improved-valves-for-unleaded-11-043-90-2412-690

( Service-InformationM otorcycle Group: ©BMW of N.A. Service Department 11 Engine June 1990 11 043 90 (2412) For USA Only ImprovedB oxer Valve Component-s UnleadedF uel The evolution of the Boxer engine, due to emission contro7s and changing fuels, has resulted in a net increase in combustion :emperatures from 1978 to present. Over this period of time numerous changes have been made to components to maintain engine reliability at these higher temperatures. The changes made to the 1988 and later RlOO models have proven so effective in minimizing valve lash wear between service intervals that these components have been adapted for a 11 previous Boxer engines and are available through Spare Parts as follows: Exhaust Valve Seat: Valve Guide: Exhaust ,.Va] ve: Current Improved alloy greatly increases heat transfer between valve and cylinder head to eliminate valve recession, yet be compatible with unleaded fuels. Improved al lay increases heat conductivity between valve and cylinder head. This also reduces tendency to overheat va 1 ves. On RlOO models, a 30° valve seat face is used to increase the heat transfer areas (wider seat width). / listed part numbers: ~bD7 1.,, RlOO Exhaust Valve 30 °x 40 mm 0 11 34 l 338 285 _; . “”~ Exhaust Valve Seats: A.,, RlOO ~oo x 40 mm0 + 2 mm 11 12 1 338 308” +4mmll 12 l 338 309/ *RlOO 45° X 40 mm 0 + 2 mm 95 12 l 338 308 + 4 mm 95 l’2 1 338 309 R90/90S 45° X 40 mm 0 + 2 mm 11 12 1 338 3431 +· 4 mm 11 12 l 333 344 R75 45° X 38 mm 0 + 2 mm 11 12 1 337 ·agg + 4 mm 11 12 1 337 900 R60 45° X 36 fl11l 0 + 2 mm 11 12 1 338 346 + 4 mm 11 12 1 338 147 RSO 45° x 34 mm 0 + 2 mm 11 12 1 337 894 + 4 mm 11 12 1 337 895 *On pre-1988 RlOO models with 45° valves, if replacement valves are not JI~ needed, a special seat has been made to enable you to bring the valve seat width at 45° to a full 2 mm. For this reason we do not recommend the seat listed (part nos. 11 12 1 338 349 & 11 12 l 338 35G) on the Parts Fiche for this application, as a 2 mm wide seat face cannot be achieved. Please initial and route to the following before filing l; ..S ervice Parts Sales Warranty Technicians ….- – Valve Guide: Unleaded Fuels: **14.06 mm O Standard 14.25 mm O Over-Size 11 12 1 338 433 11 12 1 338 445 **This is a standard replacement guide which is pre-reamed for precise replacement fit. Only the new exhaust valve seats are required when converting an older model for unleaded fuel use. Replace the valves or intake valve seats only if they are worn beyond specifications, as no modification to these parts is required for exclusive use of unleaded fuels. We recommend that valve seat. installation be entrusted only to a workshop specializing in this type of repair, utilizing approved BMW procedures. A bulletin will be forthcoming with valve seat installation details. Please refer to the Parts Pricing circular you will be receiving regarding the prices of the aforementioned parts. Many prices have been reduced since the June, 1990 Price Book. Very truly yours, BMWof North America, Inc. Frank Stevens National Service Manager FS:jel/255.7 Richard Dampf National Technical Manager