One night last week, while lane-splitting through traffic on my way home from the office, I caught a whiff of something that brought back a lifetime of memories for me. It was the smell of burning Castrol R, an oil that was popular in racebikes for many years. Castrol R is made from castor beans, and it turned out I was smelling the exhaust from a Mercedes Benz that had been converted to run on vegetable oil-as claimed on a large sticker in the rear window. Our olfactory systems have long been linked to emotion and motivation as well as memories, and for me the smell of Castrol R has always been tied to two-stroke racebikes.
There were plenty of oil-burners-two-stroke and four-stroke-racing at Harewood Acres and Mosport, the two tracks I went to as a pre-schooler with my father and brothers, and even then I was well familiar with the very pronounced and distinctive smell of Castrol R. It's a difficult scent to describe-not pungent or sharp, but rather smooth and almost sweet. For a two-stroke junkie, the Castrol R scent is as powerful as the smell of mom's homemade apple pie fresh out of the oven. When my brother started racing an early-'70s TZ250, of course it ran on R. Even Castrol recognizes the impact the smell of its product has had in the industry: "The smell of Castrol R epitomized Castrol's presence in motorsport for many," reads the company's press material. I was cutting neighborhood lawns in those early days, and I'd always sneak some of the leftover pre-mix race gas to run in the push mower. I don't know if the mower ran better or if it was the smell that urged me to work faster, but for some reason the lawn cutting went a lot quicker when R was in the tank. The extra smoke took some explaining, though.
Sweet smells and happy memories aside, about the same time I was sniffing the castor oil and reliving my two-stroke past, Honda announced that it will be discontinuing its line of two-stroke motocross bikes after '07. To me, that is sad news, because it's yet another sign that the return of two-stroke streetbikes is getting even farther away, not closer.
As you most likely know, emissions concerns were responsible for killing off two-stroke streetbikes years ago, and four-stroke engines have been steadily infiltrating other powersports and utility industries ever since. As bleak as things seemed from the oil-burner side of the fence, for a while it looked like the two-stroke might be making a comeback in many niches of the motorsports market over the last few years. For the average dirt rider, rebuilding a cam-and-valve top-end every 25 hours of operation can be a big and expensive operation, but freshening up a two-stroke is fairly straightforward and relatively cheap. Four-stroke motocross bikes are also coming under increasing fire for noise issues: With aftermarket pipes, the sound is more obnoxious and carries farther than a two-stroke's softer exhaust note. Two-strokes are still popular for play riding, and all the major manufacturers-including Honda, until now-have been regularly updating their two-stroke dirt models.
Aprilia has marketed direct-injection scooters for several years, and similar technology is crossing over into the marine and snowmobile sectors. The Italian manufacturer's 50cc Scarabeo has a fuel consumption of more than 100 mpg, an important figure with today's gas prices. Several companies, including Yamaha, offer direct-injection two-stroke outboard engines that are powerful, light, economical and very environmentally friendly. And Ski-Doo has a full line of two-stroke snowmobiles that meet EPA standards. Every so often there's a ray of hope for a two-stroke streetbike, like Dr. Rob Tuluie's Tularis racebike that utilizes a twin-cylinder Polaris snowmobile engine. Or the EXP-2, a prototype clean-burning two-stroke dirtbike built by Honda in the mid-'90s.
Unfortunately, as time goes on I think it's becoming less likely we'll see a two-stroke streetbike again. One hurdle is still emissions regulations, which are getting tougher and tougher every few years. Just as the technology catches up and a two-stroke engine seems an economically viable option for a sportbike, the standards become tighter, forcing even more development just to meet that iteration of the regulations. Why invest in an engine design that could be useless in five or even 10 years?
The biggest drawback I see is that four-stroke sportbikes are just getting too good. The potential performance benefit that a two-stroke could offer is decreasing every year, as the big manufacturers concentrate development on four-strokes and private companies and die-hards are left to carry the two-stroke banner. And as MotoGP and motocross transition from two-stroke to four-stroke, the scales will only shift farther in that direction.
I still peek at the classifieds every once in a while and dream of another TZ250, RZ350 or RS125, but maybe what I should be doing is looking at one of those Mercedes that runs on veggie oil. At least that way I can be sure of having that Castrol R smell around to remember my old two-strokes by.