Manual - Chapter 5 - Fuel & Oil

16: Throttle butterfly assembly and plenum chamber: removal and refitting

  1. On K100 RS, K100 RT and K100 L T models remove the fairing knee pads, radiator cover and lower side panels. On K75 S models, owners may wish to remove the fairing side panels, or at least their bottom covers, to gain easier access. On all other models, remove the radiator cover panels. See Chapter 7 - Frame &Forks.
  2. Remove the fuel tank. See Section 5.
  3. Note: The clips securing the plenum chamber to the throttle butterfly assembly are of a special type which must be broken to remove them and must be renewed, and fastened using a special tool, on refitting. To avoid the need for this it is recommended that the throttle butterfly assembly and plenum chamber are removed as a single unit, as described below.
  4. Referring to Section 14 of this Chapter withdraw the air filter housing top half and the filter element; there is no need to separate the airflow meter connection but the connecting hose must be disconnected from the plenum chamber.
  5. Slacken its clamp and withdraw the crankcase breather hose from the plenum chamber stub. Note that if its retaining clips are to be broken and renewed, the plenum chamber can now be withdrawn from the machine. On refitting, apply a smear of lubricant to the air filter connecting hose and to the rubber stubs connecting it to the throttle butterfly mouths. Ease the chamber into place, ensuring that the pieces of insulating material are correctly positioned, and settle it fully into place before securing the hose clamps. Note that those fastening the throttle butterfly assembly unions are secured with BMW tool number 13 1 500.
  6. Remove the fuel rail and injectors. See Section 13.
  7. Slacken their adjuster locknuts and screw in the adjusters to gain the maximum free play in the throttle and choke control cables, then disconnect the cable end nipples from their operating levers and withdraw the outer cables from their brackets. Disconnect the throttle position switch at its connector plug, then either unscrew from its mounting bracket or disconnect at the main wiring loom the choke warning lamp switch.
  8. Slacken the intake stub securing clamps and withdraw the throttle butterfly assembly and plenum chamber. Note how the clamps are positioned to clear the throttle operating mechanism components. Each intake stub is secured by two screws or bolts.
  9. The pressure regulator, vacuum switch (early 100 models only) and choke warning lamp switch can be removed, if required.
  10. Do not attempt to dismantle the throttle butterfly assembly further, and never disturb the screws linking the butterfly operating arms. Since the bypass screws provide only a limited adjustment it will not be possible to ensure accurate synchronisation if the butterflies are disturbed; they are set at the factory and can only be renewed as a single assembly.
  11. On refitting, apply a thin coat of sealant to the stub mating surfaces and tighten the mounting screws or bolts securely, to the specified torque wrench setting, where given.
  12. Refit the throttle butterfly assembly to the stubs and check that the clamp screws are positioned so that they can be secured, but so that they are well clear of any part of the throttle mechanism; operate the mechanism throughout its full travel to check that it is completely clear.
  13. Connect (or refit, as applicable) the throttle position switch and choke warning lamp switch.
  14. Connect and adjust the throttle and choke control cables.
  15. Refit the fuel rail and injectors, then connect the crankcase breather hose to its stub.
  16. Refit the air filter element and housing top half, then refit the fuel tank.
  17. Check the idle speed setting and the operation of the choke and throttle controls. lf necessary, check the synchronisation of the throttle butterfly bypass screws.
  18. Refit the radiator cover panels or fairing components as applicable.

16.5 Disconnect crankcase breather hose from plenum chamber stub

16.7a Disconnect throttle and choke control cables

16.7b Disengage wire clip before disconnecting throttle switch plug

16.8a Removing the throttle butterfly assembly and plenum chamber

16.8b Check intake stubs for splits or damage - renew if necessary

16.10a Never attempt to dismantle any part of butterfly assembly ...

16.10b ... and do not disturb screws linking butterflies