The Motorbike Archives

And you're carving, out there on Sunset, precisely, playing Calvin Rayborn loose among the radishes, red jacket, red helmet, a fire-engine-red motorcycle, hands down low, feet up high, knees working on the gas tank, notching a succession of perfect shifts, steering the motorcycle rather than merely leaning it over, tinkering with the precision that the motorcycle demands and responds to, fooling with the enormous torque that Paul Dunstall has given an already torquey engine, trailing behind you the most beautiful, rich, deep, smooth exhaust note this side of Milwaukee, listening to the hiss of the centerstand as it kisses the pavement going around right-handers, feeling solid resistance as the sidestand grounds on turns to the left. Dunstall's 810 Norton Sprint: this is where it belongs, this is where it belongs: out where other people can see it.

For a hot-rod (American terminology, or close enough, for England's Cafe Racer), the mighty 810 is surprising in its restraint. One gets the impression that, had he wanted to do so, Dunstall could have built the 810 to be quite a bit faster. But then it would have lost reliability, it would have become hard to start (which it isn't), it would have been a handful to ride, and it would have been lots noisier. As it is, it is well-integrated for a semi-custom, conservative mechanically, and not as punishing as you would expect.

But you can't buy one. Not complete, not in this country. You could go to England, have Paul do one up to your specifications, and bring it back with you under the Personal Export provisions. Or you could buy all the parts from Dunstall and do one up yourself.

Here's how Paul goes about it. He buys a complete Norton Commando, strips off all the standard parts that he plans to replace, and sells them back to Norton-Villiers: parts like the gas tank, seat, handlebars, sliders, cylinder assembly, pistons, front brake, exhaust system, valves, cam followers, foot controls, and front fender. He then installs 1/8" larger intake valves, his own guides and springs, reshapes the combustion chamber to accommodate a cylinder assembly with 3mm more bore and about 10 pounds less weight, decreases the intake valve angle from 28 degrees to 261/2 degrees from the vertical, polishes and re-contours the ports, hogs out the intake manifolds, sticks in his own lightweight cam-followers, and adds a high-pressure oil feed to the rocker assemblies; the engine uses, of course, Paul's own lightweight 10-1 cast pistons (the crank assembly doesn't have to be rebalanced), and a pair of 32mm Amal Concentric carburetors. Which just about does it for the engine.

The tank and seat, both beautifully rendered in color-impregnated fiberglass, replace the stock Norton items. The seat is secured only by a pair of tabs which a pair of large knurled aluminum hand knobs attach to the upper shock mounts, and an additional tab which rests on the frame loop used on the stocker to support the rear fender and the taillight assembly. The tank is held by rubber-doughnut-bushed bolts in front and a rubber band looping under the backbone tube behind.

Semi-clip-ons are used instead of standard handlebars, the front fender is Dunstall's own lightweight fiberglass item, and the slick dual disc front brakes come from Dun-stall as well.

Farther back, aluminum mounting plates locate the rear-set brake and shift mechanisms—plates which are less attractive but more competition-looking than the stock polished Norton forgings. The plates also support (in rubber bushings) Dr. Gordon Blair's patented two-into-one-back-into-two exhaust system, one of the bike's more pleasing aspects.

What's left? Norton's fabled Commando frame, Roadholder forks, the engine's short-block, Norton-Girling rear shock absorbers with slightly heavier springs, and the stock rear brake assembly, reduced in effectiveness by a variation in leverage at the foot pedal.

The bike takes a lot of getting used to. An historic imprecision in low-speed metering accuracy by the Amal carburetors means, simply, that the bike stalls a lot before you get used to it. But the bike starts easily, even if it is rough to kick over—that is, it starts easily if you know what you're doing: just the right amount of throttle, and just the right amount of choke. (The choke lever is mounted on a stub of capped handlebar tubing clamped in the stock handlebar position on the top triple-clamp. A good way to use the handlebar bosses, but a bit heavier than necessary.) The right footpeg has to be folded up before you can try to start the engine; and when it's finally running, you have to be careful returning the kickstarter lever to its normal position. If you aren't, your toe will contact the underside of the shift lever, and before you know it, the transmission has been bumped into first and you've stalled again. Don't worry about it; the first time it happens, you'll be so damned mad that it'll never happen again.

Once underway, you can't help feeling like a gen-you-wine roadracer. It's a neat feeling, within limits. The bike, face it, is a bit of a handful in town, what with its reluctance to idle and the fact that the seat gets you pretty high up in the air, which makes footing around difficult for a six-footer and nearly impossible for somebody five-feet-eight. Additionally, the seat offers minimal padding, and what padding it does have tends to slide around under its covering and ultimately migrate towards the rear, where the passenger sits (who has an enormous amount of room, but nothing except the operator to hang onto).

But what makes the 810 most awkward in the city is the seating position. The footpegs are a solid 6-8 inches behind their stock location, and the handlebars are lower, farther to the front, and closer together than on a production Commando. So you support most of your upper-body weight on your hands, which becomes tiring, unless you call into play a bunch of little muscles in your back and pelvis, which is even more tiring.

The punishment meted out to your hands and forearms is worsened by the character of the Dunstall handgrips. They are relatively small in diameter, faintly barrel-shaped, and tightly patterned. Without gloves, after a hundred miles or so they begin to feel like wood rasps. With gloves, you're simply left with a pair of very stiff wrists. Stiff, and tired, because the clutch is rather heavy, and the throttle springs are remarkably stout, which an extremely slow throttle does little to alleviate.

Around town, the engine makes up for as much of it as it can. The 810 is a revelation. Bob Trigg's Isolastics have seen to all of the engine vibration. (To find out how much there is, simply prop your foot up on the chaincase at about 35 mph and keep it there. If you can.) Once the carburetors come off idle, metering is accurate enough, and the Dunstall chuffs along quiet, smooth, and sedate as a BMW. Blair's exhaust system for the 810 is a marvel. Two short header pipes converge just in front of the forward engine mount, a single larger tube carries the exhaust below the engine, and it splits back into two mufflers right under the transmission. The mufflers themselves are quite simple; a perforated disc is located up front, perforated tubing lined with fiberglass along the muffler's main body, and a nest of seven

short, small-diameter lengths of tubing at the big end. According to Dunstall, the system is worth five mph in the quarter and five mph on top. It may well be. But performance improvements aside, the pipes are worth their weight in gold in terms of exhaust note and solid noise reduction. In Cycle's decibel test, the 810 registered 88.9 dB(A), or about two decibels more than the two 100cc street machines tested in the March issue, and four decibels less than the Suzuki 380 tested in the same issue. At last! A high-performance exhaust system that honest-to-God muffles!

Enough of city traffic—the 810 can tolerate it, but barely. The bike is noticeably more relaxed romping through mountain roads, banked turns, switchbacks, long straightaways with tight corners at the end where it can show off its superb front brakes. Both nine-inch discs are rigidly mounted—they don't float. Neither do the calipers. But they don't have to, since each caliper assembly has two live pucks. (Which makes Dunstall's installation different from the single disc found on the front of the Honda Fours and the 450 and on the Kawasaki 750 and 500. On the Japanese bikes, the caliper assembly has to pivot, since only one live puck is used.) Both caliper slave cylinders are governed by a single master cylinder with two brake lines. One runs directly to the right caliper; the other incorporates a pressure switch (similar to that on the Hondas) that controls the stop light. Lever pressure is lighter than any of the Hondas or the Kawasakis (or, for that matter, either of the two new Norton Commandos), and braking force was judged to be superior to all. The front tire, a massive 4.10-19 Dunlop Roadmaster K81, is a necessity. The brake demands it. But the tire imposes a penalty of its own: while the 810 steers accurately, it cannot be flicked left-right-left in the manner of some of the more nimble middleweights.►