Some motorcycles evoke a certain thought at first sight. When I first saw this small, Yamaha-powered dragster in the window of the Tea Room, all I could think of was how up to date my health insurance coverage was. The fact that someone was crazy enough to even want to build this recumbent-bicycle-looking thing based on a Yamaha two-stroke says a lot about the mindset among aficionados of these cam-less wonders.
James Meridieth of Gallatin gave me the details on the little yellow dragster: It was built in Knoxville in the early '80s by Glen Phelps and Terry Johnson of Motorcycle Specialists. The frame came from California (land of crazy two-stroke freaks, even in the '80s) and is fitted with a Yamaha R5 350 bottom end, a road-race TR3 top end, and bulbous stinger expansion chambers. The YZ80-sourced brake is tiny, and there's a four-inch slick on the back. "It originally belonged to Loyd Graham," he says. "I asked him to sell it to me for over 25 years before he relented and let me purchase it."
It was built to run at 411 Dragway, but it's never been used on a race track. James has cranked it up and ridden up and down the driveway, but it's not even close to being street legal, a trapped mosquito ring-ding-dinging to be free. James has since moved it to Tommy's Motorsports in Clinton, so maybe now that it's out of the county someone will want to fire it up and launch it down Highway 61. Or James could take it to a large parking lot and tell security it's a ½ scale radio-controlled model.
Except for weed-whacker-sized mopeds, and plodding Eastern Bloc commuter bikes like old MZs, two-strokes are all about the power band. Every time the piston comes up, there's an explosion. A two-cycle engine generates double the bangs at a given rpm compared to a four-cycle motor with the same number of cylinders, doubling your pleasure and your fun (and halving your gas mileage). Every rider should own a nice-running two-stroke motorcycle at least once, just to understand the addictive feeling of the front wheel floating across the pavement as the motor comes on the pipe, and to savor that "Bbrrrriiiinnggggg" sound.
Unfortunately for the environment, this wonderfully simple technology relies on stinky explosions, caused by the mixing of burnt and un-burnt fuel and lubricating oil in the combustion chamber. Try to tune a two-stroke to make those explosions cleaner, and you get even more power, right before the hotter combustion and pre-ignition punches a hole in a piston, or distorts it to the point of seizure. And without the dedicated lubrication system of a four-stroke, they tend to wear out faster. But that's just part of the fun of being a stinkwheel owner.
Due to emissions regulations and a desire for racing tech to be useful in production applications, racing two-strokes are going the way of tube-type tires and WebCrawler. Even in European road racing, where stinkers were the dominant technology since the '70s, November 3, 2001 marked the last 500GP (later MotoGP) race won by a two-stroke motorcycle, when Valentino Rossi won the final race of the season at Jacarepagua, Brazil aboard the Nastro Azzurro Honda NSR500. By 2003 the fearsome two-strokes were gone from the premier class, replaced by 990 and then 800cc four-strokes. The 250GP support class runs two-strokes through 2010, after which a new four-stroke 600 series will replace them as well.
Likewise in U.S. motocross, where two-strokes were the only paradigm from the late '60s through 2003-2004 or so. In 2004 James Stewart won the last 125 national on a two-stroke, and the year before Ricky Carmichael took the last two-stroke-powered 250 National win. The new four-stroke motocross bikes may run cleaner, but the high piston speeds required to make competitive power wear out top ends almost as fast as their two-stroke predecessors, with more parts and complexity required for a rebuild.
In vintage racing, however, two-strokes will live on, their simplicity and light weight keeping them competitive against their four-stroke contemporaries.
Two-strokers are an obstinate group, however, and often revel in the black arts of expansion-chamber dimensions, port maps, and the trueing of roller-bearing crankshafts with little lead mallets. They really enjoy their machines, while at the same time have often been on the greasy-wrench end of seized pistons or torched crank bearings, producing a slightly crazed love-hate look in their eyes. And if you needed further proof that two-stroke motorcycles are rapidly becoming anachronistic relics, Knoxville's own 555 plan their 2010 dumb-ass adventure on old two-stroke enduro bikes. Could a 2012 drag-bike challenge be next?
Fred Sahms is a curmudgeonly Luddite who has been soiling his fingernails with old motorcycles for 25-plus years. His garage is located somewhere in North Knoxville. Drop him a line at fred(at)fredsgarage(dot)net.