Cycle News - Archive Issues - 1980's

BMW opted forthe simplicity afforded by a two-va lve combustion chamber. Intake valve is 34mm. exhaust is 28mm. experimented with th ese modern front suspension features, and, unlike other manufacturers, found th em to be unneces sary. A curious detail is that th e front brake h ydraulic system is routed through the steering stem; should different handlebars be fitted to the KI 00, only the length of hose between the master cylinder and the steering stem need be replaced. O n the other hand, this means that greasing the steering head bearings involves draining and bleeding the front brakes. For instrumentation, the KIOO sports traditional analog (dial ) gauges for the speedo an d tach - thoug h both are electronica lly triggered. Liquid crystal displays are provided fo r the clock and gear position indicator. Warning lights are used to m on itor engine temperature, battery chargi ng a n d oil pressu re. O th er h andy lights signal wh en th e choke is engaged, and wh ether the brake ligh t is burned o u t. Not so handy a re the fue l warning lights: a brigh t yell ow ligh t to indicate seven liters remain- ing, a nd a bright red one when th e tank is down to four liters. Ar night, these lights are nearl y blinding, ca us ing a real distrarion from th e road. Word is that the 1986 model KIOO will have an LCD gauge for th e fuel level. In the meantime, several resourceful owners have wired up a rheostat to dim the fuel lights for nighttime riding. BMW has always been fond of strange handlebar switches. In th e 1970s, not onl y were the sw itches 10ca red in unusual posit ions: they wert' Iestooned with cryptic vinternational " markings (m ea n i n g you couldn't figure them out .. . regardless of the la nguage you spoke). In 1979 that practice was abandoned, and the control switches were changed to confo rm to those found on other motorcycles. Wi th the introduction of the KIOO th ey're back at it again - this time wi th switches designe d by th e a u to motive studies team from the Tech nical Institu te of Aac hen, West Ge rmany . T he right turn signa l is a BMW K100 Engine type • •.• •• Water-cooled DOHC four-stroke inline-four Bore x stroke . . . .•.. 67x70mm Displacement . . •• • • • • • • 987cc Compression retio . •.. . . 10.2 :1 Carburetion . ...• Electronic fuel injection Horsepo_r . • __. ••• 88.5 bhp @ 8000 rpm Torque • . .. . . ... 63.7 Ibs.-ft. @ 6000 rpm Valves per cylinder • • • . . •• • . , 2 Inta ke valve size . . ••• • •• 34mm Exhaust velve size 28mm Intake lift •..•..• . ..• . • 9 .2mm Exhaust lift 9.2mm Incl uded valve angle . .• . . .• 38° Intake velva timing. . . .. 5 ° _27° Exhaust valve timing ... 28°_5° (measuring pt.) • • . . . • • • . . 3mm Ignition ... .. . . . . . • . . Electronic Lubrication . . .. •• . . . . Wet sump Redline .. . . .. . . . 8500 rpm rpm @ 60 mph 3800 rpm Gear ratios 1:1 Primary Final 2 .91 :1 5th 1 .67:1 4th . •. .... . . . .......• 1.88:1 3rd .. .. .. . .. . .. .. .. •. 2.30:1 2nd 2 .96:1 1st . . . . ... . . •.• •. •. •. 4 .50:1 24 Calculated speed in gears at redline 5th 131.26 mph 4th 116.36 mph 3rd 95.1 5 mph 2nd 73.90 mph 1st 48.6 1 mph Frame Mild steel backbone. engine stressed·membar Rake • • . . • . . . . • . . . . • . • . . . 27° Treil. 3 .97 in. Front suspension Telescopic forks Fork tube diameter . • • • 41 .4m m Front wheel travel . . • . . . . 7 .3 in . Rear suspension Single· shock swingarm Rear wheel travel . .•••.• 4 .3 in . Front brakes . . (2) 11 .2-in . discs Rear brake 11 .2 -in. disc Front wheel • . . . • . . . . . 2.50x18 Rear wheel .•. •. •.. . . . 2 .75x17 Front t ire . . . . ...• . ·10 0 / 90 -18 Rear tire • .• . . . . . . . 130/90-17 Dry weight 474 Ibs. 59.7 in. Wheelbase Fuel capacity . . • . . . . .. . 5.8 gal . Ground clearence 6 .9 in . Seat height 31.9 in . GVWR 992 Ibs. Colors . .... • • • .. . . . Red. Silver RetlIiI Price $5995 T h an k s to the skinny double-rail o il control ring. the K100 can smoke when f irst started . Piston is flat-topped. with cut-outs for valve clearance. push button on th e right handlebar, with the left signal activated by another button on the left handlebar. Cancelling the signals is achieved by lifting the right thumb, and honking the horn by lifting the left thumb. These controls take som e getting used to, to sa y th e least. Liv ing with a K 1 00 BMWs have long been exempt from direct comparisons with other motorcycles. Everybody knows the old Boxer twins were down on power, had suspensio ns a nd ha ndling that was decidedly behind th e times. a nd that th e bikes bristled with curious engineering q uirks left over from the O ld Da ys. To be sure, the old Boxers still enjoy a loyal fo llowing; riders who love the machines a t face val ue , and are will ing to accept their peculiarities an d sh ortco mi ngs. Bu t th e da ys of patron izing exc uses are o ver. While th e Box er wa s a blatant hold-o ver from the p a st, the introduction of the K I00 is a co mmitment to the future . BM W has invested seven years of R &D work, and over $200 million putting the Kloo into production. The buck stops here: the KIOO is a contemporary motorcycle, and demands to be j udged by contemporary standards. Quality and finish of the new machine a re well up to BMW's legendary standards. Welds are clean and precise. All nuts, bolts and fasteners are lavish ly plated, and didn't show the slightest hint of corrosion in the course of our eigh t month, 8,000 mile test. In fact. at one point the Cycle News test garage was full. and the KI 00 spent about two months parked in an editor's backyard. After that exposure, a thorough washi ng revealed that nothing had corroded or det eriorated in any wa y. Even more impressive is that the aluminum surfaces of the engine, transmission and swingarm aren ' t covered with the plastic coating found on most motorcycles. In spite of months of neglect, these bare metal surfaces retained their brand-new appearance; looking li ke they'd just left the fo u ndry. Throw a leg over the seat, dial on the choke. click on the igni tion an d the KIOO will stan instantly - soon settling down to a smooth idle.' The choke is necessary only for stone-cold starts, and can be dialed off as soon as the engine is running - a testimony to the effectiveness of the fuel injec- tion computer. However, if th e KIOO was parked on its sidestand, th e rider will soon be -en gu lfed in a cloud of blue oil smoke. Since the engine is horizontally oriented. when the bike is on the sidestand th e cylinders are actually pointed downh ill. Over a period of time. oil drains down th e cylinder walls , leaks past the rings. and pools in the combustion chamber. The basic ring design may be at fault; the onepiece oil control rings on the K100 pistons are skinny and weak when compared to the th ree-piece oil control ri ngs in other motorcycle engines. BMW claims that this problem was restricted to on ly the firs t few production Kl OO (our test bi ke was fra me s numberfivel) . .. but a ll KI O Oown ers are famil iar wit h t his smoking ten denc:y. While we' re on the to p ic o f p istons, there's anothe r in teresti ng con sidera tion to th e KIOO design . Wi th the horizon tall y-oriented engine. the KI OO powerp la nt holds the prom ise of one o f the easiest motorcycles to service. 'The crankshaft, bea ri ngs, rods and p istons ca n a ll be remo ved /repaired/serviced/rep laced while th e engine is mo u nted i n the frame. Except . . . the cyli nder walls, which are cast as part of the engine block, and are treated with the Sca nimet coating. As a result. the cylinders can't be overbored, honed. or serviced in any way. If one of the cylinder walls is damaged - a ring cracks. wrist pin or circlip comes loose, a valve h ead breaks off, a screw is digested through the intake tract - th e entire engine block must be replaced. Once warmed up and underway, the Kloo engine proves torquey (for a n inline engine), tractable a nd has a very wide powerband. Surprisingly, the KI O br.u es; with the same kind Ovi of "tingly" high-frequency vibration that BMW loya lists used to associate with Japanese motorcycles. Thevi bra "tion is present throughout the po werband. diminishing only slightly at the upper revs . Checking wi th several local BMW dealers, apparently this vibration ca n be minimized through carefu l tun ing of the fuel injection system. Early KlOOs had a problem with excessive (close to intolerable) vibration at the foot pegs, which can be improved with a new set of retrofit rubber footpeg bushings. Currently, the RS and R T versions of the KIOO empioy rubber front engine mounts to cushion

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