The Yamaha XS1100

Fashionably late for the Superbike ball

| January/February 2010

Yamaha XS1100
Years produced:
Claimed power: 95hp @ 8,000rpm
Top speed: 136mph (period test)
Engine type: 1,101cc air-cooled, DOHC inline four
Weight: (wet) 602lb (274kg)
MPG: 30-40
Price then: $2,989 (1978)
Price now: $1,500-$4,000

When the time came for Yamaha to join the Superbike ball, the Yamaha XS1100 (also known as the Yamaha XS Eleven) was fashionably late. Liter bikes from Honda, Kawasaki and Suzuki were already at the dance and making a name for themselves. Although the competing entries filled different needs, each was powered by an engine displacing 1,000cc or more.

Honda had broken the 1,000cc barrier with the Honda GL1000 in 1975. It was followed by the Kawasaki KZ1000 in 1977, and then the Suzuki GS1000 in 1978. Until 1977, Yamaha’s biggest model was the Yamaha XS650 twin. The triple-lung Yamaha XS750 rolled into view for 1976, but left much to be desired when it came to a highway touring motorcycle and was a bit of a slug when you rolled on the throttle.

Not just bigger, better

Knowing they needed a bigger partner to compete in the hoedown, Yamaha turned up the wick and introduced its XS1100 for 1978. Much of the media had expected a 1,000cc machine to fill the spot, but the designers at Yamaha threw an unexpected performer onto the dance floor. Not only did the latest XS carry more cubic centimeters than the others, but it also featured a 4-cylinder engine, a first for the tuning-fork firm. With Yamaha’s sights set on the long haul rider, the big XS was armed for bear.

On the surface, the XS1100 seemed pretty straight forward, but like a lady behind a feathered mask it hid a few surprises. When the engineers were drawing up the 1,101.6cc engine, they did far more than simply tack an extra lung to the existing 3-cylinder engine from the XS750. While being fairly typical in its layout, Yamaha threw in some technological features to enhance power. Dual overhead cams were expected, but the four 34mm Mikuni constant velocity carbs — a first for an inline four — weren’t. The XS also benefited from very unique combustion chambers.

While hemispherical combustion chambers, with intake and exhaust valves placed across from each other and a centrally located sparkplug (hence the term “hemi head”), were the performance norm, they had inherent limitations. Chief among them was upping compression ratio without resorting to pistons with huge crowns, increasing weight and slowing heat dissipation. To get around this, Yamaha developed a complex “polyspheric” combustion chamber, a design that required six machining operations to achieve. The multitude of cuts and shapes milled into each combustion chamber produced the same volumetric efficiency of a hemi but without any of a hemi’s drawbacks, allowing Yamaha to use slightly crowned and lighter weight pistons (211 grams).

12/22/2015 10:37:31 PM

Heavy. Not a canyon carver, but great, if you have lots of pavement. I have a silver full bagger 1980 (built June '79) and a black/gold '79 Special. Building brakes on the Special; the '80 starts by just thinking about touching the starter button; braided hoses are on the way. I call it "Kong."

3/26/2015 5:38:59 PM

Gorgeous example there Doug. Best colour as you say, and a real torque monster. I remember the bike well, as a pal over here in Ireland owned the very first one brought into my country !! It was a silver example. Some great detail there too in the piece, very good stuff. believe it or not, I still own the original test on this bike from Motorcyclist magazine, article written by Ken Vreeke I think his name was, and they rode the bike from LA to NY in about 36 hrs if memory recalls. great stuff. If memory serves right, it quartered in 11.83 secs at 115.38 mph. Going purely on memory here from 1978 !!! I must dig out the mag from my extensive files !!!! Damn impressive stuff from a 600 lbs plus fully fuelled bike. I currently own a natural successor to that bike, a 1986 Yamaha FJ1200 , and its a powerhouse indeed. I brought that bike back from Boston where I lived up until 2011. Best regards Dave

3/24/2015 12:03:28 PM

I have a "barn find" bike I bought last year. It was originally sold in Anaheim California in the fall of 1978. It was only used 318 miles and had been stored ever since until it was purchased last year. The last sticker on the license plate is from 1981, and I have the registration documents for those 3 years (1978-1981) Luckily the bike was stored in an environment that didn't damage anything. All the mechanical components were like new. The original tires still appeared to be in good shape although they were hard to the touch. Unfortunately they do not make "standard dimension" tires any longer so I replaced them with modern tires of the original brand name but did keep the old ones too. The carburetors were professionally cleaned and reconditioned, the oil in the engine and drive train was replaced and now the bike starts and runs like a brand new motorcycle. Below is a link to some pictures I just took over the weekend. Since I bought the motorcycle I rode it approximately 80 miles, which were mostly test drives at various stages of the "awakening" of the mighty XS11. Here is the link:

Ride 'Em, Don't Hide 'Em Getaway

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