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OS 2.00 Four Stroke Engine Review

Rich Noon tests OS's amazing new 2.0 powerhouse four stroke!

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Introduction


Stock Number:OSMG0980
Displacement:1.98 cu in (32.4 cc)
Bore:1.197" (30.4mm)
Stroke:1.13 in (28.6 mm)
Practical RPM:1,800 Ė 10,000
Power Output:2.9ps/9000 RPM
Weight of engine:30.68oz. (116g)
Propeller:15x12 thru 20x8
Crankshaft Thread Size:5/16-24
Manufacturer:O.S. Engines
Available From:Tower Hobbies
Approximate Price:$499.98

The newest and largest in the Surpass line is a perfect power plant for any 1.50-1.80 size plane!

O.S Engine's latest addition to their FS series engines!

  • Ideal for scale and sport aircraft
  • 80N carburetor can be reversed 180į for easy adjustment
  • F-6010 silencer for mild 4-stroke sound
  • Glowplug: O.S. #4 supplied with engine
  • Warranty: Two-year limited

First Look

OSís new FS-200S came in the OS blue box with their usual quality packaging. As I unpacked the box, I was impressed with the finish and size of the new engine. There was no damage and the finish was perfect.

At first, I thought this couldn't be a 2.0 displacement engine. It was way too compact and light. Amazing!

Innovations

Here's a photo overview of this innovative engine:

SPECIFICATIONS

Dimensions:
Crankshaft Thread Size:5/16-24
Distance from Carburetor to end of Crankshaft:6.8" (172mm)
Distance from Crankcase Center to Prop Hub:3.03" (77mm)
Distance from Prop Hub to End of Crankshaft:1.45" (37mm)
Distance from Carburetor to Crankcase Center:2.3" (58.5mm)
Distance from Carburetor to Prop Hub:5.3" (135.5mm)
Distance from Center of Engine to End of Crankshaft:4.48" (114mm)
Height from Crankshaft Center to Rocker Cover:4.68" (119mm)
Height from Crankshaft Center to Muffler Center:3.2" (82mm)
Height from Crankcase Bottom to Rocker Cover:5.7" (144mm)
Width at Mounting Tabs:2.6" (67mm)
Width of Crankcase Below Mounting Tabs:1.9" (48mm)
Width of Cylinder Head:2.2" (58mm)
Distance Between Mounting Holes Same Side:0.98" (25mm)
Distance Between Mounting Holes Opposite Side:2.3" (58mm)

ComponentAdvertised WeightActual
Engine1.83 lb (830 g)1.9 lb (862g)
MufflerNA4.1 oz (116g)
Total:NA34.49 oz (978g)

Quick OS 1.20 and 2.00 Comparison

I set my OS 1.20 FS on the bench next to the OS 2.00 to compare the size difference. Considering the 2.0 is almost twice the displacement, its compact size and similarity to the 1.20 footprint is amazing!

Advertised specifications: FS-200S FS-1.20E
Displacement: 1.98 cu in (32.4cc) 1.218 cu in (19.96cc)
Horse Power: 2.9ps /9000 RPM 1.9 /11,000 RPM
Crankshaft thread size: 5/16-24 5/16-24
Bore: 1.50" (38.0mm) 1.22" (30.4mm)
Stroke: 1.13" (28.6mm) 1.08" (27.5mm)
Distance Between Mounting Holes Same Side: 0.98" (25mm) 0.98" (25mm)
Distance Between Mounting Holes Opposite Side: 2.28" (58mm) 2.28"(58mm)
Distance Center of Crankcase to Drive Hub: 3.03" (77mm) 2.99" (76mm)
Width Between Mounting Tabs: 2.6" (67mm) 2.6" (67mm)
Width of Crankcase Below Mounting Tabs: 1.9" (48mm) 1.77"(45mm)
Length of back of carb to drive hub: 5.33" (135.5mm) 5.03"(128mm)
Height/Bottom of Crankcase to Top of Cylinder Head: 5.7" (144mm) 5.45"(138.5mm)
Weight: 30.68oz (116g)w\header pipe 30.5oz (864g)

First Run

It was around 75 degrees when I arrived at my test stand. I bolted the engine to the stand, and mounted the Top Flite 18X8 I planned to use for break-in. I filled the tank with Byron 15% fuel and was ready to fire it up!

After opening the high speed needle four turns, I spun the engine a couple times by hand to prime it and hooked up the glow driver. I thought I'd try my usual method of starting big four stroke singles of spinning the prop backwards against compression with a chicken stick. It immediately fired and kicked the prop nut loose enough to freewheel the prop! And believe me the prop was tight! I thought, "Ok, we won't be doing that again!Ē

After re-tightening the prop, I hooked up my Sullivan Dynatron Starter. A quick bump of the Sullivan starter and the motor was purring. I followed OS's recommended break-in procedure of leaning the engine for five seconds, then richening it to let it cool. After four 10 oz. tanks, I leaned it out and checked RPM and transition. It was spinning the 18x8 prop at 7620 and idling smoothly at 2160. Transition was excellent! I never did have to adjust the low speed needle through all the test runs.

I've owned and flown quite a few large displacement four-stroke engines., and all of them tended to vibrate and were rather noisy. Through all the OS 2.0's test runs, I was really impressed at how smooth and quiet the engine was for such a powerful large displacement single.

My test stand is on the edge of a small patch of wood, and my son ďassistedĒ me with the testing. He made the comment that the prop wash was moving the leaves on the trees 30 feet behind us!

Downloads

RPM Readings

I always figure around two gallons of fuel for break-in for a four stroke engine before trying to achieve top RPM, and I usually assume performance will increase with each tankful of fuel. But the following figures were pretty impressive!

PROPWOT RPMIDLE RPM
Top Flite Power Point 16X88,6202160
Top Flite Power Point 18X876202160
Top Flite Power Point 18X106,8902040
Top Flite Power Point 18X1262702040
Top Flite Power Point 20X6-1056602010
Top Flite Power Point 20X863001920
I'm sure RPM readings will increase as the engine continues to break-in.

PROPStatic Thrust at WOT
Top Flite Power Point 16X813.68 lbs.
Top Flite Power Point 18X817.13 lbs.
Top Flite Power Point 18X1014.0 lbs.
Top Flite Power Point 18X1211.6 lbs.
Top Flite Power Point 20X817.85 lbs.
Top Flite Power Point 20X6-1014.1 lbs.
Computed using the ThrustHP static thrust program

Sound Levels

IdleWOT
65db.92db.
Readings taken at app. 6 feet with a Top Flite Power Point 18x8 prop installed.

Conclusion

The OS 2.00 is a powerhouse, on a small footprint with an impressively quiet muffler for its size! It's size and power makes it a good fit for a broad range of sport and scale models, and it should be another big seller for the already famous OS lineup.

Pluses:

  • Excellent manual
  • Easy break-in and setup
  • Awesome torque
  • Quiet muffler
  • Great transition
  • Low vibration
  • Compact footprint

Minuses:

  • None noted!

I believe OS has just set the bar a little higher for large bore single cylinder engines. I sure can't wait to get her flying!!

Last edited by Angela H; Jun 25, 2007 at 02:20 PM..

Discussion

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Old Jun 28, 2007, 11:27 AM
Grumpa Tom
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United States, CA, Los Angeles
Joined Sep 2003
23,598 Posts
Love the engine reviews! Keep 'em coming!
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Old Jun 28, 2007, 01:46 PM
Right Honorable Member
flatfour's Avatar
Chicago Midway, Illinois, United States
Joined Jul 2003
517 Posts
The review mentions a #4 and #8 glow plug. Does this engine not use the "F" plug?
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Old Jun 28, 2007, 02:31 PM
S.A.D. member
ivanc's Avatar
United States, TX, Round Rock
Joined Dec 2004
9,420 Posts
Quote:
Originally Posted by flatfour
The review mentions a #4 and #8 glow plug. Does this engine not use the "F" plug?
I guess it's a typo. Tower lists it with a F plug included.

Ivan
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Old Jun 28, 2007, 02:45 PM
The sky is my playground.
Dora Nine's Avatar
United States, NH
Joined May 2005
7,676 Posts
Gotta love that sound of a four stroke! Please keep the engine reviews coming!
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Old Jun 28, 2007, 06:36 PM
Registered User
I TOBOR's Avatar
Joined Feb 2007
2,797 Posts
I don't know where that guy has been but a Saito 1.80 on its worst day will slaughter that thing.
Saito 1.80 & APC 16x8==9,500 rpm
Saito 1.80 & Graupner 16x8=9,400 rpm
APC 18x6W==8,900 rpm
Menx 18x6 on 10% nitro==8,600
My own lowly Saito 1.50 turns an 16x8 Graupner at 9,000 on 15% PM
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Last edited by I TOBOR; Jun 30, 2007 at 06:25 AM.
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Old Jun 28, 2007, 07:46 PM
Registered User
United States, CA, Burbank
Joined Jul 2004
79 Posts
Where are the comparisons?

What good is an engine review without comparisons to competing products. How does it compare to the Saito 1.80 and 2.20? It's nice to know that it runs smoothly and doesn't make too much noise, but if I'm going to spend $500 for it, I want to know whether it is in the same league as the competition powerwise.

And if it isn't, you owe it to your readers to say so.

Jim
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Old Jun 28, 2007, 08:59 PM
The reviewer
XJet's Avatar
Tokoroa
Joined Mar 2004
3,827 Posts
All reviews should include the following information:

1. was the engine purchased by the reviewer or supplied by the manufacturer or publisher?

2. if the engine was supplied by the manufacturer/tester, was it returned after the testing was completed or was the reviewer allowed to keep it?

3. What frames of reference does the reviewer have when drawing conclusions and rating the various aspects of the product?

4. Does the publisher accept advertising from the manufacturer or distributor of the product being reviewed?

These, and many other factors can sometimes influence the outcome of a review and unless we know the facts we can't judge just how objective the review might be -- hence it is worthless.
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Old Jun 28, 2007, 09:48 PM
Canucklehead
orenda635's Avatar
GTA, Ontario, Canada
Joined Apr 2004
827 Posts
I like what they've done with the muffler. Still, this engine is a little on the expensive side. A comparable gasoline engine such as the Evo 35GT2 is $50 cheaper and is also more economical to run. Even the Evo 26GT2 would work for models in that range and it's a full $100 cheaper. Once models get over 1.20 size, glow starts getting impractical simply because of the cost of fuel.
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Old Jun 29, 2007, 05:51 AM
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I TOBOR's Avatar
Joined Feb 2007
2,797 Posts
My main concern is its obvious lack of power, nobody is going to spend $500 bucks for a 2 cu. in. engine with the power of a competitors 1.50 fourstroke.
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Old Jun 29, 2007, 06:39 AM
Registered User
Joined Apr 2007
6 Posts
Os 200

Well i dont know what he did to get those numbers but mine did (After 2 gallons) 9100 on apc 18*8 (Jero Helimix15/20)

This cant be right or maybe a bad wolf???
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Old Jun 29, 2007, 08:20 PM
Registered User
United States, CA, Burbank
Joined Jul 2004
79 Posts
Quote:
Originally Posted by XJet
All reviews should include the following information:

1. was the engine purchased by the reviewer or supplied by the manufacturer or publisher?

2. if the engine was supplied by the manufacturer/tester, was it returned after the testing was completed or was the reviewer allowed to keep it?

3. What frames of reference does the reviewer have when drawing conclusions and rating the various aspects of the product?

4. Does the publisher accept advertising from the manufacturer or distributor of the product being reviewed?

These, and many other factors can sometimes influence the outcome of a review and unless we know the facts we can't judge just how objective the review might be -- hence it is worthless.
Well, I am reasonably certain that the importer gave it to him, he gets to keep it and the importer is a major advertiser. But it didn't seem to make much difference. That review is certainly not going to sell many engines.

Jim
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Old Jun 29, 2007, 08:41 PM
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Joined Feb 2007
2,797 Posts
Well Jim, maybe its the oilless fuel he ran in it.
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Old Jun 29, 2007, 08:45 PM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
I'm working on my first "big" plane now...a ultrarc katana and I'm putting a 36cc gasser in it. Why would I put a glow engine in it instead? I'm wondering where a glow would be better than a gas engine?
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Old Jun 29, 2007, 08:50 PM
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I TOBOR's Avatar
Joined Feb 2007
2,797 Posts
With me its a personal preference, I'm putting a Saito 2.20 on a 12 foot Telemaster because it just seems wrong to have that big beautiful plane sound like a chainsaw.
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