Yamaha XS750 SF Special – Vetter Quicksilver – Updated January 2012

26 Feb 2015 | Author: | Comments Off on Yamaha XS750 SF Special – Vetter Quicksilver – Updated January 2012
Yamaha XS 750

Déjà Vu

1979 Yamaha XS750 Special Combining a Yamaha XS750SF Triple with a Vetter Quicksilver fairing created a synergistic combination back in 1980. Recreating that combination more than 30 years later evokes a little vintage Déjà Vu.

C oinciding with the peak of the music industry’s disco craze, the Yamaha XS750D standard first arrived in late 1976. The motor press at the time commended Yamaha’s new 750 Triple as being a competent and attractive motorcycle, but found it not too exciting – a little like taking your sister to the movies. Certainly OK, but better options usually come to mind.

All that changed for 1978 with an increased emphasis on performance and perhaps more importantly, the introduction of the Special.

The engineers at Yamaha had been following bike trends here in the U.S. for quite some time, eventually borrowing a few of the design elements from the Harley crowd. Borrowing design from other manufacturers wasn’t new then and it certainly isn’t new now, but the XS750 Specials began the bad boy biker trend at Yamaha that continues to this day.

Cruiser handlebars, a teardrop fuel tank, stepped seat, bobbed rear fender, short mufflers and a leading-axle front fork completed the largely cosmetic transformation. Just the thing for looking cool while cruising the boulevard, we were told.

My street bike experience began in 1964 with a string of small to medium-sized Suzuki 2-stroke street bikes, a Honda 4-stroke twin and even a couple of Harleys, but I found myself without a bike in late 1979. All of the previous machines taught me way more than I wanted to know about points ignition and chain maintenance. I knew that my next bike must include electronic ignition and shaft drive, look great and be fun to ride – with enough power and handling to do anything I needed it to do.

My search ended in early 1980 at a local Yamaha dealer’s showroom with a pulse-quickening carmine red 1979 Yamaha XS750 Special.

My first XS was put to work as a commuter in the spring of 1980 – about 55-miles roundtrip 5 days a week and as an occasional weekend warrior. The somewhat short riding season here in Montana can be stretched to about 5 full months, with the early and late season requiring some cold and dark morning commutes. The cold, the rain and the bugs soon became wearing. I rode with a full-face helmet, good gloves, boots and a selection of jackets, but they weren’t enough.

I needed more protection from the elements.

Back in the day, Craig Vetter was known worldwide for his great looking and highly functional aftermarket fairings that, with a bike-specific mount, would fit nearly all of the then currently produced motorcycles – including my 1979 Yamaha XS750 Special. While the larger Windjammer model became the most popular Vetter fairing, I wanted a smaller and lighter fairing that didn’t detract from sporting nature of the Yamaha, but still provided enough wind, rain and bug protection to help make commuting a more pleasant experience.

Luckily, Vetter also produced the smaller and more versatile Quicksilver shown here, which added just 12 pounds to the bike. In addition, the combination looked great and made the bike a lot more livable on a day to day basis.

Nearly every biker I’ve met through the years has expressed at least some regret for selling a motorcycle they once owned. I’m no exception. I regrettably sold that red XS750 after 8 years and more than 27,000 miles of ownership. While I owned a series of off-road bikes from the late 70’s to present, I had been without a street bike from late 1988 through late 2008 – some 20 years.

I had a lot of good times on that first XS750, and in late 2008 I began wondering whether any XS750 Specials were still on the road. So, an Internet search began. Like the prodigal son, I was coming home.

Meet Déjà. The black 1979 XS750 Special appearing here was purchased in January 2009 from a Yamaha dealer in South Dakota, which was then shipped to my home in Montana. This bike was chosen because it was an unmodified original and appeared to be in decent condition.

Being a realist, I knew that any unrestored 30-year old bike would need some TLC, though I expected the bike to be fully functional and without any significant mechanical problems. Buying a motorcycle via long-distance can be somewhat risky, but working with an established power-sports dealer helped, as did the selection of hi-res digital photos and a video clip provided by the dealer.

Soon after acquiring Déjà and returning it to stock, I began looking for another Vetter Quicksilver. I then learned that Vetter had gotten out of the business in the mid-1980s, which meant buying a new fairing wasn’t likely. However, eBay came to the rescue! A Wisconsin motorcycle dealer was advertising an NOS (New Old Stock) Vetter Quicksilver on eBay for about the same price I paid in 1980.

As it turned out, Milwaukee Cycle had about a dozen NOS Quicksilvers on hand as well as the exact Yamaha XS750 Special fairing frame mount I needed.

In addition to adding a Quicksilver fairing to both my first and second XS, I also installed new sport-oriented handlebars. Instead of the bolt-upright sitting position the factory rubber-mounted cruiser bars forced the rider into, the new shorter/flatter sport bars (still rubber-mounted) allow the rider to sit in a more relaxed, slightly leaned-forward position, which provide for all-day riding comfort.

Period magazine reviews suggested that the Specials weren’t ideally suited for carving canyons. I know that replacing the ungainly factory cruiser handlebars with a set that is more sport-oriented will transform riding comfort, handling and rider confidence.

It’s been said that you can never go back. While I don’t have to commute now, I very much enjoy riding my new-to-me XS every chance I get. At the time this was written, Déjà has delivered another 6,000 trouble-free miles, and the XS Special has proven to be just as reliable and just as much fun as I remember.

The 1979 Yamaha XS750 Special is a great looking and performing vintage motorcycle. The addition of the Vetter Quicksilver and sport handlebars complete the package, and now more than 22 years after selling my first XS, I can’t help feeling that sense of déjà vu whenever we’re on the road together.

Inspired by the Brits, Yamaha’s foray into the 4-stroke street fighter realm began with the 1970 XS-1, a 650cc vertical twin, which was the largest motorcycle engine Yamaha had built to date. It was a good looking and reliable engine, and it enabled Yamaha to remain competitive in a very competitive market. Testifying to its goodness, the 650 twin remained available here in the U.S. for a remarkable 13 model years.

While Honda and Kawasaki had gone to 4-cylinder engines for their 4-stroke 750s in the late 1960’s/early to mid 70s, Yamaha’s first 4-stroke 750 became available in 1973/74 as the ill-fated TX750 twin. To recover from the TX, Yamaha needed a clean slate engine, and that’s what they delivered in 1976 as the first XS750D – a 3-cylinder 4-stroke 750. At the time, Cycle World magazine called it a bargain BMW” and declared it one of the world’s 10 best motorcycles.

Triples were not new to motorcycling in the mid-1970s. Both Kawasaki and Suzuki were successful throughout this period with their 3-cylinder 2-strokes. I owned and rode a Suzuki GT380 Triple for more than 40,000 miles through the mid-1970s, and like most Suzuki fans, longed for their big GT750, a powerful water-cooled 2-stoke triple. As good as 2-strokes were, street bike manufacturers were moving toward the 4-stroke. Like Japan, the British also found value in the Triple.

Both BSA and the closely-related Triumph brands produced 750cc 4-stroke Triples. The last Rocket IIIs rolled out of the BSA factory in 1972, while the Triumph Trident T150 was replaced by the short-lived T160 in 1974 (with electric start, forward sloping engine, front and rear discs). By late 1976, the Yamaha XS Triple was alone in the 3-cylinder 4-stroke 750cc market.

Yamaha added amenities to the bike that further set it apart from its 4-cylinder 750cc competition, like powerful triple-disc brakes, shaft drive and a stirring exhaust note that only a 120-degree Triple could produce.

Hampered by points ignition, a low 8.5:1 compression and mild cams, the original XS750 performed well-enough, but once the newness had worn off, the mild performance became passé. All that changed for the 1978 model year, when the engine received a number of significant improvements, which included an increase in compression to 9.5:1, higher lift cams with altered timing, electronic ignition, lower overall gearing and the redline raised from 7500-rpm to 9000.

These upgrades transformed the original Yamaha XS750 Triple from a mild-mannered Clark Kent into a genuine superbike (by 1978 standards). Due to minor changes made to the engine in later years to address EPA emissions rule changes, the 1978 XS750 became the best performing Triple.

The 1978 model-year also saw the introduction of the Special, which retained the best features of the standard model, but added stylistic mods loosely borrowed from the Harley Sportster. Cruiser handlebars, a teardrop fuel tank, stepped seat, bobbed rear fender, short mufflers and a leading-axle front fork were mostly cosmetic. While the cruiser handlebars negatively affected handling, on balance, the remaining modifications didn’t.

The XS750 models were produced from 1976 through the 1979 model year, with an estimated 150,000 total production.

For 1980, the XS got a bump in displacement to 850cc, an oil cooler was included, and minor stylistic mods were added to the standard models to give them a fresh look. The Specials received even more cosmetic upgrades, getting a swoopier seat and fatter rear tire. One available color scheme became the Midnight Special. At least to my eyes, the MS was perhaps the most attractive of the 850s, having a shiny black monochrome appearance with gold accents.

The engine, exhaust system, front forks and fenders were all black. Gold was used on the wheels, seat grab bar and smaller detail components that had been chromed on other models.

A 6 model-year run, ending in 1981, marked the end of the Yamaha Triples. Yamaha moved on to 4-cylinder engines with the shaft-drive XJ series, and the XS750/850 Triple faded from the press. Today, the Yamaha Triples remain in the hearts and minds of many vintage Yamaha enthusiasts simply because they work so well.

They are Special.

Things to watch:

1- These bikes came from the factory with a pair of vacuum-operated fuel petcocks. While I’ve yet to experience a problem with them on either my first or second Special, they have been known to develop a leak that allows fuel to either flow to the carburetors while the engine is off, which can cause a flooded engine and/or contaminate the engine oil if the float needle in one or more of the carburetors becomes worn, or fuel can back-flow through the vacuum hoses and run directly into the intake tracts of engine.

This sort of failure also contaminates the engine oil with gasoline. Running the engine with contaminated engine oil usually wipes out the crankshaft bearings. If your vacuum operated petcocks appear to be functioning normally, a quick check of the engine oil level, through the convenient sight glass in the right-side engine case, before every ride will reveal any problem with the oil level.

Some XS owners have replaced the vacuum operated petcocks with a manual variety. While this could end the possibility of a petcock failure that results in engine oil contamination, it does burden the rider with yet another easy-to-forget task, and constant turning of the petcocks will wear the various petcock seals, requiring occasional routine maintenance. Vacuum petcock rebuilt kits are currently available.

2- The transmission layshaft is held in position with a bolt and thick heavy washer on the right end of the shaft. The layshaft bolt has been known to fail, which then allows some lateral movement of the layshaft and associated gears. While this problem usually doesn’t result in more serious damage, you may find that 2nd gear won’t engage or won’t stay in gear.

Some blame wear in the gear train or the shift drum for this problem, and recommend changing the location of various shims to compensate. I believe the large and heavy layshaft washer acts as a flywheel, which fatigues the bolt over time, eventually resulting in bolt failure. Aggressive powershifting, abuse or otherwise rough handling of the transmission over a long period of time may be the root cause of this problem.

Profiling the heavy washer to reduce its mass may help – thick at the center and thinner toward the outer edge. Neither of my Specials has experienced this problem. I’m an easy shifter.

3- The Yamaha XS750 Specials were originally equipped with vented wet-cell 12-volt batteries. Too many of these bikes have been ruined through the years because of the destructive effects of acid corrosion – starting with the battery box, the electrical center and on down to the frame and swingarm. New AGM (Absorbed Glass Mat) batteries are now standard in most new bikes, and they are also available for most vintage and classic motorcycles.

AGM batteries are vastly superior to the old batteries in that they hold a charge several times longer than wet acid batteries during periods of inactivity and as a result last longer, and they are non-vented so they cannot leak in any position. Because of acid corrosion, Déjà’s battery box needed to be media-blasted and repainted soon after I got the bike. Luckily, there was no additional damage.

Déjà now has an AGM battery.

4- Over a long period of time, these engines can develop a slow oozing oil leak somewhere around the perimeter of the cylinder base gasket and/or head gasket. Many of these leaks can be dealt with by simply loosening and re-torquing the cylinder head bolts/nuts. Air-cooled engines experience countless thermal cycles over time, which tend to relax the clamping force applied by the head fasteners.

A simple re-torque according to either the Haynes or Clymer shop manuals is easy and won’t cost you anything but your time.

5- It’s become popular to replace the factory airbox with a set of three slip-on KN type air filters. Some owners do this because their original airbox had become mishapen or damaged over time, and some airboxes are replaced because the owners believe aftermarket air filters will improve performance. Don’t do it.

These engines are akin to an elaborate air pump. Maintaining intake air velocity is one way to improve performance, and individual air filters make no provision for maintaining the velocity of the intake air. The chambers found inside the factory airbox, on the other hand, were designed and tuned to maintain intake air velocity.

The airbox was also designed to reduce the intake air noise that can be annoying when running individual air filters. Installing a set of individual air filters requires a re-jet of the carburetors to compensate for the difference in airflow. Perfect air/fuel ratios are almost impossible to obtain when running individual air filters because air pressure immediately behind the cylinders varies with road speed.

The factory airbox pulls air from an area of the bike that is much less affected. Your bike will run better, will be quieter, and will produce better fuel economy and more power when running the factory airbox. If your factory airbox isn’t repairable, a replacement can be found on eBay.

I used a heat gun and gloved hands to reshape the ill-fitting removable cover on my airbox – to return it to its original form.

Press Reports:

All that work with compression, valve timing, exhaust systems, carburetion and gearing has transformed the XS750 from the modestly-performing machine we tested in August 1976 (which recorded a best standing-start quarter-mile run of 13.94 seconds at 93.9 mph) into a genuine, fire-breathing superbike (which laid down a best run of 12.88 seconds at 102.4). The Yamaha is quicker than any current 750 and even quicker than most 1000cc machines. Cycle Guide, October 1977

A unique engine configuration isn’t worth much if the powerplant doesn’t perform, but the Yamaha is at the very top of its class in useful engine performance. Cycle Guide, August 1978

It turns out the Specials have been enormously successful. Nearly half of the 750 Yamahas sold are Specials. Cycle World, May 1979

Specifications – 1979 Yamaha XS750SF Special:

Yamaha XS 750

Engine type – Air-cooled four-stroke, vertical transverse Triple

Valve arrangement – 2 valves per cyl, chain-driven double-overhead camshafts, shim adjustment

Bore stroke – 68 mm x 68.6 mm

Displacement – 747.3 cc

Compression ratio – 9.2:1

Claimed horsepower – 68 bhp @ 8000-rpm

Claimed torque – 47 lb-ft @ 6500-rpm

Ignition – Transistor-controlled electronic ignition

Carburetion – Three 34mm Mikuni Constant Velocity

Air filter -Dry foam element

Lubrication – Wet sump, 3.7 qt (3.5 L) capacity, 42-psi pressure-fed plain main rod bearings

Primary drive – Hy-Vo chain 1.67:1 ratio

Transmission – 5-speed, 5.71:1 overall gear ratio in 5th

Rear tire – 4.00H18

Wheels – 7-spoke tubeless cast aluminum

Frame – Tubular and pressed mild steel, double cradle front downtubes

Rake/Trail – 26.5 degrees/4.29 in (105 mm)

Wheelbase – 59.5 in (151.1 cm)

Weight – 521 lb (236.3 kg) dry (546 lb with oil and – tank fuel)

Gross vehicle weight rating – 980 lb (444.5 kg), 459 lb (208.6 kg) load capacity

Seat height – 32.3 in (820.4 mm)

Instrumentation – Speedometer, odometer, resettable tripmeter, tachometer

Warning lamps – High beam, Neutral, Oil Pressure Warning, Turn Indicator, Brake lamp fault, Tail lamp fault, Head Lamp fault

Fuel tank – Steel 4.9 gal (18.7 L), including 0.6 gal (2.3 L) reserve

Petcock(s) – Vacuum Operated Pair

Fuel consumption – 40-50 mpg (17-22.5 km/L)

Range – 172-228 miles (277-367 km) plus 24-32 miles (39-51 km) reserve

Performance – 12.99 to 13.33 sec @ 101-102 mph –mile and

120 mph calculated top speed

Stopping distance – 37 ft. (11.3 m) from 30 mph, 138 ft. (42.1 m) from 60 mph

Yamaha XS 750
Yamaha XS 750
Yamaha XS 750
Yamaha XS 750

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