Conversion - 1/2 Mosler

Rev - Nov 11, 2017

 By Jan Zumwalt (EAA #66327)


Fig-1: Mosler installed on aircraft, and the inside of the engine case

See Also


Mosler engines are 1/2 VW aircraft engines by Mosler, Inc. of Hendersonville, North Carolina. This firm was owned by Warren Mosler, a well-known custom automobile manufacturer in Riviera Beach, Florida. Mosler, Inc. bought the engine assets of Global Machine Tool in 1986 and introduced their own engines in 1987 . Mosler, Inc. also bought the assets of HAPI in 1989. Mosler engines were assembled from component parts built by other manufacturers. The firm later became known as Total Engine Concepts (TEC) and relocated to Riviera Beach, Florida. TEC dropped the sales of VW parts and engine conversions in early 1998.


The CB-40 was re-engineered to overcome problems of vibration and cooling in the original design. Suited for ultralight use and single seat light sport aircraft, the engine weighs 86 lbs and produces 40 hp (30 kW). The engine uses a short aluminum crankcase with redesigned oil galleries for improved lubrication. The engine is counterweight balanced with a drop-forged crankshaft.


MM CB-40
General characteristics
Type: 2-cylinder air-cooled horizontally opposed aircraft piston engine
Bore: 3.701 in
Stroke: 3.071 in
Displacement: 66.1 in³
Dry weight: 86 lbs
Fuel type: 100LL avgas
Cooling system: Air-cooled
Power output: 40 hp at 3250 rpm at sea level
Compression ratio: 8.94:1


By dick Cavin - Sport Aviation, April 1989

The N3 Pup is a popular Ultralight for the Mosler Engine.

One of the cornerstones of Industry everywhere is the American truism, "Necessity is the mother of invention." If a need exists, you can depend on someone seeing the potential of solving the problem and coming up with a solution. Such has been the case in the aviation industry from the very beginning. Designers have always said, "Give us a light, dependable engine and we'll design an airframe to match it." History shows a relatively small number of engines, with large numbers of airframe des1gns built around each engine. History also shows us the light plane industry that flourished in the '30s and '40s had 1ts foundations la1d w1th the advent of the Aeronca E-113C and Continental A-40 engine sizes of 37 to 40 hp.

These engines made it possible for the masses to have access to really economical flying in the Aeronca C-3s and E-2 Cubs, which flew two people on a miserly 2 gallons an hour or less. A wise man once said that a depression was when people didn't have the money to buy the things they need or want. In light of that fact, it would seem that as far as recreational av1at1on IS concerned we indeed have come full circle and are in a depression. Now, JUSt as it was during the Great Depression of the '30s, there is a great pent-up demand for an entry level airplane that can be purchased and operated on a bare bones budget. In the past few years we've seen a proliferation of affordable designs in the featherweight bracket. In spite of an ever improving record of two cycle dependability,the great masses of potential aircraft owners and pilots are staying away in droves. The major reason is Simply fear, an innate distrust of two cycle power (whether deserved or not).

The winds of change are blowing, though. As a matter of tact, they have been blowing for over a year in Hendersonville, NC, where Mosler, Inc. IS busily cranking out a gutsy little four cycle. precision built power-plant that delivers an honest 40 hp at 3250 rpm. Like the Aeronca and Continental engines of the '30s, this little smoothie just "sips" fuel at a miserly average rate of only 1.8 gal per hr. at cruise rpm. The predecessor of the Mosler MM­ CB 40 hp engine was the Global 35 hp engine, which had a number of problems that, along w1th under-capitalization, probably resulted in the demise of the company. The problems were vibration, unreliable oil pressure, inadequate cooling and porosity of some crankcases.

Heritege - Global Engine

The Global engine was the standard power-plant for the Nostalgair N3 Pup ultralight, a fine little 3/4 scale version of the J-3 Cub. The corporate structure of Nostalgair became intertwined with GlobalMachine Tools and when Global temp, it also shows torque, horsepower, the amount and pressure of intake air and exhaust. It will even automatically shut the engine off if any reading exceeds programmed limits. At the end of the two hour test, the engine is a proven quantity and the builder can go fly it with confidence. All external nuts are then re-torqued before the engine is put in its shipping container.

Flexible exhaust stacks are attached for the run in and they feed into mufflers, so permanent stacks are now attached. Break in oil is then drained and new oil added. Finally, the engine is wrapped in plastic and put in its shipping box, completely surrounded by an expandable foam for shipping protection. Dry weight of the engine is an impressive 86 lbs. which includes the oil cooler. With its compression ratio of 8.94:1 it can use either avgas or auto fuel. When one compares the MM-CB's installed weight with a comparable two cycle engine (with muffler) there's not much difference, but fuel and oil savings over a 500 hour period are significant, amounting to several hundred dollars.

Mosler Buy Out

To the credit of the Mosler company, they are sending an MM-CB engine to all former purchasers of Global engines who failed to receive their engines before Global went under, even though they are not legally obligated to do so. They are doing this through diversion of royalties from the sales of N3 Pup aircraft. For every five airplanes sold, the company will send an engine to the next customer in line, as determined by order date. Now, all that remained was the proof of the pudding - in the air. The next morning dawned much calmer with only a 15 kt. wind, down the runway this time, and a cool 50 degrees. We were at the airport just after daybreak so we could fly before the wind came up to its forecast of 25 kts. later. I chose to fly the ultralight Pup first and, incidentally, it was the same Pup I flew nearly 4 years ago.

Mosler and the N3 Pup

Getting into the N3 Pup is easy. You just back in, sit down and turn around. It's comfortable inside. There's plenty of headroom for even bean pole types, and it's plenty w1de (about 23" inside). There's lots of leg room, also, maybe almost too much for small people. One enters the Pup on the left side. S1nce the prop turns clockwise, one can stand alongside the airplane on the left. flip the prop with the left hand and handle the throttle with the right. Like most ultralights, the Pup gets off a second or so after you get the throttle open, 1n maybe 200 ft. or less.

At 50 mph it climbs quite well. about 700 fpm I'd guess. At its cruise speed of 60 mph lAS, its control pressures are light and well balanced. In turn entries I found much less adverse yaw than a J-3 Cub has, probably because of the modified Frise aileron design. The airplane slips beautifully, too. Oh, yes. I got so much fun out of flying the airplane that I forgot to notice how smooth the engine was until then. It was even smoother than it was on the ground. clear down to idle rpm! The N3 Pup supposedly will stall at 28 mph, but I could never get it to stall - only mush below 35 mph with idle power.

Parts inventory                                                          Engine Assembly

Weighing connecting rods                                                          Engine test cell operation

That Gottingen 387 airfoil hangs on and hangs on. The Pup is "open air and it got nippy that morning, but if a person wanted to go over the ultralight lim1t and make it experimental. he could add Windows, a D cell leading edge, a bungee gear, brakes, wheel pants, floats, or a dozen other extra we1ght items. That's basically what they have done with the Super Pup, plus clipping the wings to a 26' span. Leading edge wing tanks are added to raise capacity to 12 gallons. After I got down with the Pup,the two place N3-2 was all warmed up and ready to go. I crawled in the back seat, which is about where the baggage compartment would be on the N3 Pup. Getting in the front seat takes more doing for a big old fellow with arthritic knees, but would be easy if the back of the front seat was made removable or foldable (and that project is on their "must do" list).

Both seats are snug, but reasonably comfortable. The two-place weighs 350 lbs. empty and grosses at 800 lbs. We were carrying 450 lbs. of useful load with slightly over 5 gals. of fuel. The wind had come up a bit - to about 20 mph - and I estimated our take-off run at about 600 ft. Surprisingly our rate of climb was almost as good as the ultralight, an estimated 600 ft./min. It flies almost identically as the ultralight, except it is even more docile at low speeds and hangs on and on with full aileron control and will only mush at 35 mph. The wing is sized identically with that of the ultralight (30.5' span) except a little more beef has been added in frtlings, etc., to bring it up to 6.25 G capability like the N3 Pup and Super Pup. Apparently the same Gottingen airfoil really ''loves·aft CG (we were at 35%}. That in combination with about an up· ward 10 degree reflex on the last 1nch of the ribs, seems to really make the N3-2 into a real pussy cat, a great litt1e trainer.


The wind was gusting to 25 kts. when we landed,but was no real problem and our landing roll was only about 200 ft. The bungee gear, of course, makes for a smoother, softer touch down than the ngid gear on the ultralight. The N3-2 is 4" longer than the N3 Pup.The tandem throttles were located above the left door sill, but could be located on the right side at elbow level. The door could easily be put on the right side if the customer preferred. Time and space do not permit our going into greater detail on construction details on all three Pups except to say that they are all well built little airplanes. built much like the J-3 was, with extruded alum1num spars, stamped aluminum ribs and a welded steel tube fuselage. They fly very well on 40 hp and are competitively priced from $7995 to $9995.In my op1nion, they and the engine would make an enjoyable and dependable little sport airplane. I also feel the N3-2 will make a gentle and forgiving little trainer and perhaps become one of the classic designs.