fork-dampening-&-springing-175-199m-1275

( ) ·’ BMW :.Jotorrad GmbH ;Service Ett/cb/fm Service-nI ·formation ~ 60/5 ~ ~ 90 S motorcycles ‘l’e chni ca 1 :•’Iunich, Dec 1 7~ 11 7 5 ( 1 :J 9 ~-1) e ——–···—·—···-·—-“-“-· ~0-;_;.p——J.;±———————- Subject: Front forks – damping and spri~ging Dampins; ~o prevent the fro~t forks from compressing too far or bottoming over undulating surfaces, a suspension damper with a harde~ compression phase has been developed. The uprated compression phase is particularly suitable for machines with the twin disc brake which are norraally riaten in an ent~usiastic manner. The compression phase damping action has c)een modified by omitting one lateral passage at tne base of the damper tube, thus restrictine the flow of the hydraulic fluid still further. The new damper tube Part number 31 42 1 234 474 has been introduced recently for all motorcycles equipped at the Berlin factory with twin disc brakes. The modification came into force as follows: R 90 VC ‘ us from frame number 498 0520 cl TIC. as special equiriment Ref. number 511. 2 as follows: R 60/6 us from frame number 492 0637 R 75/6 us ii II II 494 061+1 R 90/G us 11 II ” 496 7803 The modified damner tube can be installed subsequently on all /6 motorcycles so far produced~ without any further modifications being necessary. In order to offer interested riders the ‘harde.!.· ! -:oi,;oression rat~ at reasonable cost, a narrower-bore damper jet tfloating, see drawine on page 4) has been released: Part number 31 42 1 234 506 Identification: peripheral groove -2- I Kennlnis genommen – Pris connaissance – Noted – Tornado nota – Preso conoscenza : Ablage – Archives – File – Archivo i Belriebsle, lung : Werkslall KD-Arina~me Gewanrl. ·Sachb. ! Te,lediensl i Belriebsle,rung Werkstan ! Dirl3’ct1on : Aiel,er ;::;e-:em1,::”‘:I: -t,enteie lnso_ecteur garan11e i Service pu:l’Cesd etachees : Direction : Alelier ;,_ -· — . S.I. 1/75 (199 M) e – 2 – This also stiffens the tension phase of the dampers, but provides the desired effect without installation of the new damper tube. Warning Install the narrower-bore damper jets only in the threaded rings at the lower ends of the fixed fork tubes. ::ever install the narrower- bore jet as the spring-loaded valve plate on the damper piston (lower spring mounting), as this would severely increase the tension phase rating. If a motorcycle is normally ridden extremely nard, the narrow bore jet together with the new damper tube may offer improved handling and ride, since the combination of both modified parts will stiffen the compression phase still further. By way of enlargement on our Service Information 1/74(117 ~) issued in ~ay 1974, we quote again below the approved makes and { grades of shock absorber oil: Manufacturer Aral BP Castrol Castrol Shell Shell Oil grade 1010 Aero Hydraulic 1 DB Hydraulic Fluid Shock Absorber 1-313 Aero Fluid 4 4001 Shock Absorber Oil Oil content of each fork tube: Springing Initial filling Oil chan:,;e 280 cm3 265 cm3 In Service Information 4/72 (053 ~) dated Dec ’72,we gave details of front fork sprinzs developed for the /5 models. On /6 motorcycles, only the two stiffest (hic~es~-rate) vcrsio~s are installed. o~ prin•g 1 Used on Sprin 6 2 • , Used on ?ar’c number Length Wire dia. R ?OS Part number LienGt~1 ·~siire dia . 31 42 1 567 mm 4 mm 231 358 fro~ start of production 31 42 1 232 017 543 mn t1. 25 nm Specified if machine is equinped with a front enclosure, e.g. the SMW FULL PAIRING (not the BMW Cockpit) ( l -3- ( S.I. 1/75 (199 M) e – 3 – Reminder: As you will be aware, our full fairing is not approved for the R 90 S. These springs are also recom~1ended for C0~•1?C:TITIO’J purposes, in combination with tl1e hardest available Jamper compression rate (new damper tube and narrower jet). Our objective in supplyinc all our n1otorcycles with specific suspension rates and .c;ettine;s rather than ot!1ers is to ensure maximum safety ancl con:fort ir1 all ridir1c conditions. iiowever, since to:•tW motorcycles are r,urchased for a variety of differeni r,urposes, sorne moJification to the standard version’s settin~s n1ay prove necessary and acceptable. ~~e offer factory_ fitting of t;’”iese special cor.ponents, but the snccial equinme’lt can, of course, be supplied to you for subsenuent installation. We will accorJincly be issuin~ recommenJations shortly for the correct equipment of any motorcycle with items from our r,ro