4-Stroke Fun: 1977-1982 Yamaha XS400

Comparing the Yamaha XS400 with its primary rivals, the Suzuki GS400 and Kawasaki KZ400.


| November/December 2017


Yamaha XS400
Years produced: 1977-1982
Power: 32-36hp @ 8,500rpm
Top speed: 96mph (period test)
Engine: 391cc air cooled, SOHC parallel twin
Transmission: 6-speed, chain final drive
Weight/ MPG: 391lb (wet)/53-58mpg
Price then/now: $1,348 (1977)/$600-$2,000

Until the early 1970s, with the exception of Honda, mid-size Japanese motorcycles were always 2-strokes. But with the pending demise of 2-stroke street bikes in the U.S. market looming, the other three big Japanese bike builders had little choice but to look to the Otto Cycle for their future — even though they continued to make 2-stroke street bikes until the end of the decade.

Kawasaki was the first to offer a sub-500cc 4-stroke with the KZ400 twin in 1974. Yamaha followed in 1976 with the XS360, and Suzuki introduced the GS400 in 1977. Launched in the U.S. in 1977, the XS400D was essentially a bored-out XS360 (66mm bore for the 360, 69mm for the 400). As such, it was an air-cooled 4-stroke parallel twin with two valves per cylinder and a 180-degree crankshaft of 52.4mm stroke. Drive to the single overhead camshaft was by chain with an automatic tensioner. The crankshaft ran on three split-shell plain main bearings, with plain bearings also used for the big ends. A pair of 34mm Mikuni CV carburetors fed the iron-sleeved cylinders. Starting was electric, with a kickstarter fitted as backup. Drive to the 6-speed transmission was via a straight-cut gear primary and wet multiplate clutch. Unlike its competition, the XS had no balancer shaft. 

The unit construction power unit fitted into a mild steel tubular frame with a single downtube and dual cradle below and behind the engine. A non-adjustable telescopic fork controlled the front wheel, while a swingarm and 5-way adjustable shocks were fitted at the rear. Both front and rear wheels were cast alloy with a single disc brake. The XS400 was especially anticipated, because its 2-stroke sibling had been the fastest of the 400s to that point. Much of the XS400D’s styling was influenced by the RD400, with which it appeared to share some components. Though listed as a “commuter” model, the XS400D came equipped with full instrumentation and self-cancelling turn signals.



The squared-off gas tank and seat on the XS400D gave it classic lines, but for 1978 a restyled teardrop gas tank and slightly stepped seat were fitted on the XS400F, “Capturing the essence of the ‘American Triumph’ look,” Cycle Guide said. Also available in 1978 was the XS400-2, a spoke-wheel, drum-brake, kickstart-only model missing self-cancelling signals and with a lower MSRP. A further redesign for 1980 gave the cruiser-like XS400SG a deeper step to the seat, pull-back bars, shorty mufflers and a drum brake replacing the rear disc. The XS400 was replaced in 1982 by an all-new double overhead cam, counter-balanced twin, the Seca 400. 

So was the XS a worthy successor, or a different animal altogether? A Cycle World tester called the XS400 “the roughest running 400 4-stroke twin on the market,” with vibration making the mirrors useless at speed. Cycle was a little kinder, noting the little twin “pulls evenly and willingly to and past redline, and during short bursts, the vibration is not annoying. But if you jump on the highway … you may find it disappointingly buzzy.”

baronbe58
11/16/2017 8:35:37 AM

Won the 400cc class of the 1983 24 Hours of Nelson Ledges on a Yamaha XS400. Classic tortoise and hare race. The XS400 would go 2 hours between fuel stops. So even though we changed riders each hour, every other stop was a quick rider only. We out lasted a field of 350 and 400 two strokes. Fun times and good memories. Riders: Rocky Dean Gary Maslanka Martin Morrison Jeff Poulten Dave Williams


baronbe58
11/16/2017 8:35:24 AM

Won the 400cc class of the 1983 24 Hours of Nelson Ledges on a Yamaha XS400. Classic tortoise and hare race. The XS400 would go 2 hours between fuel stops. So even though we changed riders each hour, every other stop was a quick rider only. We out lasted a field of 350 and 400 two strokes. Fun times and good memories. Riders: Rocky Dean Gary Maslanka Martin Morrison Jeff Poulton Dave Williams


baronbe58
11/16/2017 8:17:59 AM

Won the 400cc class of the 1983 24 Hours of Nelson Ledges on a Yamaha XS400. Classic tortoise and hare race. The XS400 would go 2 hours between fuel stops. So even though we changed riders each hour, every other stop was a quick rider only. We out lasted a field of 350 and 400 two strokes. Fun times and good memories. Riders: Rocky Dean Gary Maslanka Martin Morrison Jeff Poulten Dave Williams








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