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MAICO 760

THE BIGGEST TWO-STROKE SINGLE EVER MADE!

By Rick Sieman

 

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The author spent considerable time extracting the big 760 from deep mud in the Blackwater 100 race."Would you ever go back and try the Blackwater race again on a 760 now that you know what it’s like?"My answer: "No. Not right now, But maybe in a month or so, when the terror starts to fade and I can sleep a full night without waking up in a cold sweat, I might reconsider. But I have learned my lesson. No more 760 Maicos. That just doesn’t make any sense. In fact, I’ve already called the Maico factory to arrange for an 840 Maico for next year. After all, the 920 isn’t ready yet!"Note: For those who want the full, gory, muddy, sloppy, slippery ugly story of the Blackwater race with the 760, you can get it in my book, Monkey Butt, which is available through Off-Road.com.For some reason, the email has increased expressing interest in the Maico 760. So, to satisfy the curious vintage bike historians out there, here’s the test from almost 20 years ago.***Right up front, let’s admit there is no valid reason for this bike to exist. No one in his (or her) right mind needs a 760cc motorcycle for the dirt. Least of all, a 760, two-stroke single.

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Massive fins were actually almost two inches wider on each side than the old 501 barrel which the top end is based on. Weight difference between the two engines? The 760 was only nine pounds heavier.

Everyone knows they can’t work, right? And everyone also knows that the lighter, smaller bikes usually turn the fastest lap times at many tracks. So why does a 760 Maico even exist in the first place?Consider it a noble experiment, if you will. The Maico engineers are a proud, arrogant lot and they love to do things people say simply cannot be done. For example, just a few years ago they made a single-cylinder 125cc road racer that gave the Yamaha twins absolute fits.The FIM made a special class for bikes used in ISDT competition having over 750cc in displacement; this class was dominated by the huge BMW twins. In 1978, Maico decided they could do the Beemers one better and the 760 Maico was born. They fielded a team of tall, strong, German riders and proceeded to get gold medals right and left. The bikes were incredibly reliable and reportedly easy to ride.Still, that was all conjecture, as no one outside of a factory rider had ever slung a leg over one of the beasts. Admittedly, I had a somewhat morbid curiosity and made arrangements to acquire one of the bikes for a test.The basis for the test was when I actually entered and rode the feared Blackwater astride one of the 760s. As luck—and the elements— would have it, I ran out of gas repeatedly and was lucky to finish the grueling event before winter set in. Lack of preparation and endless peat bogs had us well into an advanced state of wheelspin and tree smashing.However, I was left with deep and lasting impressions of the 760. Enough so that I had the bike shipped out to California and put it through the more-or-less normal test sequence.ATTENTION GRABBERFirst off, you must understand that the 760 draws crowds wherever it goes. At Davis, West Virginia, we had a constant stream of folks walking by and studying the big animal. All of them shook their heads in amazement and many of them asked questions. The same questions that we’ll attempt to answer in this test, such as it is.

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Maico East folks delivered the 760 for the race and hung around to help with pit stops after dialing the bike in. That’s Gary Herto with the cowboy hat.

Probably the most commonly asked question was: "Is it fast?"Yes, but not like any Open bike you might be familiar with. It doesn’t explode and lurch off the line, doing wheelstands all over the place. No sir. It merely pulls like the friendliest tractor you ever did see in your whole life.The bike peaks out at a mere 4000 rpm. In this day and age of Open bikes turning 7000-plus rpm, it’s almost leisurely. Peak horsepower is rated at a very conservative 43. However, at a mere 1200 rpm, the massive engine puts out 26 horsepower, more than the hottest 125s produce at peak revs. And we’re talking rear wheel horsepower, too. None of those namby-pamby readings at the crank.Now, think for a moment about those numbers and try to translate them into some sort of reality in your head. It means that the rider can loaf down the trail at just above idle and, with a flick of the wrist, have a big bucket of torque at his disposal. No radical rpm needed. Just roll that sucker on a little bit and get a lot of forward motion in return.To try and give you a good idea of what this feels like, think about the following for a moment. The Blackwater race was held in quite possibly the nastiest conditions imaginable. Deep bogs, tight woods, water crossings of death, etc. Grim. Some of the sections threaded through narrow tree-lined paths, with slippery roots criss-crossing the trails.

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Pipe barely clears the huge head. Horsepower was rated at only 43 at the rear wheel, but the 760 pumped at 26 ponies at only 1200 rpm! That’s barely above idle.

Here, the 760 could be comfortably left in third gear, with no clutch work required.We could let the rpms drop off to almost nothing and smoothly roll the throttle on; the bike would respond by pulling strongly, with no snatching or grabbing. Almost like a Husky automatic, but with none of the irritating lag and hesitation.Long uphills were almost a joke. Just leave the bike in third or fourth and roll the throttle on as needed. No down gearing or clutch slipping needed. This was truly the only dirt bike we’ve ever ridden that never ran out of power, no matter how low the engine was forced to lug and grunt. The closest thing to a tractor imaginable.The second most asked question was: "Is it a bear to ride? Must be a real handful, right?"No. Actually, the bike was incredibly easy to ride. The power delivery was as flat as any stretch of Kansas landscape you can picture. It literally pulled from idle. Now, we know that’s a widely overused phrase, one that journalists like to pull out of their editorial hat to "dazzle the spectators." However, in this case, it holds true right down to the gnat’s buttocks.You can chug the 760 right down to the last few wheezes and it’ll pull back without a hint of protest. There are no odd surges or sudden bursts of power. Rather, there’s a smooth, steady and seemingly endless flow of vibration-free torque. Combined with the heavy flywheels, there’s almost no wheelspin. The meaty Metzeler on the bike simply hooks up and pushes the bike forward with no fuss.NO SHAKES... NO BREAKS

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The 760 required only a blip of the throttle to blast out of deep sand turns. The author demonstrates at the old Indian Dunes track.

You might well wonder how they get a single-cylinder engine of this size to run without vibrating itself to death. Simple. The crank is balanced as if the engine would turn the more-or-less normal 7000 rpm. But, with the power peaking at 4000, the engine never even gets into the shaking range. In fact, it puts out less vibration than a mildly tuned 250 play bike.This leads one to ponder a few things. For example, if the big 760 were allowed to run up there in the high rpm range, what kind of horsepower would it turn? The Maico engineers felt 65 to 70 horsepower at the rear wheel was not out of the ballpark. A small drawback is encountered, though, if the 760 is allowed to breathe fully. It’ll shear conventional frame tubes in a rather short time. When the engine is allowed to spin to its max, the vibration level becomes unmanageable. No gearbox will tolerate that load for long, and the conventional Maico primary chain drive becomes grossly over-stressed. The stock Maico clutch will turn into a stack of Doritos under 70 ponies. Thus, the deliberate detuning is not only desirable, but necessary.When one considers that a normal 490 Maico can handle a solid 50 horsepower to the rear wheel for a season, with no hassle, then the rather mild 43 horses on the 760 will seem well within sensible boundariesTHINGS PECULIAR TO THE BEAST

That small (!) piston is from a 490 Maico. The Big One is a 760 slug.

With the stock 2.5-gallon motocross tank in place, the 760 only managed 15 miles before it was sucking wind through the float bowl. Of course, our race test was conducted under some pretty gruesome circumstances: the Blackwater 100. Here, the deep mud had us spinning the rear wheel a great deal. Under normal conditions, 25 to 28 miles can be squeezed out of the stock gas tank. Six Days riders all used larger tanks but still could not manage 50-miles range. Fortunately, gas areas are plentiful at a Six Days.

Can you guess which head is from the 760 and which one is from a 501?

Oddly enough, the 760 could not be kickstarted when cold. It had to be push-started. Then, after the bike was warmed up, it could be fired as easily as a well-tuned 250. No amount of choking or priming would let the 760 get lit when cold, though. While the big bike could be booted through without using the compression release, it was not the hot ticket. One bite back and the kickstarter could be instantly sheared off. Without using the compression release, a 150-pound man could literally stand on the lever and it wouldn’t move through its arc.Obviously, lots of gas is wasted as it passes through the combustion chamber. Maybe that’s just nature’s way of telling us that perhaps a 760 single doesn’t make much sense. It was necessary to jet the huge engine on the rich side, just short of blubbering, to get sufficient fuel, and there was still some detonation and pinging under heavy loads. Maico assured us that the detonation would not hurt the engine — that it was just a characteristic quirk of the bike.TECHNICAL TRIVIAThe 760 runs a normal 490 rod and crank and uses a 250 gearbox to transfe

r the power. A standard clutch is also used. It held up well for us, with no slippage at all. This speaks highly of the basic Maico drive train.

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Trivia stuff: bottom end is from a Maico 250; all other components, including suspension goodies, are straight from a 490.

Our test machine used a standard 1981 Mega 2 chassis, with no enduro or ISDT hardware attached. This gave us a bike that weighed just about 10 pounds more than a stock 490. Not bad. After putting in some time on the bike, we started referring to it as "the two-stroke that feels like a four-stroke."The piston measures a mammoth 107.52mm across and is derived from a Porsche industrial engine, then highly modified. The piston skirts are deeply cut and the slug itself is rather light for something that big. No doubt the lightness also helps to keep the vibration down. A single dykes ring does all the sealing.Ring end gap and piston clearance are critical on the 760, because expansion must be considered. A careful setup will yield a reliable engine, while one set up a fraction too tightly will wear out rapidly. A loose engine will invariably crack skirts and get terrible mileage and performance. Clearly, the 760 is not for Joe Lunch-box.CAN I GET ONE?No. So don’t ask your friendly local dealer. In fact, there are only three of the 760s in existence. We were pleased to be able to get our hands on one. This year (1981), there will be no more over-750cc classes in the ISDE, so the Maico monsters will be relegated to the factory museum.The factory has no plans to market any version of the 760. They’re candid enough to admit that the 400 or 490 can do anything that the 760 could, with less attendant hassle. In retrospect, the 760 was simply made to prove a point and to garner some Gold Medals in Six Days Competition, to keep Maico in the limelight.Well, they did all that and a little bit more. They made some history. The largest two-stroke single in the history of motorcycles was not only built, but run, successfully in world competition. They had fun, proved a point and left their mark.It was an honor and a genuine thrill to take the last ride on that warhorse before it was put out to pasture. SPECIFICATIONS - MAICO MEGA 760
ENGINE TYPE: Two-stroke, piston port, air-cooled, single
BORE AND STROKE: 107.52mm X 83mm
DISPLACEMENT: 752.0cc
HORSEPOWER: 43.78 at 4000 rpm
CARBURETION: 40mm Bing, tvpe V54
RECOMMENDED GASOLINE: Premium 92 + octane
FUEL TANK CAPACITY: 9.51 liters (2.5 gallons)
FUEL TANK MATERIAL: Plastic
RECOMMENDED OIL: Bel-RayMC-3; Bel-RayMC-1
OIL CAPACITY: N/A
AIR FILTRATION: Oiled foam in still airbox
CLUTCH TYPE: Wet, all metal, multi-plate
TRANSMISSION: Five-speed
GEARBOX RATIOS:
1 … 2.98:1
2 … 2.17:1
3 … 1.65:1
4 … 1.25:1
5 … 1.00:1
GEARING. FRONT/REAR: 15/48
IGNITION: Pointless electronic Bosch external rotor
PRIMARYKICKSYSTEM? Yes
RECOMMENDED SPARK PLUG: Champion N2 or N84G or NGK B9ES
SILENCER/SPARK ARRESTER/QUALITY: silencer only/ fairly quiet
EXHAUST SYSTEM: High-pipe, right side
FRAME, TYPE: Double downtube, full cradle, chromoly tubing
WHEELBASE: 1492-1528mm (58.7-60.0 inches)
GROUND CLEARANCE: 345mm (13.58 inches)
SEAT HEIGHT: 960mm (37.8 inches)
STEERING HEAD ANGLE /RAKE: 28.4 degrees
TRAIL: 126mm (4.96 inches)
WEIGHT WITH ONE GALLON GAS: 249 pounds
WEIGHT, DRY: 238 pounds
RIM MATERIAL: Aluminum alloy
TIRE SIZE AND TYPE:
FRONT: 3.00 x 21 Metzeler two-ply nylon
REAR: 4.50 x 18 Metzeler two-ply nylon
SUSPENSION, TYPE AND TRAVEL:
FRONT: Maico telescopics, 42mm tube – 310mm (12.2 inches)
REAR: Swingarm with dual Corte & Cosso shocks – 310mm (12.2 inches)
INTENDED USE: Experimental/Six Days Competition
COUNTRY OF ORIGIN: Germany
RETAIL PRICE, APPROX: Not Available/Only three in existence
PARTS PRICES/HIGH WEAR ITEMS:
PISTON ASSEMBLY, COMPLETE: Don’t ask
RINGS ONLY: Don’t ask
CYLINDER: Don’t ask
SHIFT LEVER: $20.20
BRAKE PEDAL: 24.80
FRONT SPROCKET: 13.20

PHOTO CAPTIONS(maico1, 4.c photo) The author spent considerable time extracting the big 760 from deep mud in the Blackwater 100 race.(maico2) Massive fins were actually almost two inches wider on each side than the old 501 barrel which the top end is based on. Weight difference between the two engines? The 760 was only nine pounds heavier.(maico3) Maico East folks delivered the 760 for the race and hung around to help with pit stops after dialing the bike in. That’s Gary Herto with the cowboy hat.(maico4) Pipe barely clears the huge head. Horsepower was rated at only 43 at the rear wheel, but the 760 pumped at 26 ponies at only 1200 rpm! That’s barely above idle.(maico5) The 760 required only a blip of the throttle to blast out of deep sand turns. The author demonstrates at the old Indian Dunes track.(maico6) That small (!) piston is from a 490 Macio. The Big One is a 760 slug.(maico7) Can you guess which head is from the 760 and which one is from a 501?(maico7) Trivia stuff: bottom end is from a Maico 250; all other components, including suspension goodies, are straight from a 490.