Because of financial restraints I cant go with the Saito or the OS .75 AX I would really like. What do you guys think of these motors for the Hellcat. I Plan on using a a Pitts Style Muffler. The manual actually calls for a Saito 100 or a Evo .61. Thanks


Option 1

GMS .76 BB Ringed Remote Needle Valve w/Muffler $99.99

Output: 2.5 BHP at 15,000
RPM Practical range: 2,000 - 13,000 RPM (with 11x7 prop)
Weight: 19.4oz (550g) without muffler
Sport Model: 12x6
Racing Model: 11x8
Scale Model: 13x6



Option 2

Tower Hobbies .75 Ball Bearing ABC Schnuerle & Muffler $89.99
2.2 BHP at 15,600 RPM
Weight: 535g (18.9 oz) (without Muffler)
Recommended Props: Break In: 12X6 or 13x6
Practical RPM Range: 2,000 - 16,500 RPM


Option 3

Evolution .61NT Glow Engine w/Muffler $119

Total Weight: 25.44 oz
Benchmark Prop: 11x7 @ 13,000 rpm
Prop Range: 11x7 - 12x6
RPM Range: 2000 to 13,000

I Fly the H9 Corsair & H9 Texan with the Evo .61 with pitts mufflers. They fly very well but a little more power wouldn't hurt. Check into the Magnum .91 4 stroke. very well priced & should be a good engine.

Thanks for the reply. The Hellcat seems like it would be about 1lb heavier. I would really not like to spend more than $100 or so on the engine. I would also like to stay with a 2 stroke.

Option 1 & 2 are effectively made by the very same company.

There are only a few cosmetic differences between the two engines, but the GMS has the slightly larger bore.

All three can be a handful to get running & tuned initially, yet I've had one of each start right up out of the box and then only need a click or two of adjustment.

My out of box experience has been mixed.


The Evolution should have it's blue limiters RIPPED off when you get it.


Knowing all three, I favor the GMS for it's slight power advantage and the T.H. for Tower's parts stocking. ( It's a snap to get something sent to you quickly when you need it. ).

Both engines would work well, and mufflers, etc. are interchangeable between the two.

My BIG grip with the two engines is the placement of the muffler bolts.

Many engines have you screw in the cap screws into the muffler from the opposite side of the cylinder head.

In the .75 TH and .76 GMS, you need to do this from the same side as the muffler. The screws affix into the cylinder head instead of the muffler.

The problem is that there is not much clearance there, so if the engine is cowled, things get problematic.
You must use the supplied allen key ( and hopefully NOT loose it! ) or cut down your own. Even with the shorter key this arrangement is still annoying.

I don't know which Pitts muffler you are looking at, nor how you will be accessing or mounting this, just be aware of the cap screw matter.


Remember though that the weight may also force you to do some redistribution of components, since the 2 strokers are going to be lighter.

Thanks Jose, great info !

I own or have owned most of the 2-stroke .91s. Right now I have a Magnum .91 2 & 4-stroke, 2 SK .91s and a Tower .75.

Tower .75:$90 bucks. Tons of power at high rpm. Likes a small prop. Would not be my choice for a radial cowled plane. The GMS is made by the same company in China, but has a Dykes ring. Needs a break-in for that type of ring. The Tower is easy to hand start and tune if you are familiar with Chinese engines. Most people make adjustments too large.

Magnum .91 is over $100, but a great engine. The 2-stroke has a good bit more power than the 4-stroke, which is a clone of the OS. I used an Ultra Thrust tuned muffler on a couple of planes and turned 12,000 on an APC 14-6 on 10% fuel. Very easy starting. This would be my second choice.

SK .91: $100 bucks. This would be my choice for a radial cowl. Ported for torque and large props. Very hard material and needs a good break-in. A 15-6 is the smallest prop that will run well. Smaller ones will lean out. I love this engine for big props. Break it in per their instructions and it is a tractor on big props. Try a 14-6 and it will lean out and fry in the air. Check the SK thread in the Engine Forum. They (at least my two) are easy to hand start, idle well, have a good mid range and hold top end on a big prop well. Excellent carb for function, although mine had burrs on the diagonal cut in the rotating barrel that I had to smooth out with a small file. I estimate it was from a dull cutting tool.

So you would recommend a .91 for this 60 size plane? The manual recommends in a 2-stroke a 60–.78... Also, wouldnt a 14" prop be too big for this plane?

A 2 Stoke .91 is going to give you gobs of power, but cowl clearance and prop clearance may indeed be an issue.

When a model is unknown to me and I'm going 2 stroke, I always go with the biggest recommended engine.

That way I know it will fit.

You are NORMALLY OK going larger, but there are always exceptions...

Frankly in the 2 stroke world, I've never been unhappy with the largest recommended size.



I can't say the same for 4 strokers though, as I always wish for a bit more power than the largest recommended or I end up with an oversized engine.

e.g. a 1.40+ in a plane that calls for a 1.20 FS etc.

Yeah, It recommends a .61 to .75 2 stroke, so I think I'm going to go with a GMS .76 a Bisson Pitts Muffler and and play around with the APC 12x6 maybe 13x6. My buddy has a h9 p-47 and runs an .65LA and it moves it pretty good and its also heavier. The LA outs out 1.7 and the .76 puts out 2.5. It should fly nice....