southern_touch9

My Feedback: (3)

I am currently in the market for a motor that puts out around 3 HP. I have been looking at the O.S. 1.08. I have seen these motors run I am impressed. The price tag is $250. I scroll down and see a GMS 1.20 BB for $150. The weight is the same as the O.S. and the GMS 120 puts out 3.3 HP. Whats the deal on these GMS motors? Has anybody run one yet? If so were you impressed.

I would be putting this motor on a High performance airplane, and I expect it to have unlimited vert. (The plane will weigh in at 8lbs). Will the GMS do the Job?

twostroker

My Feedback: (37)

GMS, have three, like them very much. They are still being overlooked in favor of more popular brands, but they are great quality and powerful. I think the horsepower rating for airplane engines is bull, but these engine have the same or more HP than the popular brands. The engines in my hanger are the 47, 76, and 120.
Tim

John Hawkins

My Feedback: (2)

Just came in from running my new GMS 120 in and so far I am impressed. It has 40 ounces through it as is coming around very nicely. In fact I feel confident about putting it in a plane right now. I used 15% Omega with some extra castor and an APC 14 x 10 which was cut to about 13/14 (pavement grinder ) It is idling at near 2000 and transitioning well to 9500. Mid range seems good. I am rich on the top. I peaked it briefly at over 10k. It hand starts easily with often just a single flick. I have a pumped OS1.08 and the GMS is a significantly more powerfull engine by my reckoning.

I took the back cover off before running and it was clean of any debris inside. While I tightened everything, and it was fine, I'm not sure I checked the throttle arm. In any case it came off and went into the prop. Where it is now is anybody's guess. I cobbled one together as you can see in the pics which allowed me to finish the fuel I had in the jug.

I have an ASP carb from a 1.08 and it would have fit but the bore is around 11mm while the GMS is 9.5. With the ASP being famous for poor fuel draw I gave it a pass. The muffler is a Bisson.

John Hawkins

My Feedback: (2)

Carb arm quickly cobbled up: A 5/16 nut was drilled and tapped for 4-40. I used a control horn on a SHCS to act as a combination horn and rotation lock. Rather than order a new arm I might modify this so that there is a separate set screw to position the arm and another out at angle to get more clearance away from the engine for the horn. This one would be peened or brazed against turning. The horn makes the arm adjustable too. Don't know if I would get warranty on the lost arm although I think rightly one should.

John Hawkins

My Feedback: (2)

A couple other notes: The main needle turned on its own from vibration going toward lean. I bent the spring and it is holding it for now but I would be concerned that it might not continue to. I think I'll put some tubing around it when it goes in the plane. A minor point; they don't give you a set screw for the main needle extension unless mine was missing. It might be fun trying to find one of those at the LHS.

The test stand is screwed solidly to the heavy plank stairs. Don't know that the wife will be real impressed with the mess of oil.

Time to go pack it up. This engine looks very promising at this point.

RJConnet

I love my GMS 1.20's, Just had to buy a second one after I ran the first one for a while. They both start easy and they run till you shut them off. They are very user friendly. I have one on a GP G202 and the other on a Stinger 1.20, vertical is not unlimited on either one but is plenty good enough for me. They both turn an APC 17-6 at 8600 to 9000 RPM depending on weather, fuel, and Etc. When you take one out of the box put a plug in it and turn it over you will say man, where is the compression. Never mind, it has a Dykes ring and the static compression will never feel like an ABC engine, but they just run great. Got mine for $130 bucks each and got rid some old junkers in the process (Mecoa RJL).
Do you get the idea I like mine?

RJ

southern_touch9

My Feedback: (3)

I get the idea.

Roughly how much does your stinger 1.20 weigh?

RJConnet

About 12.5 Lbs. It could be lighter but I made no attempt to build it light and it is covered with cloth and dope.

RJ

southern_touch9

My Feedback: (3)

so if the airplane that I am putting this on weighed about 8 lbs (with the motor and radio gear) you would think that I would be abel to sustain hover?

georgehere

Dumb question, Mr. Connet, but why does everybody run a Pitts muffler on the GMS engine? Or is that what comes with the engine? Thought the Pitts was for a cowled application. Just curious.

RJConnet

Southern,

Yes, my GMS engines pull about 12 to 13 Lbs. static thrust with the APC 17-6 prop so an 8 Lb. plane would be duck soup.

George,

There are no dumb questions, Like a lot of the big bore 2-strokes (Moki, Webra and so on) it does not come with a muffler and most of us like the pitts for use in cowl. I just don't have the cowl installed in the picture in post #6.

RJ

southern_touch9

My Feedback: (3)

? I didnt know cuz I always run Saitos or YS (in the glow type of motor). Right now its a battle between this motor and a Saito 1.00. This motor seems to have equal or a tad more static thrust than the Satio 1.00. I have just heard a few bad things on here about the GMS 1.20 so I didnt know.

w8ye

My Feedback: (16)

Most of the GMS engines are highly tuned. The GMS 47 is one of the more powerful 46 size engines around. The 61 and 75 are pretty strong too.

The 120 is more mildly tuned. It is no slouch but is not oustanding above all other 120's like the 47 is around other 46's.

Everything that people have posted so far goes along with what I've seen about the engine. It is generally a likable easy to start and set engine. Especially the price.

Don't forget about the Dykes ring when you first get it.

Enjoy,

Jim

georgehere

RJ. . .So if you go to buy a big bore engine, you have to factor in the cost of a Pitts or some other muffler. Did not know that. Thanks.

inter

Not always true!

I believe the Magnum 1.20 gomes with a muffler and a better buy, IMHO.

Not sure about the 1.20 size but my GMS47 is ok. It hates to run inverted, low neddle is only 3/4 turn out from completely closed. Other than that, it is very strong and never deadsticks.

John Hawkins

My Feedback: (2)

Here the Magnum is $110 Cdn more than the GMS. Very often the stock muffler is not suitable for the particular installation and you have to buy another one anyway. I just bought a GMS with a Bisson Pitts muffler for $70 less in total than The Magnum.

tigil

12, 13 pounds its not to much for an engine of this size; a straight OS surpass 120 pull more than that

Broken Wings

My Feedback: (20)

Mecoa's got a close out on all GMS inventory. New GMS 120 ringed engines for $79.99 less muffler/carburetor. I don't know if that's a deal or not.... http://www.mecoa.com/modelerdirect/index.htm

jeffie8696

Check out the Aviastar line.