Yamaha RD500LC

18 Июн 2015 | Author: | Комментарии к записи Yamaha RD500LC отключены
Yamaha RD 500 LC

Street going two-strokers in 1979 right. The Yamaha failed to return with the in the spring of 1980, and that was Extinct.

When the water-cooled appeared, first in Canada and in the United States, it wasn’t an rebirth just a cameo for those few dedicated RD-lovers, again? And the juggernaut of popular for big four-strokes rumbled ahead Two-strokes were still

Emissions had … them public lust for big four-strokes had them twice, and now the grass was on the grave.

Two-… technology … — it just seen on the street-bike side of the floor. What about torque-laden motocrossers, light as and factory road racers wonderful 4000-rpm powerbands and the of a good four-…? Yes, was progress aplenty, but it was invisible to riders.

On the other hand, scrap of four-… streetster was instantly on sale and ready for delivery. Now how about all that bottled-up two-… progress? kind of street bike all that make?

Don’t tax imagination. Yamaha has now built the

This hot pipe dream to life is pretty much a replica of the factory Yamaha now leading the 500 road racing Championship. Like the OW, the RZ has an aluminum a V-four, two-…, water-cooled, engine, a sideloader gearbox, Valve cylinders, magnesium cases, and, above the look of the $1000-a-pound missile rolled so very carefully to start grids.

Pipes from everywhere, aluminum eye-trapping detail in the footpeg alloy foot controls, in team paintwork. Food for the sustenance for the imagination.

And not available in the At least not here, not yet. are Yamaha’s intentions? Unknowable now. Let’s not ask. gaze upon the parts.

The is light and powerful 413 pounds dry and 90 bhp. When the technology in, the weight came out out of every Road racing over the five years has been a of design competition, producing not innovation but also attention to making earlier work coarse. Engineers questioned use of material in this machine.

Fasteners are down-sized. Thinwall abound. Traditional parts oozed into new forms a bit lighter, easier to make and better in function. The result is a motorcycle weighing only 100 pounds more than its racer. See this forged kick-start lever folded away behind the fairing?

It nothing in comparison to the steel on the old RDs. And just as on the real covers have the official cast into them for the

The engine’s architecture is pure race. Two cranks each the big clutch gear directly any heavy, power-consuming jackshaft. them is a balancer shaft, all capped by the cover casting the four separate Power cylinders.

Below, the gearbox into the main casting the left, echoing the quick-change of current GP bikes.

The forward of cylinders lies horizontal, the pair inclines forward at 20 degrees from vertical. The enter from the vee while one of exhausts shoots straight from the rear cylinders and the sweeps up from beneath the

The 56.25mm iron-linered cylinders are to the crank-cover casting by their flanges, not by through-studs. This maximum freedom for generous port layout. Because the is only two cylinders wide, the can sit on the same 112mm centers give the current TZ250s giant, sweeping transfer arches.

The cylinders must be castings because of the way the Power are assembled in them, but the conventional heads are cast in pairs.

Is engine just a heavy of two old RD250s? If it were, it would over 160 pounds, but in fact engine, with its large is actually ‘ lighter the 120 pounds of the 1980-81 magnesium engine. Detail design has this.

Crank bearings solid support all the way across, gearbox shafts need carriage only at their This makes it reasonable to put the in one case split with its sections, and to put the gearbox into a whose ends are the only of substance. Each cylinder feeds its stress into a boss that carries it to the main bearing saddles, and the cases are only thick to keep the fluids and gases they belong.

Thick where they be, thin where they may be.

water-cooling heavy? Each of cylinders, even with its and Power Valve, is over a lighter than an air-cooled cylinder. Each RZ head in pairs) weighs only as much as the RD parts.

Added up it than pays for the pump and

On to the 50mm-… crankshafts. Their are seven millimeters smaller in than the old RD crank’s and two and a half lighter. Surprisingly, they are lighter than the current TZ Motocross influence shows in the deeply and smoothly scooped out the rod big-ends.

This provides for better than expensive holes and gives the intake an inviting space to head As on the 350LC, the hollow crankpins are with the inner wheels. The forgings are as economical in design and use as the TZ parts and turn on silver-plated cages as the racers’ always

Five millimeters shorter the racing parts, they for shorter and therefore lighter

Motocross also inspired the pistons. Instead of the lumpy, look of the old RD parts, behold the dense texture of racing The undersides of the wristpin bosses are next to the rod small-end because is less stress there. Why extra metal along for the ride? The keystone top rings are 1.25mm wide—a figure only in racing engines not so long ago.

The conical surfaces of these rings and eject carbon as the pistons preventing long-term deposition might stick the rings. The ring has the same width but is of section. Even the wristpins are The standard 16mm, they now larger, smoother holes them.

The old wristpin clips their tangs have and no one will mind having to use a to pull these new ones. No means nothing to break off your engine. TZ owners all about this.

Look down into the or up into the bottoms of the cylinders and be struck by the enormous volume This hints at the technology makes this motorcycle right now; philosophically RZ engine is far closer to the latest designs than to any past engine. Much has been in the last five years, and of it is right here.

After two-strokes were just substitutes for real engines— specials. As certain dedicated worked with them shed their dumpy and emerged as powerful if difficult The first winning designs of the had powerbands measured in hundreds, not of rpm.

Later they built with 10-, and even 18-speed gearboxes they desperately needed

Ports were small then, and pumping fresh up through them from the called for high crankcase ratios. Even today people, mesmerized by this mutter about crankcase

Small ports and high pressure combined to squirt the out of the transfers so fast it looped the cylinder and out the exhaust port at speed but one— peak the fast-moving piston could off the outflow before most of the had been lost. Good might result, but only high up. The simple pipe of that time made the worse, offering no apparent to the powerband problem.

For street the charge-loss problem was solved by port sizes and timings so almost no mixture ever in the cylinder so hardly any got lost those were the days of the 125s.

In time ports got and designers realized the exhaust was potentially a better and more pump for the fresh charge was the crankcase. With such pipes, capable of prolonged and suction, it turned out that with big, low-compression had better powerbands and were no powerful than the best of the engines. What a lovely

Yamaha RD 500 LC

The more mixture in the case, the there is for the pipe to draw the cylinder to scavenge and fill it. rises. At lower speeds, the case doesn’t squirt its quickly to the exhaust to be lost—it flows the mixture in slowly so much of it is trapped and burned for The RZ engine has the generous transfer area, the large-volume crankcase, and the high-suction exhaust pipes of a two-… racing engine.

power, good band good economy and moderate are the result.

Years ago, timings were the big secrets, but about 1960 everyone on figures that have essentially fixed. Only the and directions of ports have a racing engine opens its at about 79-83 degrees and opens its transfers about 35 later. A sport engine the exhaust at 85-90 degrees and its transfers 25-30 degrees

A trials engine may open the at 100 degrees and transfers 15-20 later.

Blowdown is the timing between exhaust and transfer and determines how much time is available for cylinder pressure (up at psi even after expansion by the …) to blow down low for transfer flow to begin. At rpm, the piston moves so adequate blowdown requires timing, but on the bottom, when the is moving slowly, a much timing is adequate too much only risk charge The Yamaha Power Valve, and lowering the top of the exhaust port, is a for changing this blowdown according to rpm: the engine like a racer on the top end and like a machine on the bottom—a very combination.

When the RZ’s Valves are fully open, the opens at 85 degrees ATDC as in the old RDs, while at the bottom of the it is opening at more like degrees ATDC. Why the RD-like Remember, this is a street not a racing engine.

It has do to things be easily ridable, get reasonable mileage, and even pass emissions standards one day. It necessarily do all these things yawning exhaust apertures. The advantage over the old RD comes the size more than the timing of these holes. The exhausts were only wide, but these new ones are a 39mm—only one millimeter less those of the current TZ250 racer’s.

That’s 70 percent of bore something we were told just a few years ago was impossible ring snagging. Well, has built a lot of wide-port MX and road engines since those and has learned a thing or two. port shape is gentler in the rings back into grooves after the bulging across the port, and, ring materials accept service without snapping.

ports open a whopping 38 after exhaust opening, so is plenty of blowdown for 10,000-plus rpm here. The transfers, opening at 123 ATDC, are rather late in with racerly numbers of degrees, but higher transfers in turn require higher and soon the RZ would just be a race engine. Watch the move toward BDC; it only part of the transfer windows.

This means is plenty more to come this engine in the future.

from all this huffing and reaches the six-speed gearset a big wet clutch whose plates the same dimensions as those of the racer. Any engine whose don’t all lie in a single horizontal split has a gear lubrication How to lube the shafts and gears at the top of the

Submerge those at the bottom and oil churning losses are bad enough, running to many horsepower, the oil foam right out the breather all that gear action. answer is to put a small Eaton-type lube pump at the bottom, oil from the sump area the shift-drum and delivering it in correct to the several meshes. The pump far more power than it for now the transmission is well lubricated heavy churning loss.

On modern GP road-racing engines a can pull the dry clutch in about minutes while his helper the lower pipes and drains the oil. The tuner pulls the cover while the assistant the drive sprocket in another or 10. Unbolt the door holding the cluster into the gearcase and the whole thing out shafts, shift-drum, and selector forks. Lay it out on the and exchange ratios to tailor the to the circuit.

In under 40 minutes, the is rolling back out with the ratios. Obviously at the Grands this capability is essential. The RZ is in similar fashion, but for a different

A compact V-four cannot be as a single-case-split engine, so this sideloader construction is the most way to carry the gears. Remember, that Harley-Davidson motorcycles had construction for many years it became popular at the GPs.

The RZ rendered in street-bike fashion, has dogs at each engagement to cut on backlash, something that riders have been to worry about. In racing, dogs or even two make sense because the primary is strength and quick, certain Few dogs and big spaces between give you this, but they give the backlash that folk don’t want.

are the RZ’s dogs undercut as in a real race engine certainly be. In racing this the gears into engagement and them there during clutchless shifting. On the street, design is not yet accepted.

Truly however, are the extremely close separations, almost identical to a TZ750’s:

Yamaha RD 500 LC
Yamaha RD 500 LC
Yamaha RD 500 LC

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