Retrospective: Yamaha SRX600S (SRX-6): 1986

photography by Dave Martens

[This Retrospective: Yamaha SRX600S (SRX-6): 1986 was originally published in the June 2011 issue of Rider magazine]

It was a bad time to introduce a new motorcycle in the United States, with the economy in recession and new-bike sales falling drastically. But it was a great notion, as there is something about big singles that stirs passion in many riders. Few of us are old enough to remember the British street thumpers of fame—and occasional infamy—like the BSA Gold Star, the Norton International, the Velocette Thruxton, those rorty one-lungers whose exhaust note alone could raise the hairs on the back of any rider’s neck.

The Thruxton was the last sporty single to go, laid to rest in 1971, and 15 years later Yamaha came up with the SRX-6—a 595cc oversquare single with a bore of 95mm, stroke, 84mm. Spinning at 6,500 rpm, the engine was rated at 40-plus crankshaft ponies by the factory, while a dyno at the rear wheel measured only 33. Reality occasionally intrudes, but a good rider on a twisty road could keep up with more powerful machines. One thing this engine had which the Brits never developed was a counterbalancer, to keep the vibrations under control, this one gear-driven off the crank. If the boys at the Hall Green works in Birmingham, where Veloce, Ltd. was based, had figured that one out in the ‘60s the company might still exist. Doubtful but possible.

In many ways this SRX600 was a follow-up to the well-received SR500, the 500cc street single that Yamaha sold from 1978 to 1982. The SR was an entertaining machine, more utilitarian than sporty in nature, its only drawback being that pesky kickstarter, as American riders were getting lazy and wanting only to push a button. It did sell in sufficient quantities to keep the bean-counters happy for five years, no mean feat, and then reappeared four years later with an extra 100cc and an X added to the alpha-numerology. Interestingly, this SRX was intended for the Japanese home (as a 400) and European (with 608cc) markets, and only imported here as an afterthought, with a 595cc engine that had already passed DOT requirements in the XT600 version.

With the initial announcement that the SRX was coming stateside, a rumor arose that the U.S. model would be fitted with an electric starter. Not so. Nobody from Yamaha ever claimed credit for having championed the SRX for the United States.

Despite the old-fashioned kickstart, this was technically a pretty refined unit. The cylinder head, a rather sophisticated casting, had four valves operated by a single overhead camshaft, which was in turn chain-driven from the crankshaft. It had two 37mm carbs, one being slide-operated and essential in the first half of throttle, the second a constant-velocity unit that kept the combustion chamber full at higher revs. The fuel fed in to the chamber was compressed 8.5 times, ignited via a CDI ignition and a single spark plug, with two header pipes taking the spent gases out through a large, overly quiet muffler. The exhaust system was such a complex affair that a rider who wanted slightly more than a soft burble could not easily fit an aftermarket muffler.

Two un-Japanese aspects of the engine were, first, the remote oil tank, a beautifully finned piece housing 2.5 quarts and sitting under the carbs, and second, the screw-and-locknut valve-lash adjusters. Bless the engineers for sim­plifying the home-mechanic’s life.

Gears ran the power back through a wet clutch to a five-speed transmission, with a 520 chain putting the power from a 15-tooth output sprocket to the rear wheel’s 37-tooth. Torque, claimed at the crankshaft, was 34 lb-ft at 5,500 rpm, with 28 or so reaching the back wheel, so this was an engine that needed revs. Part of that was due to the light flywheel, at least light in comparison to the old Brit bikes, meaning that the rider was going to be shifting a lot to keep the revs up between 4,000 and 6,000. Redline was seven grand, but not much boost was found in that last thousand.

The chassis was a thing of modernistic beauty, with the frame a box-section double cradle that provided stiffness and helped the good handling. Should the engine ever need to be worked on, a section on the right side unbolted for ease of removal. The 36mm KYB fork offered more than 5 inches of wheel travel, had a center axle and was angled at a modest 26 degrees, with 4.1 inches of trail. At the back was a box-section swingarm, and in a sort of retro-fashion, a pair of Yamaha’s shock absorbers with remote reservoirs, preload adjustability and 4 inches of wheel travel. This arrangement allowed space for that big muffler.

The cast wheels were both 18 inches in diameter, sporting skinny Bridgestone Exedras, a 100/80 on the front, 120/80 at the back. Stopping was done by squeezing a pair of 10.5-inch discs forward, a single 9.5 aft. This added up to a modest wheelbase of 54.5 inches, and when the tank was filled with 3.9 gallons of gas the curb weight was just under 390 pounds.

Hop aboard; the 30-inch seat height was not intimidating. Choke on, fold up the right-side footpeg, swing out the kickstarter 90 degrees. No compression release on the bars, as all this was being done automatically, but it was wise to bring the piston to just past top dead center. Straddling the bike, the kicker’s left foot is on its peg, the right on the top of the starter, the hands on the bar grips. Closed throttle, pray, plunge downward. There is always trickery involved in this refined art form, as well as unanswerable questions. But the SRX was a lot better than the old Thruxton.

Settle into the saddle, watch the little tach rev—in its own vibratory way the engine told the rider when to shift. Keep the revs between four and six grand, stir the tranny, and good times were to be had. Not crossing the Great Plains, perhaps, on long, straight roads, but on the backroads of the eastern states, in the Ozarks, and winding around the many mountains out on the West Coast. This was a day-ride bike, maybe a weekender with a bit of luggage on the pillion saddle.

And fun! At $2,600 the SRX was not cheap, and one could buy a four-cylinder Yamaha Radian 600 for less money, but you couldn’t get that visceral pleasure of a thumper. This was a special bike for special riders—of whom there were not enough. The SRX disappeared after only one year, with great discounts on the unsold models.