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FSa-72II 4-Stroke Engine

For you glow pilots we have a story about he upgraded FSa-72II motor from O.S.


60-size plane 4-stroke authority!

From O.S.

Sport flyers will enjoy greater performance, while scale pilots will experience more realistic flight. Everyone will benefit from the FSa-77II's deep, rich sound. The cost for this unit is $479.99.

Upgrades make the popular FS72-a

  • Blow-by oil exits through the breather nipple on the back plate, for more stable operation
  • Black rocker covers gives this engine a more impressive appearance
  • The F-5030 silencer can be positioned to achieve the ideal fit
  • Mounts in the same space as the FS-72a with no modifications required

SpecificationsParts Listing

  • Stock Number: OSMG0878
  • Displacement: 0.72 cu in (11.79 cc)
  • Bore: 1.063 in (20.7 mm)
  • Stroke: 0.811 in (20.6 mm)
  • Practical rpm: 2,400-12,500
  • Output: 1.2 ps/1.18 hp @ 12,000 rpm
  • Weight w/muffler: 18.7 oz (530 g)
  • Includes: 61N carburetor, F-5030 muffler, Type F glow plug
  • Recommended props: (Sport & Aerobatic Scale) 12x7, 13x6-8, 14x6-7

Learn More

Head over to the O.S. site to learn more!

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Sep 05, 2017, 12:55 PM
Registered User
I TOBOR's Avatar
Blow-by oil exits through the breather nipple on the back plate, for more stable operation

If this is true, that is good news, I have a .56 Alpha mounted on an RCM 40, it hesitates every minute or so to the point of almost quitting then blows gray/white smoke and continues on. I placed a vent in the backplate and no more problem, honest.
Sep 05, 2017, 01:34 PM
Making Friction Work
Gary Cee's Avatar
That is how I felt early on when Saito moved some of the case vents from the rear to the oil-starved front cam and bearing area. We had already been moving it for a while before Saito made the change.

Nothing like vindication from the people who make em..
Sep 05, 2017, 01:47 PM
The great Brutifier
Shouldn't that bore figure be something like 25 or 26 mm instead of 20.6?

A bit of a pity that this engine is so high strung for RPM. Lot harder to get it quiet again....
Sep 05, 2017, 01:56 PM
Club Saito | Genesis 8:11
Bunnyshooter223's Avatar
Ah! Maybe the specs are off....

For comparison:
Saito FA-72(A?): 1.2hp, 11.8cc, Bore x Stroke = 27 x 20.6
Sep 05, 2017, 02:41 PM
Registered User
I TOBOR's Avatar
1.063" are equal to 27.0002mm
Convert length: 1.063 mm (millimeter) to ...
Sep 05, 2017, 03:17 PM
Registered User
Looks like a nice engine but at that price, no thanks.
Sep 05, 2017, 06:13 PM
Mumbling in the corner.
flyboy2610's Avatar
Originally Posted by GRANT ED
Looks like a nice engine but at that price, no thanks.
You got that right!
Sep 06, 2017, 06:39 PM
Registered User
I absolutely love my FS-72a engines and can't get enough of their purr in the air but the $100 premium for the mkII version is enough to push me away. I'm lucky enough that the price really doesn't matter but I'm not in the mind to put a $500 (yes, I know it's really $479 but my mind is rounding up to $500) engine on a plane that size. I'll just go to a bigger plane and get $500 of gas engine and nice quiet pipe.
Dec 10, 2018, 06:26 PM
Professional farm-buyer
Interesting they added the crankcase breather......I wonder why? I've heard mixed things about the Alpha series engines when side mounted, but it seems to be on a case by case bases.

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