Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126040
A -SHAFTIE WITH A TWIST Spying on the XS7S0 Yamaha ..... - By Lane Campbe ll I-< ~ A routine .P R photo • assignment took on new dimensions with this first fragmentary glimpse of the Yamaha XS750 shaft-drive triple in teardown. (The occasion was the triumphant return of a six -man/six-bike test crew from a 6500 mile round trip with nothing worse than the odd crash and a blown fus e to mar the record.) What's unique about this seemingly over-engineered roadburner is the extra right-angle gear pair needed to fit a shaft to a transverse engine. This "middle gearbox" is a bolt-on; and - the man in charge of the ' wo rk crew admitted it would only take a cover plate and some seals to make it a .ch ain drive instead, I with the box removed. IImmm. When asked about a possible production racer in the works, the man only said, "We're.. still seeing what kind of output we can derive from it." On spec, the ou tpu t should be the re, else why the DOnC and valves that fill all the available headspace, worked with straight-forward inverted-cup followers? It's aU a bit too refined to be aimed . exclusively a t the fair ing-and-bags "elephant" trade. Couldn't ge t a shot' at a crank, but learned that nearly all engine bearings are p la in split shell automotive-type with high pressure lubrication. That goes for the cam bearings in their split pillow-blocks as well. All the gears apparently still ride on ball-and-roller carriage. Chassis is fairly state-of-the-art with dual discs front, calipers trailing; single disc rear; shaft drive and alloy rear bevel gear-case incorporated into the swingarm. The allo y wheels, of course, wiU soon. be d e rigeur ·for all high- zoot road bikes. Lots of solid-state electronics are integrated into the wiring harness to make every th in g buzz, whir, hoot, b link, click, whatever in passable imitation of Detroit. All kidding aside, the XS750's shakedown cruise and subsequent teardown seems to indicate a heavily overdesigned turnpike cruiser for which Yamaha mayor may not have other interesting plans. All depends on which way the Feds jump on emissions, now doesn't it? I'" -....- ..-._.. . . .. 32 l .'0. '0. '0. . ~ ~ Fea rle ss Yamaha Te st Team back from the wars_ (Top) Left side : Beauty of this bolt-on ge arcase (upper p hoto) is t hat you can picture a countershaft sp rocket in its p lace. Lightweight inverted cup fo llowers with hardface inse rt shi ms do the d uty on valves that just about f ill the avail able hole (lower photos) Right side: Diecas t four-main-bearing cases are almost pretty e nough for artwork (upper). Note that only one t ransm issio n shaft is in common plane wi t h crank. The other comes away with a separate carrier . A spur t ransfer gear (no t shown ) takes power to output. Overall , it's a bit sophisticared for the e lephant trade (lo we r photo), t hou gh it st ill has igniti o n po ints (three sets) instead of COl. Degree wheel is for shop use; d iaphragm-type CV fuel-m ixers and ca m chain drive could almost have been lifted from the 500 twin. .. . .. R '