Three Equals Four: 1979 Yamaha XS750F

In the mid-1970s, Yamaha’s fiasco with its 1973-1974 TX750 overhead cam twin had sent the company scrambling back to the drawing board to come up with something fresh. Next door neighbor and competitor Honda was selling every CB750 Four it could produce, and Yamaha desperately needed a hit in the 750cc category.

Eager to clean the egg on the face left by the TX, a nice-looking machine with an unfortunate propensity for blowing up crankshafts, Yamaha had to come up with something good to quash the rumors that it didn’t possess the know-how to build good 4-stroke engines. “They should stick to 2-strokes,” was the often-heard comment in bike circles, even though the double overhead cam, 4-valve-per-cylinder TX/XS500 received favorable reviews by the motorcycle press, and Yamaha’s faux Bonneville, the overhead cam XS650 twin introduced in 1970, continued to prove its robust design. But that wasn’t enough: Yamaha wanted a new 750, and it had to make a statement loud enough to silence the critics.

Enter the XS750

Released in Japan in early 1976 as the GX750, the new 750 packed a long list of new features, including a shaft-drive transverse engine, headlights that automatically turned on when the engine started and self-cancelling turn signals. Mechanically, the new bike was unlike any Yamaha before it, sporting a 3-cylinder, 64 horsepower, double overhead camshaft engine, a 5-speed transmission and shaft final drive.

In an attempt to minimize engine girth, the cam chain was placed at the end of the crankshaft, allowing the cylinders to cozy up and decreasing overall top end width. However, because the brushless alternator and the ignition points/starter clutch were placed at each end of the crank, the engine was a bit chunky at the waistline, measuring 20.5 inches from cover to cover, the same as Honda’s 750 four. Primary drive was via a Hy-Vo chain wrapped around an inward- instead of outward-facing clutch hub. A stout 4-point mounting bracket held the clutch in place and a rubber disk imbedded in the clutch cover helped dampen vibration and clutch noise.

A curvy 3-into-1, chromed exhaust system sprung out like a lighted-up theater marquee over the compact blacked out engine, emitting a lovely triple symphony thanks to the triple’s almost perfectly square 68mm x 68.6mm bore and stroke and 120-degree crank, resulting in smooth, relaxed operation.

The new 750 was praised for its café-ish looks, from the gorgeously sculpted fuel tank (the recess to clear the rear cam cover was a nice touch) to the short seat fairing. The double-cradle steel frame was contemporary, with dual down tubes looping under the engine, meeting the rear side tubes at the driveshaft pivot. Perhaps worried about engine loads and torque, Yamaha’s frame engineers employed a massive box-section center spar and ample bracing. There are three cross bars; one in front of the engine just below the exhaust, another at the back under the driveshaft, and yet another under the airbox. The engine had only three mounting points, one each side at the front and one under the transmission, with a long bolt sandwiching the cases. Although the engine was not a stressed member, Cycle World’s August 1976 review, referring to the engine’s lack of vibes, speculated that “Yamaha has found a way to rubber mount the Triple in a manner that prevents annoying low-rpm shake and yet holds down cruising-speed buzzing.” In fact only the handlebars — not the engine — were rubber mounted, but it was that smooth.

Welcome to America

The XS arrived stateside in late 1976 as a 1977 model, virtually the same as its Japanese home market sibling aside from some minor cosmetic changes including a slightly bigger tail cover and minor tuning mods. The first foreign market bikes were XS750C models, and by the time the bike got to the U.S. it was the XS750D. In January 1977, after fixing a second gear slipping problem and retuning the engine, Yamaha renamed it the XS750-2D.

According to Yamaha, retuning on the 2D was mostly down to fitting longer duration cams. In its April 1977 issue, Cycle magazine noted that “the inlet valve opens 4 degrees earlier (at 40 degrees BTDC) and closes 4 degrees later (at 64 degrees ABDC) than the D model, and the exhaust valve opens 4 degrees earlier (at 64 degrees BBDC) and closes 4 degrees later (at 40 degrees ATDC). Duration is up to 284 degrees, or 4 degrees longer than the [Kawasaki] KZ/Z-1 or [Suzuki] GS cams.” That was fairly racy for the time, but the bike didn’t break any records, running the quarter-mile in 13.69 seconds in Cycle World’s April 1977 test. By comparison, the earlier 750D ran the quarter in 13.992 seconds while the new 1977 Suzuki GS750 four turned in a time of 12.83 seconds.

While the original 3-into-1 exhaust gave the bike a sporty look, it paradoxically reduced right side ground clearance. The 2D’s new 3-into-2 system eliminated that problem, tucking the collector and crossover underneath the engine and using smaller diameter mufflers, with the left cylinder header feeding the left muffler and the center and right cylinders the right muffler.

The Mikuni BS34 carburetors remained the same, but were chastised by a few unlucky owners. They didn’t have any overflow plumbing, so if the vacuum-operated petcocks failed to close or the carburetor float valves failed to seat, gasoline would bubble up to the carb throats, filling up cylinders and flooding air boxes.

The Showa suspension garnered praise for being well sprung and dampened, front and rear. Fork spring preload could be adjusted by a press-and-twist mechanism fitted on the cap, with three levels of adjustment that could squeeze the spring almost an inch. Highway riding was class leading with 5.5 inches of fork travel. Small bumps were soaked up while larger ones were nicely managed by the progressive dampening. Rear shocks were OK for riding solo, but with only 2.5 inches of travel things could get dicey quickly on two-up hauls around twisty roads.

The E and F models

Most of the updates on the E and subsequent models were performance driven. The compression ratio was bumped from 8.5:1 to 9.5:1 and combustion chambers were reshaped for more efficient burning. The camshafts retained the same lift, but duration was once again increased to take advantage of the new reshaped and re-jetted Mikuni BS34 carburetors and larger airbox. Yamaha’s Transistor Controlled Ignition (TCI) was added, raising the redline from 7,500 to 9,000rpm. To take advantage of the extra kick in the seat, Yamaha lowered the secondary ratio to make the triple feel like a V8. The annoying gap between first and second gears got much less annoying, and fifth gear roll-ons became smile-inducing: You could forget about the shift lever when touring — just twist the throttle and enjoy the rush between corners, the bike returning around 45mpg on premium gas.

There were some niggles, with bike magazine testers complaining that the carburetors were over-responsive. Testing the 1978 E model in its October 1977 issue, Cycle Guide said: “While the single-pull vacuum operated carburetor slides require only a light hand on the throttle for touring (which is good), they’re too light and touchy for around town. That, combined with lash in the two driveline shock absorbers, and just the slightest bump in the pavement will send the rider and the chassis lurching to and fro.” 1978 also saw the introduction of the XS750SE Special, a factory “custom” featuring a teardrop tank and a stepped seat.

The F model, the last of the 750s, arrived in 1979. Mechanically unchanged, the engine was now left au naturel, with clear-coated engine cases, a bare aluminum top end and a few bits painted silver and/or black. Color options were Vintage Burgundy and Black Gold, the color of our feature bike.

John Chaves’ 1979 XS750

Having owned a 1978 XS750E back in the early 1980s and wanting another, John Chaves decided he wanted to find an XS750 to restore. He had finished a restoration of a 1975 XS650, and it was time to start something new. After an incredible stroke of luck, he found our feature 1979 F model, with very low miles (see sidebar).

According to the seller, the bike had been parked in a barn in Long Island, New York, for more than 30 years, but it was only when the delivery truck pulled into John’s driveway in Lutz, Florida, that John started to believe the seller’s claim. Rusty and dirty, she was yet whole, with nothing aside from a rear turn signal missing. Popping the seat up (with the original key) revealed an unmolested OEM toolkit and the owner’s manual stuck in the little utility box tucked under the tail cover. The wiring was untouched, with assembly tags still attached to it. After connecting a remote fuel tank and a good battery, the bike fired right up, spitting and sputtering, and leaking fuel through the airbox. “Who are you to wake me up?” John says he remembers thinking.

After stripping the bike down, John sent the frame off for powder coating. With every possible opening sealed the engine was soda blasted and the crankcases painted by Kevin Bates at Tribby’s Auto & Marine in Largo, Florida. The cylinders were left bare aluminum. The original 00H9-Black Gold paint was still available from Color Rite, and Reproduction Decals provided the correct decal kit. The paint job was delegated to Morrel Roberts at Moe Colors, who did a flawless, museum-quality job.

The brake hydraulics were all rebuilt and the fork seals replaced. Most of the chrome parts — exhaust headers, front fender, etc. — needed re-plating, but the mufflers had only superficial rust, nicely removed following a two-day bath in Metal Rescue.

The engine was mostly left alone. The valve and side covers were sent out to Erik Hausch in St. Petersburg, Florida, for polishing and the oil pan was dropped for inspection. “I didn’t want to take any chances,” John says, adding, “You never know what’s in there until you look.” Thankfully, all was clean and in order.

John has put about 500 miles on the XS since it was reassembled. “I’d like to keep the miles down, but it’s so dreamy and amazing to ride, I can’t resist,” John says. “I have to keep reminding myself that the engine still needs to be broken in!” Most of the new miles were earned during last year’s XS Southeast Rally, held yearly in the Blue Ridge Mountains. “Just leave it in fifth gear and roll the throttle on and off and the big 750 dances around the corners as gracefully as the hippos in Disney’s Fantasia,” John adds.

There are other bikes in John’s garage, but none of them have the ability to transport him back to the past like the 750 does. “I like the new stuff, too,” John says, pointing to a late model Yamaha FZ-09 parked next to the XS. “But there’s something about the XS that got lost on the way to lighter, faster motorcycles, and she always reminds me what that is. The long-stroke, 120-degree triple produces a very unique, deep bass sound, while modern triples wail like a four, and the long wheelbase and low center of gravity allow the XS to remain poised on the Interstate. She’s a true highway star.” MC

Found: Time warp 1979 Yamaha XS750

It’s lunchtime and the phone rings. It’s my buddy Mike telling me to look in my email. “Quick!” he says. Sensing the urgency in his voice, I dropped what I was doing, logged in and saw a message from him titled “You gotta see this!” with a link to a New York state Craigslist posting that read: “1979 Yamaha 750. Parked for over 30 years. Runs but needs work. 291 miles.” I almost fell off my chair! 291 miles! “I bet the seller meant to say 29,000 miles,” I started to think, but I picked up the phone and called. A young man answered and confirmed what the ad said. Sensing my wariness, he asked, “Would you like to talk with my dad?” Mr. Seller Senior came to the phone and told me the bike’s story.

In the summer of 1979, one of his neighbors in Long Island, New York, bought the bike and a boat. As soon as his new purchases arrived the neighbor’s wife said, “Boat OK, but the motorcycle’s gotta go!” Unwilling to get rid of his shiny new black diamond, he asked Mr. Seller Senior to hide the bike in his barn. Understanding the plight of his fellow man and trusty neighbor, he agreed. Every chance he had, Mr. Owner would sneak out, two houses down and across the street, to fire up his XS and do a few loops outside town, cherishing every ride.

A short time after the purchase, Mr. Owner got a job transfer and left the bike behind. Remember that in the eyes of the wife, that bike was long gone. The XS spent the next 20 years in the same spot in the barn, leaning against the wall, buried under a pile of hay, farm equipment and junk. One shiny day, Mr. Seller got a letter with the motorcycle title. “Thanks for keeping the bike and the secret for all these years. She’s yours more than she’s mine,” read the note included in the letter. After a few unsuccessful attempts to get it running, Mr. Seller Senior placed the ad on Craigslist that my friend Mike saw. One week later, the bike was in my garage. — John Chaves