The Motorbike Archives

DG racers are the hot-tip in mini-motocross. The Anaheim company campaigned RM80 Suzukis in 1977, though DG can put you on a similarly outfitted YZ80 Yamaha. DG RM8Os proved to be tough, durable little units all year. Are replicas expensive? Of course. You send DG 18 crisp one-hundred dollar bills, and you get back a crate and loose pocket jingle in return. And more. The first time the customer runs his DG racer moto-crosser, Harry Klemm, DG's research and development whiz, or Ted Boyko, DG's head wrench for the mini-motocrosser race team, will be trackside to see that the bike runs right. And that's anywhere in the continental United States.

Ken Boyko likes to match machinery to the rider. Maybe the little voice on the other end shouldn't have a tapped-to-the-max bike, lest he forever sing like a choir boy. Boyko interrogates the father: How much does his son weigh? How much experience does he have? What do they know about maintenance? How fast is the kid? Boyko listens carefully, knowing how enthusiasm for the future can brighten the lap times of the past. "Never talked to a parent whose kid wasn't just a jet," Boyko allows.

The DG bikes are state-of-the-art, and here's what money can buy for the NMA (National Minicycle Association) Eighty-Modified Class.

Stock RM80 suspension is not compatible with a 14.5 horsepower engine, and the speeds it can generate. A Betor fork replaces the standard Suzuki unit. According to Betor, the fork—supplied now with its own triple clamps—should go right on, though at first DG had to bore out the stock Suzuki triple clamps to accommodate the 28mm Spanish tubes. While the $225 fork is supplied with triple clamps and air-fork caps, you still need S&W fork springs ($12.95) and two sets of booster springs ($3.95 a pair). In each leg, you use three springs, six ounces of 10-weight fork oil, and about 13 psi air pressure; this will set the front end up for riders who weigh in at around 120 pounds.

Good rear suspension begins by throwing out the stock swing arm, swing-arm pivot bushings, and shock absorbers. The bronze DG bushings are solidly (not rubber) mounted in the swing arm, so that the swing arm waggle is eliminated. Sold separately, the bushing kit is $8.95. The aluminum swing arm adds two inches to the wheelbase, which slows the handling down and makes the mini feel a lot more stable. Taking out some of the snappiness in the RM80's handling is a good thing in any case, and especially so when the horsepower is bumped up to the max. The swing arm is more than a safety item, however; it permits the use of any number of 13.5 inch shocks, and rear wheel travel will be increased to 7.5 to 8 inches, depending upon what shocks the rider selects. Furthermore, the DG swing arm can accommodate an !RC 4.10 x 14 rear knobby—something beyond the capability of the stock arm. The aluminum DG swing arm, which includes the chain tensioner, is $129.95.

The forward-mount chain tensioner ($21.95 separately) actually mounts to the frame, and exerts a light tension on the chain via a long arm and roller. The arm is designed to apply pressure at the center-point between the two sprockets. The light tension won't drag the chain nor wear out the roller prematurely. The roller actually turns on a very wide plain bearing surface (aluminum to steel), and two rubber 0-rings seal the bearing area.

DG has received positive customer feedback about Arnaco shocks, which use the standard shock mounts. Arnaco shocks retail for $109.90, and the springs are $23.95. S&W, Boge Mulholland and Girling gas units are all less expensive alternatives.

The complete DG racers have their frames strengthened. Double-wall front engine mounts are used; gusseting is added to the frame under the tank, where the upper and lower frame rails running back from the steering neck tie together; and the pivot-pin area is beefed up with the addition of 1/8-inch steel plate positioned under the footpegs. A bike subjected to hard use without these modifications is likely to break its frame; with the mods the frame integrity is adequate, but sometimes engine cases will fracture in the area of the front engine mount.

For wheels, the DG race bikes use domestically-produced K&L rims (WM1 x 16 or 17-inch front and WM2 x 14-inch rear) at $32.95 a hoop. You can string your own with DG-supplied eight-gauge spokes ($19.95 per wheel), or simply buy the complete front wheel and rear wheel kits for $88.95 apiece. To cover the rims you'll need IRC tires, 4.10 x 14-inch at the rear for $20.95 and 3.00 x 16 or 17-inch at the front for $18.95.

Beyond the hard-core hardware, there are a lot of RM80 accessories that are nice—but somewhat optional-extras: a seat kit ($19.95), trick fenders ($12.95), side plates ($14.95), fork protectors ($8.95), chrome moly bars ($19.95), crossbar pads ($2.95), and even a gas cap ($10.95).

The stock RM80 is a mild, mild engine, with about a 120 degrees of intake duration and 175 degrees of exhaust duration. It gives a short burst of low-end power, and it's dead reliable for a season of racing. The dyno chart indicates what a stock, but carefully assembled, RM80 will produce.

DG offers different stages of tune: an Intermediate Kit ($164.95) and an Expert Kit ($269.95). Obviously the DG Team bikes follow the latter set-up. As the first step, the transfer ports are properly aligned; the bottom of the intake port is dropped four millimeters and the top of the exhaust is raised one millimeter; eyebrows are added to the exhaust port to hasten blow-down, and the transfers (except for alignment) remain the same. The standard RM80 piston is left untouched.

All internal passages of course are smoothed out and polished. On the intake side DG fits a special small-body 30mm Mikuni carburetor; there's no room for the big-body Mikuni. This small Mikuni is very trick indeed since the needle, jets and slide are all peculiar to the RM80 set-up. The standard steel reed-valves are changed over to linen reeds ($9.75 for a pack of five) which won't eat an engine should they disintegrate.

The huge aluminum sunburst head has 40 percent more fin area than the stock cylinder head, which is, among other things, notched on the right side to make room for the stock upswept exhaust system. Calculated compression ratio is 9.2 to 1, whereas the standard compression is a low 8.5 to 1. A stock RM80 has a squish band clearance of .080- to .090-inch. DG, with their own gaskets, works much closer, varying between .040 and .060-inch, depending upon individual cylinders. Forty thousandths 'is the recommended figure.

With the increased cooling area the DG bikes can use more ignition advance, more compression, leaner jetting and hotter plugs before seeing signs of terminal detonation. The engine can simply be tuned nearer the limit, by design or accident, than would be possible otherwise. DG bikes always use Castrol R40 in 20:1 gas/oil premix.

The expansion chamber used on the DG Team bikes is not quite the same as sold in 1977 in the Expert Kit. The team riders used a pipe that would allow the engine to spin upwards of 13,000 rpm. This in turn stresses the small end needles so severely that the cages fail. The small end bearings were changed almost on a race-by-race frequency. However, new RM80's come with much improved small-end bearings, which, on the basis of current DG testing, appear to withstand sustained 13,000 rpm loads. When the reliability becomes a demonstrated fact, the '77 team pipe will almost certainly become available. The current Expert pipe produces a slightly lower power peak (about 1000 rpm down on the team pipe) and offers a broader power band, more suitable to most mini-motocross experts.

Mototek ignition replaces the stock ignition system which was never intended for huge load, high-compression applications. The Mototek system, complete with coil and brainbox, is a straight bolt-on affair. It has a milder retard curve than the stock ignition, but more important, the Mototek delivers more spark energy. The voltage at the plug, for example, is double the standard system. The Mototek carries a 12-month guarantee.

The standard RM80 Suzuki gearbox can stand the increase in power without any modifications. The stock clutch springs can't, so the tuning kit includes heavy-duty clutch springs.

Beyond speed kits, any rider will need appropriate gearing so that he can match the engine to any specific track. Standard gearing won't come close in most cases because the power bands of the DG engines have been moved up so dramatically. Thus, the rider may well need engine sprockets (11, 12 and 13 teeth at $6.95 each) and rear wheel sprockets (48 through 53 teeth at $17.95).

The Expert engine is not a toy for an inexperienced youngster. The unit comes on like a light bulb, makes an impressive amount of horsepower over a narrow rpm band, has an astonishing peak output and signs off in a flash. It's important not to over-buy for a youngster. A full-tilt engine could not only be intimidating and stall a rider's progress, it could also be a body-breaker. Most parents can't understand how difficult it can be to ride a high-pressure mini-motocrosser, because adults don't fit the machines and therefore never really try to ride them. Finally, expensive high-performance equipment must be maintained properly, and that can't be handled by a dealer on an irregular basis. It means that the youngster or adult must be responsible for maintaining the bike; that takes more than a passing knowledge of motorcycles.

But then again, anyone who is likely to pick up a phone to order an $1800 mini-crosser, is—by that act alone—committed.■