Post by revolver on Mar 11, 2012 5:22:49 GMT
Yamaha’s FZ750 was possibly the biggest leap forward of any Japanese motorcycle ever. Just 12 months after Kawasaki’s GPz900R had seemingly secured the title. 25 years on much of the FZ’s design remains a blueprint for motorcycle engineering.
1985 was Year One for modern motorcycling. OK, so Kawasaki’s GPz900R had sort of got things started the year before, but we’d had water cooling since the Scott Flying Squirrel. And 16 valves since the Honda CBX1000.
But Yamaha’s FZ750 was something very special. Yamaha were late to the four-stroke party and even later to get their tech heads into gear. But this one, the Yamaha FZ750, really did go up to 11. The redline of that wonderful 20-valve engine was 10,500rpm, but the clever cylinder head design let it hold onto power for another 500rpm or so after that.
In fact, by most measures of the time, Yamaha’s FZ750 went up to 12, so radical and innovative was the thinking in that all-new engine. We didn’t know it at the time, but Yamaha were laying the foundations for the second generation of Japanese motorcycles. The FZ wasn’t officially part of the Genesis family (that started with the F1 race bikes and then the FZR1000 in 1987 and was all about a philosophy of building bikes as one – no longer an engine and a chassis), but much of what came next started in the FZ750.
Launched a year after the GPz900R, the FZ750 was Yamaha finally joining the big time. Previous Yamaha four-strokes had largely been clones of other Japanese bike or old British knockers. The XS range never really delivered and the XJ’s, good though they were, were eclipsed by the Hondas and Kawasakis of the day.
But the FZ was different. It blew Honda’s ‘vision-of-the-future’ VF range away. It made the GPz look like a stop-gap and even Suzuki’s all-new GSX-R seemed just a conventional motorcycle made with futuristic materials. The FZ had the engine of the future and a semi-beam frame that hinted of what was to come. The front suspension talked of ‘compression damping’ when others still spoke of anti-dive. Swapping the position of the fuel tank and airbox meant the mass was more centralised and having the engine canted forward gave the right weight distribution for better handling. Yamaha – a confident company who’d dominated recent two-stroke design were showing the same innovative thinking in four-strokes. They’ve been leading the field ever since.
1 It was Yamaha’s first four stroke race replica. ‘A four stroke in the RD mould. An F1 racer with street equipment,’ they said at the time.
And funnily enough for a 205kg bike, it felt like it too. The riding position was RD-familiar, the clocks had an RD-feel and the cowled tacho felt terribly cool.
2 It set the rules for a generation of sports bikes. An inclined engine gives a straighter, faster path for air and fuel into the cylinder head. Reversing the position of the fuel tank and airbox allowed a bigger airbox and the fuel to be carried lower and more centrally, while pumping fuel into the carbs allowed the use of downdraught units for more power.
3 The project started in 1977. By this time the two-stroke was all but dead in America – the world’s biggest motorcycle market. Yamaha needed to get four-stroke serious but were lagging behind. Even the newly launched XS range was outpaced by the competition. The prototype was codenamed ‘Project 064’and was a 16-valve, air-cooled machine. No one remembers what 63 and 65 were but this was the big one.
4 Five valve heads allowed optimum cylinder head design. Yamaha, like everyone else at the time were looking for the most performance and better fuel efficiency. They reasoned that simply increasing the valve sizes on a four valve engine would mean a flatter combustion chamber when the perfect shape is a hemisphere. More valves allowed the use of narrower valve angles, which permitted a ‘hemi’ shaped head with a smaller volume than other heads for increased compression ratio. More valves also gave a larger intake area and better gas flow without needing large degrees of valve lift that could have been unreliable. And using more, but smaller valves meant they could be lighter. Which meant higher valve speeds and more rpm for increased power. Lighter valves also meant lighter valve springs for less flutter at high rpm, better seating and less power loss in valve train operation.
5 But they also tried six valves. Which didn’t allow the right combustion chamber shape and the central exhaust valve was exposed to excessively high temperatures.
6 And seven. Four inlet (including one in the middle, three exhaust valves and two spark plugs (one either side of the central inlet valve).Which gave even better gas flow but less flexibility and had a 20,000rpm redline. These were the days when Yamaha were involved in building Formula One engines so anything and everything was tried. Seven valves worked but they were worried that they couldn’t mass produce such a delicate engine.
7 And a V-four. By the early 1980s Yamaha were already developing their V4 two-stroke GP bike. They understood the benefits in packaging, weight distribution and traction from a V4 but eventually went for an inline engine to keep production costs lower. By the time they got to prototype number 11, built as a racer, the engineers were getting 130bhp from 749cc and 25 per cent more torque than from the two valve engines still being developed for the XJ and FJ ranges.
8 Downdraught was the future Yamaha were also developing their V-Boost system for the V-Max. This system, effectively a twin-choke downdraught carb for bikes, required the airbox to move in front of the fuel tank and to sit directly above it. Yamaha’s engineers discounted V-Boost for the FZ, but adopted the downdraught idea to give more gas at higher speed to an engine that wanted to rev. Bike number 11 was adapted in 1983 to be the basis of a new roadster. Detuned to 100bhp for reliability. Yamaha were there.
9 It was the genesis of the ‘Genesis concept’ Yamaha’s Genesis concept defined sports bikes of the late 1980s but it wasn’t about just having five valve-heads or alloy beam frames.
Genesis was about designing the motorcycle as a whole – getting away from the traditional Japanese problems of too much power in not enough chassis. The FZ750’s engine and chassis design worked as one.
10 And the steel frame’s last stand. Suzuki’s GSX-R might have had an all-alloy cradle frame but it was still essentially the same design as your dad’s old Norton. Kawasaki had used a spine frame on the GPz, but the future was Yamaha. The FZ’s frame spars came out and around the engine. Still high, like a cradle, but it was the beginning of the beam frame. The next generation wore their frame spars lower and wider to give more room for bigger airboxes. And after the FZ, it was all alloy.
11 Within two years it was obsolete. Such was the pace of development at that time. Honda’s 1986 VFR750 had an alloy beam frame, and a V-four 16-valve engine that made almost as much power and better midrange. Kawasaki’s GPX750 made the same power from a 16-valve engine in 1987 and Bimota’s YB4 showed everyone the future of chassis design. The competition was learning fast. The FZ became the FZR1000 in 1987 – a proper race replica with an alloy beam frame plus suspension and brakes from another world.
12 But in racing, it was still good enough to get Eddie Lawson his first Daytona 200 victory in 1986. Lawson finished more than a minute ahead of Kevin Schwantz. It also won British Superstock in 1987. FZ750s filled four of the top five places and seven of the top 10 in British Superstock. Keith Huewen won the title by 35 points from Roger Hurst, also on an FZ.
13 Harris built the fairing lowers. By 1986, half fairings were for losers no matter how pretty your engine looked. Yamaha needed a full fairing and Yamaha UK approached Harris Performance to build some as a £300 option. By 1987, Yamaha
had redesigned the FZ as a fully faired machine.
14 It was the future of front suspension. Yamaha ignored the fashion for anti-dive front forks and instead talked of variable self-adjusting compression damping – essentially a valve in the front forks that controlled the oil flow depending on the rate of travel.
15 But not at the rear. The single shock fitted to the FZ had adjustable preload and rebound damping, but the preload was adjusted by a small chain, similar to the early RD350YPVS. And just like the RD, the chain would break after one winter’s use.
16 The oil light measures level, not pressure. Like most Yamahas up to the mid-1990s. So when the light comes on, chances are it just needs a top up, not a bottom end rebuild.
17 In seven years’ production there were only two official updates. The 1987 revamp got a full fairing, four-into-one exhaust, minor engine modifications to reduce friction and a milder exhaust cam. A new rear shock absorber and revised linkage to give more wheel travel, revised fork internals and solid brake discs. The 1991 revision brought new wheels including a 17in front, bigger discs and four-piston front brake calipers from the FZR1000.
18 Decent aftermarket exhausts are scarce. Motad’s race pipe added 10bhp if you also raised the front of the fuel tank half a centimetre. But was loud enough to deafen Lemmy. Motad don’t build noisy pipes for the road and the limited numbers they built for racing were very carefully controlled. But some of the handcrafted pipework did escape the paddock and (literally) caused headaches for both riders, villagers and coppers everywhere.
19 It had the longest bar-end weights we’d ever seen. No one knows why – the FZ engines aren’t especially vibey. But plonking your hands on an FZ’s bars was a very different feeling. Slim grips and a lot of metal sticking out. Thankfully the riding position was spot-on.
20 It revved to 11,000rpm, but was also a longer stroke engine than the GSX-R or VFR. Long stroke means better midrange but also high piston speeds and usually lower redlines. Thankfully, the FZ was built to last. The smaller intake valves were also 20 per cent lighter and that, coupled with the downdraught technology allowed the Yamaha to make more power throughout the rev range and hold onto it for longer. At 7500rpm, the FZ made 15bhp more than Suzuki’s GSX-R750.
21 And made more power than any of the 750s. Even by 1987, against Honda’s VFR and Kawasaki’s GPX, the FZ was still the most powerful (just) 750 with 90.6bhp at the wheel. The GPX made 90.5bhp, the VFR made 87.7bhp and a GSX-R made 88.3bhp.
22 It was the fastest accelerating 750 too. Despite weighing 29kg more than a GSX-R, the FZ’s flexibility and power advantage made it a tenth of a second quicker over the standing quarter mile. 11.3sec for the FZ, 11.4sec for the Suzuki.
23 And the fastest top speed. The Yamaha managed 148.7mph, compared to the GSX-R at 145.5mph, VFR at 143.1 and GPX750 at 146.9mph.
24 Valve clearances were 28,000 miles apart. Because the lighter valves were less stressed and less likely to go out of adjustment, the service intervals could be longer.
25 In 10 years time they will be expensive. FZ750s are cheap right now. Hacks at best, but many have been cruelly streetfightered or just left to rot. Unfair because this is a landmark motorcycle. The first of a new generation and possibly Yamaha’s greatest ever road going moment.
Make Model
FROM THE WEBSITE:http://www.motorcyclespecs.co.za/model/yamaha/yamaha_fz750
Yamaha FZ 750 Geneses
Year
1986
Engine
Liquid cooled, four stroke, transverse four cylinder, DOHC, 5 valves per cylinder.
Capacity
749
Bore x Stroke 68 x 51.6 mm
Compression Ratio 11.2:1
Induction
4X 34mm Mikuni carbs
Ignition / Starting
CDI / electric
Max Power
105 hp 74.4 kW @ 10500 rpm (rear tyre 94 hp @ 9400 rpm )
Max Torque
81.4 Nm @ 8000 rpm
Transmission / Drive
6 Speed / chain
Front Suspension
Telescopic forks non adjustable.
Rear Suspension
Monocross with single shock adjustable for preload.
Front Brakes
2x 270mm discs 2 piston calipers
Rear Brakes
Single 270mm disc 1 piston caliper
Front Tyre
120/80 V16
Rear Tyre
130/80 V18
Dry-Weight / Wet-Weight
209 kg / 222 kg
Fuel Capacity
22 Litres
Consumption average
38.3 mpg 16.3 km/lit
Braking 60 - 0 / 100 - 0
- / 35 m
Standing ¼ Mile
11.3 sec / 116.3 m
John Nutting fails to exercise his constitutional right to remain silent after crimes against the red line aboard Yamaha's FZ750...
The head honchos at Iwata will be the first to admit that Yamaha haven't had a very good decade, so far. Corporate enthusiasm tuned to beating the daylights out of Honda turned sour when it dawned on the Yam execs that Yamahas are not Hondas in the minds of punters. The name Honda is virtually synonymous with motorcycle in most parts of the world and Yamaha found to its cost that to attempt to break the mould is just a recipe for breaking the bank. In a word, Yamaha sales slumped.
The repercussions of the collapse echoed long after the replacement of the company President. Revised plans were initiated to put the company back on its feet; a degree of caution characterised the approach. British importers found that, despite the enthusiasm for the RD500LC and the FJ1100, the men from Iwata were sceptical of sales potential, so model allocations for Britain were low, reflecting the squeeze being applied at all levels, not least in the PR department. The result was that Yamaha caught a little bit of a cold in that sales of these two highly desired bikes didn't reach their full potential.
It's not a mistake the factory intends to repeat with the FZ750. Yamaha claim that the 5-valve in line four is to be a cornerstone of their range for the next ten years. A touch of cynicism might be acceptable here; after all, the bike trade has seen the pace of change accelerating by the second over the last two to three years, to the extent that to dwell on a new model for any length of time is to miss the impact of its successor.
But in an age where 'planned obsolescence' is translated into barnacled cam lobes and anaemic cam chains, Yamaha is keen to impress on us the longevity of this new engine, quoting oil-change intervals of 7,500 miles (!) and valve gear that'll only need the once over at 25,000 miles (!!) It all seems to good to be true, but if it is, we're on the way to the maintenance-free machine.
Like the Suzuki GSXR750, which we've yet to try out, the FZ750 makes a claimed lOObhp. That gives the hike a specific power of 133bhp per litre, putting it above Kawasaki's GPz900R's 125bhp/l, and it is only beaten by Honda's VF500F vee-four's 140bhp/litre.
Without the means of substantiating that claim on a dyno the only way of finding out if Yamaha were good as their word was to give the bike a good thrashing in Portugal.
Result was that it clocked 145mph at 10,800rpm in top gear on a deserted road south of Lisbon. By any reckoning that's pretty good for a 750 and it relates well to the 137mph top speeds accredited to the 90bhp 750's.
Now this top speed may be connected to the bike's remarkably slim profile. Long proponents of the idea that across-the-frame fours should be as narrow as possible, Yamaha has gone a step further with the FZ by exploiting water-cooling so that the pots are closer together and disposing of ignition components on the end of the crankshaft by using the end faces of the outer crank webs as part of the pick ups. Overall width of the motor is just 16.3 inches, less than the factory's own Japan-only air-cooled XJ400 four and about the same as Honda's vee-fours.
The speed may also be something to do with the neat fairing, claimed to offer a drag coefficient of just 0.34. It is certainly to do with power, and what's interesting is that it hasn't been attained by sacrificing flexibility. Though the FZ750 makes its best power over 7,000rpm, storming out of corners with the rear wheel drifting, it still pulls well from a walking pace in sixth.
This is where all the criticism of the complexity of five-valves-per-cylinder hits a block. Ten years ago we had 750cc racing engines putting out 90bhp if they were lucky, and only then with power bands a couple of thou wide valves. Valve springs need to be stronger to keep the cam followers on the cams without damage.
Four-valve layouts have gone a long way to raising the mechanical limits and improving the combustion chambers shapes which ideally should be a simple sphere. Honda first used four valves on its racers of the sixties to lighten the valve gear and raise the rev limits. But combustion was poor because of the awkwardly shaped piston crowns.
Yamaha claims to have tried to obtain the perfect combustion chamber with a seven valve arrangement that offered 20,000rpm limits. But, as you'd expect, fitting this number into a small combustion chamber proved too expensive for a production machine and eventually after trying six valves, five valves offered the best compromise.
The benefits are broad. By laying out the three inlet valves so that the middle one is out of line, and at a different angle from the cylinder axis, but still operated from the camshaft by a bucket follower like the other two, the combustion chamber shape needn't be complex. Indeed, Yamaha claims an 11.2 to 1 compression ratio which is remarkably high and shows that the combination of a slightly dished piston crown and centrally placed spark plug in a symmetrical chamber is the way to go.
Three small valves can flow more air than two and in the FZ's case they need less lift and opening timings to achieve it; that's the reason why the motor is more flexible than you'd expect. The three valves are individually lighter, so the point at which they start to float is higher up the rev range. Yamaha placed the red-line of the FZ at 1 l,000rpm with a rev limiter operating at 1 l,800rpm.
Because the valves are lighter, they need less strong valve springs so not only is the power absorbed by the valve gear lower, the camforms needn't be so radical. Wear is reduced as a result.
Straight, uninterrupted inlet ports have always been the goal for obtaining high power from four-strokes. Trouble is they're difficult to fit into bikes without getting in the way of the rider. But at the suggestion of the race team during the FZ's early development the engine was laid forward so that the air box was where the front of the fuel tank would have been. This meant that both the inlet ports would be straight and the spacious airbox got large helpings of cool air.
Yamaha's engineers say that the first prototype engine developed 130bhp at 13,000rpm, a not unlikely figure because they're claiming 330bhp at 13,000 for their two-litre vee-six car racing engine, and the production lump needed detuning for the road.
On the road, the FZ is smoother than most straight fours and as expected the hydraulic clutch and six speed box are slick, though at the expense of slack in the drivetrain at low speeds.
It's also very low with a sporting riding stance that tucks the rider behind the screen sufficiently well to keep his helmet out of the breeze. Steering is light and vice free despite the use of a 16-inch front wheel, a remarkably steep steering head angle of 64.5 degrees and short trail of 97mm. This is possible because, says Yamaha, pushing the engine-forward puts more weight onto the front wheel -almost 50 percent with the bike unladen.
For the scratchers, the news is that there's so much cornering clearance that they'll be in the gutter before anything hard drags despite the use of stickyish Dunlop Japanese tyres in fat 120/80V16and 130/80V18 sizes. The rear is an 18-incher so that racers can fit the more widely available slicks in this size.
Without doubt, Yamaha is hoping that this bike will form the basis of racers for the world endurance series and TT Formula events. With this in mind there's a tuning kit on the way that'll bring the power back to around 130bhp, making it more than competitive. In almost every respect, the bike's a detuned racer, but, like the RD500LC, the quality of the engine and running gear is such that it offers a refined package for the road.
Source Which Bike 1985.
I own one of these, I'm a demanding owner "- yet very satisfied that the above is the truth .
1985 was Year One for modern motorcycling. OK, so Kawasaki’s GPz900R had sort of got things started the year before, but we’d had water cooling since the Scott Flying Squirrel. And 16 valves since the Honda CBX1000.
But Yamaha’s FZ750 was something very special. Yamaha were late to the four-stroke party and even later to get their tech heads into gear. But this one, the Yamaha FZ750, really did go up to 11. The redline of that wonderful 20-valve engine was 10,500rpm, but the clever cylinder head design let it hold onto power for another 500rpm or so after that.
In fact, by most measures of the time, Yamaha’s FZ750 went up to 12, so radical and innovative was the thinking in that all-new engine. We didn’t know it at the time, but Yamaha were laying the foundations for the second generation of Japanese motorcycles. The FZ wasn’t officially part of the Genesis family (that started with the F1 race bikes and then the FZR1000 in 1987 and was all about a philosophy of building bikes as one – no longer an engine and a chassis), but much of what came next started in the FZ750.
Launched a year after the GPz900R, the FZ750 was Yamaha finally joining the big time. Previous Yamaha four-strokes had largely been clones of other Japanese bike or old British knockers. The XS range never really delivered and the XJ’s, good though they were, were eclipsed by the Hondas and Kawasakis of the day.
But the FZ was different. It blew Honda’s ‘vision-of-the-future’ VF range away. It made the GPz look like a stop-gap and even Suzuki’s all-new GSX-R seemed just a conventional motorcycle made with futuristic materials. The FZ had the engine of the future and a semi-beam frame that hinted of what was to come. The front suspension talked of ‘compression damping’ when others still spoke of anti-dive. Swapping the position of the fuel tank and airbox meant the mass was more centralised and having the engine canted forward gave the right weight distribution for better handling. Yamaha – a confident company who’d dominated recent two-stroke design were showing the same innovative thinking in four-strokes. They’ve been leading the field ever since.
1 It was Yamaha’s first four stroke race replica. ‘A four stroke in the RD mould. An F1 racer with street equipment,’ they said at the time.
And funnily enough for a 205kg bike, it felt like it too. The riding position was RD-familiar, the clocks had an RD-feel and the cowled tacho felt terribly cool.
2 It set the rules for a generation of sports bikes. An inclined engine gives a straighter, faster path for air and fuel into the cylinder head. Reversing the position of the fuel tank and airbox allowed a bigger airbox and the fuel to be carried lower and more centrally, while pumping fuel into the carbs allowed the use of downdraught units for more power.
3 The project started in 1977. By this time the two-stroke was all but dead in America – the world’s biggest motorcycle market. Yamaha needed to get four-stroke serious but were lagging behind. Even the newly launched XS range was outpaced by the competition. The prototype was codenamed ‘Project 064’and was a 16-valve, air-cooled machine. No one remembers what 63 and 65 were but this was the big one.
4 Five valve heads allowed optimum cylinder head design. Yamaha, like everyone else at the time were looking for the most performance and better fuel efficiency. They reasoned that simply increasing the valve sizes on a four valve engine would mean a flatter combustion chamber when the perfect shape is a hemisphere. More valves allowed the use of narrower valve angles, which permitted a ‘hemi’ shaped head with a smaller volume than other heads for increased compression ratio. More valves also gave a larger intake area and better gas flow without needing large degrees of valve lift that could have been unreliable. And using more, but smaller valves meant they could be lighter. Which meant higher valve speeds and more rpm for increased power. Lighter valves also meant lighter valve springs for less flutter at high rpm, better seating and less power loss in valve train operation.
5 But they also tried six valves. Which didn’t allow the right combustion chamber shape and the central exhaust valve was exposed to excessively high temperatures.
6 And seven. Four inlet (including one in the middle, three exhaust valves and two spark plugs (one either side of the central inlet valve).Which gave even better gas flow but less flexibility and had a 20,000rpm redline. These were the days when Yamaha were involved in building Formula One engines so anything and everything was tried. Seven valves worked but they were worried that they couldn’t mass produce such a delicate engine.
7 And a V-four. By the early 1980s Yamaha were already developing their V4 two-stroke GP bike. They understood the benefits in packaging, weight distribution and traction from a V4 but eventually went for an inline engine to keep production costs lower. By the time they got to prototype number 11, built as a racer, the engineers were getting 130bhp from 749cc and 25 per cent more torque than from the two valve engines still being developed for the XJ and FJ ranges.
8 Downdraught was the future Yamaha were also developing their V-Boost system for the V-Max. This system, effectively a twin-choke downdraught carb for bikes, required the airbox to move in front of the fuel tank and to sit directly above it. Yamaha’s engineers discounted V-Boost for the FZ, but adopted the downdraught idea to give more gas at higher speed to an engine that wanted to rev. Bike number 11 was adapted in 1983 to be the basis of a new roadster. Detuned to 100bhp for reliability. Yamaha were there.
9 It was the genesis of the ‘Genesis concept’ Yamaha’s Genesis concept defined sports bikes of the late 1980s but it wasn’t about just having five valve-heads or alloy beam frames.
Genesis was about designing the motorcycle as a whole – getting away from the traditional Japanese problems of too much power in not enough chassis. The FZ750’s engine and chassis design worked as one.
10 And the steel frame’s last stand. Suzuki’s GSX-R might have had an all-alloy cradle frame but it was still essentially the same design as your dad’s old Norton. Kawasaki had used a spine frame on the GPz, but the future was Yamaha. The FZ’s frame spars came out and around the engine. Still high, like a cradle, but it was the beginning of the beam frame. The next generation wore their frame spars lower and wider to give more room for bigger airboxes. And after the FZ, it was all alloy.
11 Within two years it was obsolete. Such was the pace of development at that time. Honda’s 1986 VFR750 had an alloy beam frame, and a V-four 16-valve engine that made almost as much power and better midrange. Kawasaki’s GPX750 made the same power from a 16-valve engine in 1987 and Bimota’s YB4 showed everyone the future of chassis design. The competition was learning fast. The FZ became the FZR1000 in 1987 – a proper race replica with an alloy beam frame plus suspension and brakes from another world.
12 But in racing, it was still good enough to get Eddie Lawson his first Daytona 200 victory in 1986. Lawson finished more than a minute ahead of Kevin Schwantz. It also won British Superstock in 1987. FZ750s filled four of the top five places and seven of the top 10 in British Superstock. Keith Huewen won the title by 35 points from Roger Hurst, also on an FZ.
13 Harris built the fairing lowers. By 1986, half fairings were for losers no matter how pretty your engine looked. Yamaha needed a full fairing and Yamaha UK approached Harris Performance to build some as a £300 option. By 1987, Yamaha
had redesigned the FZ as a fully faired machine.
14 It was the future of front suspension. Yamaha ignored the fashion for anti-dive front forks and instead talked of variable self-adjusting compression damping – essentially a valve in the front forks that controlled the oil flow depending on the rate of travel.
15 But not at the rear. The single shock fitted to the FZ had adjustable preload and rebound damping, but the preload was adjusted by a small chain, similar to the early RD350YPVS. And just like the RD, the chain would break after one winter’s use.
16 The oil light measures level, not pressure. Like most Yamahas up to the mid-1990s. So when the light comes on, chances are it just needs a top up, not a bottom end rebuild.
17 In seven years’ production there were only two official updates. The 1987 revamp got a full fairing, four-into-one exhaust, minor engine modifications to reduce friction and a milder exhaust cam. A new rear shock absorber and revised linkage to give more wheel travel, revised fork internals and solid brake discs. The 1991 revision brought new wheels including a 17in front, bigger discs and four-piston front brake calipers from the FZR1000.
18 Decent aftermarket exhausts are scarce. Motad’s race pipe added 10bhp if you also raised the front of the fuel tank half a centimetre. But was loud enough to deafen Lemmy. Motad don’t build noisy pipes for the road and the limited numbers they built for racing were very carefully controlled. But some of the handcrafted pipework did escape the paddock and (literally) caused headaches for both riders, villagers and coppers everywhere.
19 It had the longest bar-end weights we’d ever seen. No one knows why – the FZ engines aren’t especially vibey. But plonking your hands on an FZ’s bars was a very different feeling. Slim grips and a lot of metal sticking out. Thankfully the riding position was spot-on.
20 It revved to 11,000rpm, but was also a longer stroke engine than the GSX-R or VFR. Long stroke means better midrange but also high piston speeds and usually lower redlines. Thankfully, the FZ was built to last. The smaller intake valves were also 20 per cent lighter and that, coupled with the downdraught technology allowed the Yamaha to make more power throughout the rev range and hold onto it for longer. At 7500rpm, the FZ made 15bhp more than Suzuki’s GSX-R750.
21 And made more power than any of the 750s. Even by 1987, against Honda’s VFR and Kawasaki’s GPX, the FZ was still the most powerful (just) 750 with 90.6bhp at the wheel. The GPX made 90.5bhp, the VFR made 87.7bhp and a GSX-R made 88.3bhp.
22 It was the fastest accelerating 750 too. Despite weighing 29kg more than a GSX-R, the FZ’s flexibility and power advantage made it a tenth of a second quicker over the standing quarter mile. 11.3sec for the FZ, 11.4sec for the Suzuki.
23 And the fastest top speed. The Yamaha managed 148.7mph, compared to the GSX-R at 145.5mph, VFR at 143.1 and GPX750 at 146.9mph.
24 Valve clearances were 28,000 miles apart. Because the lighter valves were less stressed and less likely to go out of adjustment, the service intervals could be longer.
25 In 10 years time they will be expensive. FZ750s are cheap right now. Hacks at best, but many have been cruelly streetfightered or just left to rot. Unfair because this is a landmark motorcycle. The first of a new generation and possibly Yamaha’s greatest ever road going moment.
Make Model
FROM THE WEBSITE:http://www.motorcyclespecs.co.za/model/yamaha/yamaha_fz750
Yamaha FZ 750 Geneses
Year
1986
Engine
Liquid cooled, four stroke, transverse four cylinder, DOHC, 5 valves per cylinder.
Capacity
749
Bore x Stroke 68 x 51.6 mm
Compression Ratio 11.2:1
Induction
4X 34mm Mikuni carbs
Ignition / Starting
CDI / electric
Max Power
105 hp 74.4 kW @ 10500 rpm (rear tyre 94 hp @ 9400 rpm )
Max Torque
81.4 Nm @ 8000 rpm
Transmission / Drive
6 Speed / chain
Front Suspension
Telescopic forks non adjustable.
Rear Suspension
Monocross with single shock adjustable for preload.
Front Brakes
2x 270mm discs 2 piston calipers
Rear Brakes
Single 270mm disc 1 piston caliper
Front Tyre
120/80 V16
Rear Tyre
130/80 V18
Dry-Weight / Wet-Weight
209 kg / 222 kg
Fuel Capacity
22 Litres
Consumption average
38.3 mpg 16.3 km/lit
Braking 60 - 0 / 100 - 0
- / 35 m
Standing ¼ Mile
11.3 sec / 116.3 m
John Nutting fails to exercise his constitutional right to remain silent after crimes against the red line aboard Yamaha's FZ750...
The head honchos at Iwata will be the first to admit that Yamaha haven't had a very good decade, so far. Corporate enthusiasm tuned to beating the daylights out of Honda turned sour when it dawned on the Yam execs that Yamahas are not Hondas in the minds of punters. The name Honda is virtually synonymous with motorcycle in most parts of the world and Yamaha found to its cost that to attempt to break the mould is just a recipe for breaking the bank. In a word, Yamaha sales slumped.
The repercussions of the collapse echoed long after the replacement of the company President. Revised plans were initiated to put the company back on its feet; a degree of caution characterised the approach. British importers found that, despite the enthusiasm for the RD500LC and the FJ1100, the men from Iwata were sceptical of sales potential, so model allocations for Britain were low, reflecting the squeeze being applied at all levels, not least in the PR department. The result was that Yamaha caught a little bit of a cold in that sales of these two highly desired bikes didn't reach their full potential.
It's not a mistake the factory intends to repeat with the FZ750. Yamaha claim that the 5-valve in line four is to be a cornerstone of their range for the next ten years. A touch of cynicism might be acceptable here; after all, the bike trade has seen the pace of change accelerating by the second over the last two to three years, to the extent that to dwell on a new model for any length of time is to miss the impact of its successor.
But in an age where 'planned obsolescence' is translated into barnacled cam lobes and anaemic cam chains, Yamaha is keen to impress on us the longevity of this new engine, quoting oil-change intervals of 7,500 miles (!) and valve gear that'll only need the once over at 25,000 miles (!!) It all seems to good to be true, but if it is, we're on the way to the maintenance-free machine.
Like the Suzuki GSXR750, which we've yet to try out, the FZ750 makes a claimed lOObhp. That gives the hike a specific power of 133bhp per litre, putting it above Kawasaki's GPz900R's 125bhp/l, and it is only beaten by Honda's VF500F vee-four's 140bhp/litre.
Without the means of substantiating that claim on a dyno the only way of finding out if Yamaha were good as their word was to give the bike a good thrashing in Portugal.
Result was that it clocked 145mph at 10,800rpm in top gear on a deserted road south of Lisbon. By any reckoning that's pretty good for a 750 and it relates well to the 137mph top speeds accredited to the 90bhp 750's.
Now this top speed may be connected to the bike's remarkably slim profile. Long proponents of the idea that across-the-frame fours should be as narrow as possible, Yamaha has gone a step further with the FZ by exploiting water-cooling so that the pots are closer together and disposing of ignition components on the end of the crankshaft by using the end faces of the outer crank webs as part of the pick ups. Overall width of the motor is just 16.3 inches, less than the factory's own Japan-only air-cooled XJ400 four and about the same as Honda's vee-fours.
The speed may also be something to do with the neat fairing, claimed to offer a drag coefficient of just 0.34. It is certainly to do with power, and what's interesting is that it hasn't been attained by sacrificing flexibility. Though the FZ750 makes its best power over 7,000rpm, storming out of corners with the rear wheel drifting, it still pulls well from a walking pace in sixth.
This is where all the criticism of the complexity of five-valves-per-cylinder hits a block. Ten years ago we had 750cc racing engines putting out 90bhp if they were lucky, and only then with power bands a couple of thou wide valves. Valve springs need to be stronger to keep the cam followers on the cams without damage.
Four-valve layouts have gone a long way to raising the mechanical limits and improving the combustion chambers shapes which ideally should be a simple sphere. Honda first used four valves on its racers of the sixties to lighten the valve gear and raise the rev limits. But combustion was poor because of the awkwardly shaped piston crowns.
Yamaha claims to have tried to obtain the perfect combustion chamber with a seven valve arrangement that offered 20,000rpm limits. But, as you'd expect, fitting this number into a small combustion chamber proved too expensive for a production machine and eventually after trying six valves, five valves offered the best compromise.
The benefits are broad. By laying out the three inlet valves so that the middle one is out of line, and at a different angle from the cylinder axis, but still operated from the camshaft by a bucket follower like the other two, the combustion chamber shape needn't be complex. Indeed, Yamaha claims an 11.2 to 1 compression ratio which is remarkably high and shows that the combination of a slightly dished piston crown and centrally placed spark plug in a symmetrical chamber is the way to go.
Three small valves can flow more air than two and in the FZ's case they need less lift and opening timings to achieve it; that's the reason why the motor is more flexible than you'd expect. The three valves are individually lighter, so the point at which they start to float is higher up the rev range. Yamaha placed the red-line of the FZ at 1 l,000rpm with a rev limiter operating at 1 l,800rpm.
Because the valves are lighter, they need less strong valve springs so not only is the power absorbed by the valve gear lower, the camforms needn't be so radical. Wear is reduced as a result.
Straight, uninterrupted inlet ports have always been the goal for obtaining high power from four-strokes. Trouble is they're difficult to fit into bikes without getting in the way of the rider. But at the suggestion of the race team during the FZ's early development the engine was laid forward so that the air box was where the front of the fuel tank would have been. This meant that both the inlet ports would be straight and the spacious airbox got large helpings of cool air.
Yamaha's engineers say that the first prototype engine developed 130bhp at 13,000rpm, a not unlikely figure because they're claiming 330bhp at 13,000 for their two-litre vee-six car racing engine, and the production lump needed detuning for the road.
On the road, the FZ is smoother than most straight fours and as expected the hydraulic clutch and six speed box are slick, though at the expense of slack in the drivetrain at low speeds.
It's also very low with a sporting riding stance that tucks the rider behind the screen sufficiently well to keep his helmet out of the breeze. Steering is light and vice free despite the use of a 16-inch front wheel, a remarkably steep steering head angle of 64.5 degrees and short trail of 97mm. This is possible because, says Yamaha, pushing the engine-forward puts more weight onto the front wheel -almost 50 percent with the bike unladen.
For the scratchers, the news is that there's so much cornering clearance that they'll be in the gutter before anything hard drags despite the use of stickyish Dunlop Japanese tyres in fat 120/80V16and 130/80V18 sizes. The rear is an 18-incher so that racers can fit the more widely available slicks in this size.
Without doubt, Yamaha is hoping that this bike will form the basis of racers for the world endurance series and TT Formula events. With this in mind there's a tuning kit on the way that'll bring the power back to around 130bhp, making it more than competitive. In almost every respect, the bike's a detuned racer, but, like the RD500LC, the quality of the engine and running gear is such that it offers a refined package for the road.
Source Which Bike 1985.
I own one of these, I'm a demanding owner "- yet very satisfied that the above is the truth .