the back-plate on the silicone is less likely to get in the engine case.

You're correct. The Ultimate is pumped version of the 70 and a totally different animal from the Surpass series.

Happy Fly'n...

Pepe J

My Feedback: (2)

A little high temp silicone will solve your leaky .15 back-plate problem. A little on the screw threads should retain the screws or Blue Loctite. Put the silicone on your back-plate and not the engine case, this way when you put the back-plate on the silicone is less likely to get in the engine case.

You're correct. The Ultimate is pumped version of the 70 and a totally different animal from the Surpass series.

Happy Fly'n...

Richard L.

My Feedback: (24)

The OS 70 is a stronger runner than the Saito 72 on lower nitro, such as 10% or 15%.

Test005

I run my OS 70-fs II on 15% Byron fuel and it works super.
The engine is great and I couldn't be more happy...It's also super easy to break in and tune.
This is my first fourstroke and when it runs, it makes me look like an old engine-guru
Two thumbs up from me on the OS, I'm getting another OS, the 91-fs II next!

The Saito-OS debate has people on both sides and I think you won't go wrong with either, it's more a personal choice.
Now I have started down the OS route and I'll stay there until I get a good reason not to.

William Robison

My Feedback: (3)

I have dumped all my OS four stroke engines. They did have slightly higher power from a given displacement in some cases, but they are consistently heavier.

The OS 4s engines (until the FL-70) have iron ringed pistons running in steel sleeves. After a few ring jobs you have to change the pistom and sleeve also, as they wear too. In the Saito engines, with the chrome plated sleeve, I've never had to change either a piston or cylinder sleeve.

If you don't put a lot of time on your engines either will do well. If you fly a lot, the Saito will give the lowest overall cost of operation. The OS parts are very high priced as well. When it's piston and sleeve time replacing the engine instead of repair is a close call.

Bill.

Hobbsy

My Feedback: (102)

I crashed my first Saito .72 into the middle of a concrete road, the crash made the Tru-Turn spinner look like a sunflower, bent the crank and sheared the highspeed needle off, the backplate did not break. WR now has that engine to bone out for parts. I now have another Saito .72, I wouldn't be without one.

William Robison

My Feedback: (3)

Hobbsy's old FA-72 did not get parted out. With a new crank it's perking along quite happliy.

Bill.

Flyboy Dave

My Feedback: (21)

On the other side of the coin, I dumped my Saito's....don't like them. []
Way too expensive....the parts are dear as well.

I have a couple OS, 6 Magnums, and 4 YS. Believe it or not, the YS are the
easiest to operate....you just set the needles to spec., and enjoy....no tuning
or fussing around. The Saito was too fussy. I never bothered to mess with the
Thunder Tiger line.

FBD.

Pilotsmoe

well, 4-strokes don't rely on crankcase pressure like 2-stroke engines do, so even if the plastic backplate cracked, it shouldn't cause any problems except maybe an oily plane(blow-by shooting out).

Pilotsmoe

yea, I just did the same thing with a new magnum .91 4-s. Elevator clevis let go, and plane was destroyed( no piece bigger than 6"). Just baught a new crank, and it ran fine. This engine does not have that much run time on it, maybe 1/2 gallon. I was lucky that the crankcase didn't crack. It was a hard crash(just a busted head fin).

Ed_Moorman

My Feedback: (1)

If a .46 balances the plane correctly, then so will the Saito as they weigh about the same. The OS is heavier.

As for the UCD 40, run some weed eater line around the stab tips, fin and lower fuselage. They have had a problem with the tails coming off. One at my field has had his break and the rear fuselage break. His is Thunder Tiger .46 powered and he's a scale flier who just flies it around like a sport plane. (That's probable the problem-it needs the sticks banged around to wake it up). But seroiusly, the wood was very soft on his stab and rear fuselage. The light, white color weed eater line weighs next to nothing and will keep your tail from breaking off.

William Robison

My Feedback: (3)

Crashing a Magnum. I ran out of down elevator attempting a low inverted pass, scattered plane parts for about 100 yards. Magnum XLS engine. Bent crank, half the fins knocked off the head, cracked the case where the carb mounts.

Patched the case, straightened the crank, and didn't worry about the head fins. It's flying again, just as though it had never been crashed.

Bill.

Flyboy Dave

My Feedback: (21)

I stuffed my OS .90 FS straight in, full throttle from about 200 feet
high. It busted the corners off 4 fins, but didn't harm the motor.
The spinner looked like it had been run over by a train.

FBD.

w8ye

My Feedback: (16)

What? Like this? You can see where the crank went through beside the spinner bolt. Bye Bye Y-S 61 two stroke as result of a high speed stall.

nmking09

My Feedback: (61)

I run a FS-70 Surpass I in my .46 UCD, with a 13x4wide prop, and 15% nitro fuel. Pulls that thing around great. It is a slight bit nose heavy (probably because of where the battery is) but it flies like a dream. Can hover at half throttle

William Robison

My Feedback: (3)

Jim:

Send it back to Tru-Turn. They'll fix it for you, and it will cost exactly the same as a new spinner.

Haw.

Bill.

mlgreene

Nmking09
I was wondering how the CG would be with an OS FS-70 surpass. I had done a little research on the u-can-do-3d .46 and a lot of people seem to be using .91 and 1.00 size engines and say the CG was ok with these larger engines. They seem like they would over power the u-can-do but I guess you can throttle back. What size battery pack you using and where do you have it. I would rather have it a little nose heavy than tail heavy.

Thanks
Mike

William Robison

My Feedback: (3)

Mike:

Warning, sir. Many people are indeed overpowering the U-Can-Do, and many people have experienced airframe failures, too.

Bill.

mlgreene

I'm not going to put anything larger than an OS 70 or Saito 72 4 stroke on my ucd .46. I have a Magnum 52 4-stroke I was thinking about putting on but not sure. I was thinking about getting the Saito 72 but the OS 70 II Surpass looks good too. Not much difference in price between the two.

Mike

smokingcrater

the .72/70 is the MINIMUM you should run on the .46. it will hover on a 72, but not exactly rocket out on the pullout. with a .52 4 stroke it would be terribly underpowered! if you don't already have the engine, go with the saito .82.

blw

My Feedback: (3)

W8YE,

Now I know who stole the photo off of the club bulletin board! To think it was you who blamed Ivan when it blew the shed across the field, thru the fence, across the road, and up into a tree.