Ask Kevin Cameron: Hard Riding Beasts — Yamaha TZ750

15 Апр 2015 | Author: | Комментарии к записи Ask Kevin Cameron: Hard Riding Beasts — Yamaha TZ750 отключены
Yamaha TZ 750

Ask Kevin: Hard Riding – Yamaha TZ750 KC answers his fans’ request for more on the TZ.

the AMA announced that for 1972 the limit for racing motorcycles be 750cc for all engine types, and Kawasaki had three-cylinder production ready to be re-engineered into 750 Yamaha had no such model and so soldiered on with its latest two-… Twin, winning in 1972 and ’73 after the ill-handling, 750 two-… Triples had spun old-technology tires to shreds.

The EPA had to regulate automobile exhaust so it was obvious that smoky had a short market future. being so, Yamaha did not produce the GL750 inline-Four it had readied as for Kawasaki and Suzuki.

Yamaha had surprises ready. One was a 500cc Prix bike, the 0W20, on the GL750 architecture. This was two of Yamaha’s racing 250cc set side-by-side, each with a gear on the inner end of its crank and pair of gears meshing a double-width gear on a jackshaft to drive a dry clutch on the right.

as with the Twins, each of cylinders was made as a single block, but unlike the piston-ported this 500 had cylinder reed-valve All four exhaust ports forward, and four smallish were crowded together to under the engine.

It was on such a that Finn Jarno won the first two GPs of 1973.

After … at Monza in a smaller class, Yamaha withdrew the and began planning for 1974. to this plan was to hire Agostini away from the MV Agusta team for whom he had since 1966. Yamaha now a larger, four-cylinder, 694.9cc two-…, coded 0W19, would debut as the TZ750A in the in March at Daytona.

Australian Kel Carruthers, tech of the American Yamaha race went to Japan to try the new machine. it had been deliberately given the short 53.5-inch wheelbase by Agostini on his three-cylinder MVs, but found the bike to be unstable at speed. His remedy was one that had for him on other fast motorcycles: to the wheelbase with a longer

A 3-inch extension did the job.

is a difficult place to introduce any new because the combination of sustained speed, extra loading the banked turns and the 200-mile distance conspire to frustrate ambition. Running on Dunlop’s new belted-bias Speedway Special tire, Ago survived challenges and not to damage his tires on the sharp of cracked-to-pieces Yamaha exhaust

Like the 500 GP bike, the new TZ750A’s pipes were crowded under the engine, and as 10,000 pulses per minute hit each pipe, they tried to it to roundness. The resulting flexure the track with broken and left Ago’s bike a harsh open blare. Yet he won the

TZ750s would win the race year from 1974 to ’82

TZ750As were twin-shock with a swingarm made sheet-metal pressings. When the AMA got to Talladega, many big TZs were unstable at speed. I saw more one rider take to his lawn white-faced and shaking.

Some actually decided 750 roadracing was not for them and went to 350cc Twins.

The instability had a and it was not 750cc but rather little circlips, whose grooves not deep enough to keep in place. When these popped out, either one or fork damper units damping and terrifying high-speed began—a violent Dutch at three cycles per second. Don Yamaha team bike his feet right off the pegs before start/finish in Friday

On Saturday morning, Carruthers had the ends off all three team found the problem and fixed it.

750s were not easy to because two-… power not come in smoothly and progressively. as the rider turns the throttle, much happens initially, by irregular popping that eight-stroking, then four-stroking and continuous firing. Because the is big, these changes are and the rider must be ready for

The irregular firing occurs in all two-strokes, big and small, because at throttle, the cylinder is mostly with exhaust gas. little mixture entering, it several revolutions to accumulate charge for the sparkplug to ignite it. is no problem on a 125 or 250 because the torque are manageable. But if you try to throttle up from lean on a 500 or 750, the engine yank the rear tire and you will go sideways.

If the tire re-grips gently that you don’t highside, the is “only” a big gollywobble. If you are determined to on, you will do so in an off-corner weave, by a series of near highsides.

were horrified by this, but came Yvon Duhamel, for his bronco-riding ability, in from And he was saying, “I think it’s a little better now,” but you just seen him wobbling and and can find no meaning in his words. He what he was talking about.

enabled him to ignore “normal” to concentrate on detecting actual to stability. Attempts to make the smooth just slowed the down. And there were of slow riders on TZ750As, sold for $3600 before 1974 Daytona.

In 1975 the “Full Size Kit,” increased bore from to 66.4. In the kit were cylinders, pistons and new cylinder nuts original blue anodized broke frequently, one of them Kenny Roberts from a win).

In 1976, the factory the 0W31 monoshock 750, its Vincent-style triangulated swingarm. was another important step solution of 750 handling problems. big, round tire and slicks—were a first step, but up weak chassis elements the twin-shock swingarm was next. And rear-suspension travel, an essential of the monoshock idea, was the third.

long travel, softer and damping rates could be which kept the tire on the more of the time, not hopping in the air as it did the stiff, old, 3-inch-travel orthodoxy that dated to the 1940s.

Despite that, watching the short straight before Turn 5 (leading from the up onto the banking), I could see tire and damper deterioration was the leading bikes to weave even in middle gears.

Yamaha TZ 750
Yamaha TZ 750

At the Trans-Atlantic Match Races, Baker showed what was possible by sensationally wheelying out of corners. Control! In 1978 at Bud Aksland said, “Look as he depressurized one of Kenny Roberts’ suspension units, then the gas reservoir and poured out the “oil.” It was a emulsion of leaked gas and oil, with dark wear from damper piston, and seals.

Later, Roberts was inJapanand finding it hard to get Often the problem is too much damping, which lets knock the whole machine instead of just the tire. A in the air means no grip and no stability.

But the compression damping didn’t do so, at length, Roberts said, “Is damping in a part of the damper we can just leave out? Can we do away with compression completely?”

After some a damper was assembled with a in place of its compression valve. Roberts tested with his lap times immediately improved. quickly, having a much-bigger valve, capable of letting the wheel move really became essential to good Geoff Fox was an important pioneer in but everyone quickly adopted the

With a bigger compression it was no longer necessary to gear bike so you could upshift as it hit the out of Daytona’s Turn 5. You could the power on across steps or pavement. More control, of the time.

Kayaba’s 36mm on the TZ750 was designed for the grip of triangulars of the classic “hard era.” With slick it became common for fork to allow the brake discs to the brake pads back in the When you got to the next turn and for the brake, the lever came to the What a disappointment!

That a move to bigger and tubular axles and to bigger, stiffer tubes.

As tires got bigger, made changes to its factory moving the chain line to the away from the tire, and frame-tube positions. Privateers production versions used a wet blade held in Vise-Grip to carefully—very carefully—pare away the shoulder of the tire. This it obvious that tires going to grow (a 250cc GP of 2009 wore the same rim and sizes that looked so to us in 1974), so designers had better room for them.

Front coned under the heavy of twisty circuits like and Sears Point, pushing back in a different way. made it clear that must be flexibly mounted to carriers so they were to expand without coning.

Finally, in 1982, Honda was to take a swing at Daytona a designed-for-the-job 1000cc V-Four (Formula 750 had been changed to 1025cc four-strokes). The FWS1000 had one of the back-torque-limiting “slipper” clutches so its braking would not upset entry with hopping and

It should have been a but the race was won by Graeme Crosby on a built-from-parts 0W750. Roberts, the leader on a 500cc GP bike, was out a tightened engine. And the giant needed to stop too often for

This was the last Daytona 200 win by the TZ750 design.

The 750cc era had with wild drama, but change had gradually softened the of its problems, preparing tire, and suspension solutions that be ready when, in the later and ’90s, powerful, lightweight began to enter production.

Got a or request? Visit Kevin on Facebook and ask him.

Yamaha TZ 750
Yamaha TZ 750
Yamaha TZ 750
Yamaha TZ 750
Yamaha TZ 750
Yamaha TZ 750
Yamaha TZ 750


Tagged as:

Other articles of the category "Yamaha":

Our partners
Follow us
Contact us
Our contacts

Born in the USSR


About this site

For all questions about advertising, please contact listed on the site.

Motorcycles catalog with specifications, pictures, ratings, reviews and discusssions about Motorcycles.