The starting system on the F650GS and G650GS is complicated by the neutral, clutch and side stand lockouts coupled with the use of a load relief relay to minimise power consumption when starting.
On all models the Load Relief and Motronic relays in particular can cause odd behaviour as they current limiting inbuilt. It is suspected it is a thermal bimetal strip system. The relays are interchangeable for fault finding.
One symptom can be a loss of lights when turning on indicators or other power consuming items.
The diagrams below have the basic control circuits and part information to assist in fault finding.
Neutral Lamp comes on when the side stand is extended. Check diode C on the starter circuit diagram above.
Neutral lamp comes on when the clutch is operated. Check diode B on the starter circuit diagram above.
There are minor pin number differences in the BMS variants, BMS-C, BMS-C2 and BMS-E so there are 3 diagrams.
Relays in the electrical box are all the same Tyco relays. A specification pdf is below.
The relays are interchangeable and common to all the F and G series GS models.
The Motronic Relay controls power to the BMSC via the starter diode circuits.
The Load Relief Relay simply removes power from the headlight while starting,
operation of the relay is independent of the starter diode circuits.
The Diode Relay is simply a 7 pin relay housing with 4 diodes mounted inside.
It is built specifically for the GS. Other diode relays will not work.
650X diode relays are different to the GS plus ABS & non ABS 650X relays are different.
BMW use 3 diodes in the starter circuits. Two are in the Diode Relay and one is encapsulated in a plastic case with spade connectors.
BMW diodes are ceramic encapsulated diodes, they are brittle and can break. In addition BMW use ultrasonic welding which can cause poor connections with vibration, soldering diodes is mechanically more robust.BMW Diode Specifications Alternative Diode Specifications
Electronics stores stock alternatives to the BMW diodes.
The 1N series replacements are plastic encapsulated and more robust but larger. soldering the diodes is mechanically more robust.
The diode repair page has details on diode replacement.
The load relief relay is a little tricky, the relay operating coil has power from ignition (green wire) on one side and the other side (black wire) goes to the power side of the starter motor so when the starter button is pressed there is power on both sides of the operating coil and the relay turns off. When the starter button is not pressed the relay coil earths through the starter motor which is low in resistance (measured at 1.2 ohms).
Note the single spark diagrams show the black wire going between the Load Relief Relay and Starter Relay output.
Take care to ensure the stand is up if the switch is bypassed.
The Starter Solenoid looks like those on other makes and models.
The Mfr/Part No on the others is not the same as on the BMW unit
Others may able able to be used in repairs "out on the road"
The Mfr's seem to be Denso, Jideco, Hitachi.
Under the rubber covers are screw teminals for connections.
Funduro F650 - BMW 61 31 2 346 444, Motobins 71375
F/G 650GS - BMW 61 31 2 346 566, Jideco MS5D-731
Yamaha - Used on many models - 4KD-81940-00
There is little in the way of specifications for the starter motor. The manual only states the power rating
as 0.9Kw. This would suggest a continuous current of 75 amps. Euromotoelectrics specify the BMW one as a Denso 228000-6900.
Their replacement for F650GS single and F800 twin is rated at 0.5 Kw cranking torque @ 225 amps.
F650/F650GS/F650CS - BMW Part No 12 41 2 343 511, G650GS/F650X/Sertao - BMW Part No 12 41 7 699 379
The GS650GS Denso model is 428000-4260. The repair kit is common to all models. Part No 12 41 2 343 512