The Motorbike Archives

Last March, AMA Professional Don Emde shattered the old school when he won the Daytona 200-mile National Campionsliip road race. The four-strokes had finally been beaten at Daytona, and to add insult to injury, they were soundly thrashed by a two-stroke twin of less than one-half the allowable displacement. Emde was riding a Yamaha TR3 which is a 350cc machine.

Comparing the TR3 and R5C is like making a comparison between American Motors' stock Matador ands the one Mark Donohue drives, you just can't. Yet there are some interesting similarities that should be brought out.

Both the R5C and TR3 are piston port twins. This means inlet timing is controlled by the skirt of the piston, There was a time when Yamaha, and many other two-strokes, used rotary disc valves attached to the ends of the crankshaft as a means to control their inlet timing. This was thought to be the best method to extract maximum horsepower, and in World Grand Prix road racing that's the name of the game. Technical advancements achieved through road racing has pretty much made this design obsolete for that type of competition. Spearheaded by Yamaha, most modern road racers are piston port-type engines.

R5C and TR3 engines are very close internally; they both use a 64mm bore and 54mm stroke. The R model gets 28 horsepower at 6,500 revolutions per minute while the TR3 has 30.2 at 9,000. Yamaha measures its compression ratio from the top of the exhaust port up, so their final figures are not as impressive as those found elsewhere in the industry. The RFC is 6.9:1 and the 1R3 is 7.4:1. The road racing engine is set up just a hair looser with its piston tolerances and uses a 34mm Mikuni, whereas the R5C is fitted with 28s.

Both engines transmit their power from the crank to the gearbox through a set of gears. The road bike uses silent raining helical gears and the racer's are straight cut to save a fraction of a "horse." Although we feel the R5C has a close ratio 5-speed trans, the TR model has one that is really close. (Six-speed gearboxes are also available for both the 250cc TD3 and 350cc TR3.)

The road racer nets out at nearly 70 pounds less than the R5C, yet we still found its 319 (wet) pounds to produce a very light feel while on the road during our tests. The bike feels right, is eager to go, and corners at the whim of the rider. This is the third year of production of the R5 models, and it's hard to believe Yamaha has made so few changes other than color and the style of the exhaust pipe.

Unchanged, other than a minor piston ring configuration and piston ring groove, is the R5C engine. This modern power plant follows all the basic engineering practices that we have come to expect from motorcycles produced in these complex times. A forged steel connecting rod has needles at the little end and roller bearings at the big end. The crankshaft is a series of forged and machined steel pieces that ride in four sets of ball bearings and is pressed together under tremendous tonnage. This adds up to a free spinning, low friction engine capable of producing many ponies.

Yamaha's Autotube, or oil injection system, is one of the modern conveniences we take for granted. The oil sump itself is driven from a squib shaft that gets its power via a nylon gear off the crankshaft's pinion. (When first introduced on some models, the pump was driven from the gearbox. If a rider was to have this particular model with the engine running while at a standstill, clutch lever in with the bike in gear, the oil pump would not be in motion. This never amounted to any problem, but it was a disturbing fact to those who realized what was going on.) The pump varies its output according to the amount of throttle that is being used. In fact, it has a cable hooked directly to the throttle linkage. Oil comes from a separate tank to the pump then piped to a set of fittings in the inlet manifold downstream of the carburetors. The 4% or 5% gas/oil ratio as required on the mix-it-yourself two-strokes is a maximum lubrication requirement. At half or quarter throttle the engine can live at probably 2% and this is what the variable output oil pump does. It delivers the amount of oil the engine needs in comparison to the amount of throttle being used. The engine emits less smoke and runs cleaner, and that's better for everybody.

The clutch is a normal multi-disc affair using two unlike materials under the compression of 6 coil springs. Dog-type engagement is used within the 5-speed transmission utilizing three shifting forks programmed through a drum-type shifting cam. The gearbox is smooth operating and trouble free.

Our R5 is a kickstarter-type and, with the richening lever in the "on" position, it stars dead cold with 2 to 3 tries. The Yamaha takes a minute or more to warm up before it will run with the richening lever off. The engines revs freely in neutral, emits very little noise, and doesn't vibrate much either. A magnetic/mechanical tachometer needle lazily points out revolutions per minute as the engine is blipped up and down the scale. A matching speedometer is mounted to the left of the tach and is thoughtfully equipped with a mileage trip odometer.

All lighting switches are controlled by the left hand. A small cast aluminum multi-switch housing fits between the clutch lever and handgrip. Lights, high/ low beams, turning flashers and horn button are all within easy reach of your thumb.

A long, softly padded seat blends into the fuel tank and terminates well behind the rear shocks. Its height is a little over 31 inches from the ground, a distance that fits most riders. Footrests to seat to handlebar dimensions fit the midi-size to small-size riders, but a bit close coupled for one of our 6-footplus grasshopper-type testers. He kept sitting on the passenger's hand holding strap.

Controls work with a light feel and the R5C slips into first gear with just a touch of the left toe. You've got to rev it a bit to get enough torque from the engine to get under way. Once in motion the machine accelerates hard, and if you overdo it the front wheel carries across the intersection waving in both directions and not making contact with anything. An effortless click into second gear, a lot of throttle, and you've exceeded the residential speed limit. The R5C is quick!

We found this 350 to have a rather long jump from first to second gear with the rest closely spaced. The upper four gears are ideally suited for fast touring on those delightful twisty back roads, the kind where you rarely need fifth. A 350 is about as small as one would want to go if he contemplates bringing a passenger along. A second set of footrests are well placed for the second rider and their comments were quite favorable during our tests. With two aboard the R5C is not as agile or quick but still runs faster than the flow of traffic on expressways, or in the city.

Muffling is very good on this twin with most of its running noises coming from the inlet tract or air filter housing. The Yamaha has a rather heavy inlet roar under hard acceleration.

Stopping the 350 is both effortless and fun. A large, self equalizing double leading shoe front brake will collapse the forks and all but smoke its tire under hard use. A rod operated single leading shoe rear brake will skid the rear wheel at any speed we tried. She pulls down well in a straight line with both controls being sensitive enough to take the tires to the brink of skidding without actually locking them up. Through all this we got the finned hubs warm, yet the brake lining refused to fade.

In conclusion we found Yamaha's 350cc R5C to be worthy of the title bestowed upon it by other members of the motorcycle publishing industry. It is an excellent medium-size touring machine, one that can be whipped around town and taken on those long, high speed journeys. The R5C is a good all around street motorcycle, and after all, that's what they made it for.■