bmw 850gs cuts out and won't restart
 

hi everyone
bmw 850gs 2000 starts then runs fine for a few mins then rev gauge starts flickering up and down then cuts out and won't restart but if i recharge battery it start again then cuts out again

can anyone help
please

Is the battery dead after running for just a few minutes? If so, it is almost certainly a bad battery with an internal short that is draining the charge off. If it still turns over easily but just won't start it's is something else. If so, we need more symptoms! Do you have access to a multi-meter?

An erratic rev counter is supposed to be a symptom of a faulty Hall Effect Sensor.

A couple of tests for the 1150 model. Maybe the same for the 850: Crank the engine by hand , e.g with a spanner on the crank pulley. The fuel pump should prime. (Ignition on obviously)
Disconnect HES, crank the engine by hand , measure output from HES with multimeter. Should be 5V approx.

When you say rev gauge - are you talking about the 'rev counter' or the 'fuel gauge'? If the fuel gauge is going bonkers it will likely be the battery. Its a classic sign of duff battery especially as you mentioned having charged it beforehand.

i charged the battery up again started bike again tested battery got 13.86 volts so its charging then it ran for 5 mins again and revs counter started jumping and cut out. someone said it could be an injector loose but i don't know where the injector cables are :helpsmilie:

Rev Counter
Is the rev counter reflecting the engine speed?

No? Then why does the motor stop...

Yes... then proceed with this next bit.

Battery
What is the battery voltage after the motor stops?

If over say 12.5 volts then proceed with the next bit.

HES Hall Effect Switch
Remove one spark plug. Hold the metal body of the spark plug against the engine. Reattach the spark plug lead. Using the starter motor turn over the engine (i.e. try to start it). Do you see sparks from the spark plug?

No? Probably the HES failure,

Yes... not the HES.

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Separate up the steps to find the problem. Work in a logical fashion and record what you have done. This will help, both yourself and anyone else trying to help you.

hi warin could you tell me where the switch is on the bike i haven't got a man for the bike cheers by the looks of it you might be on the right problem:rofl:

On the parallel twin I don't know where the HES is. It will be either ón' the crankshaft or the cam shaft. I know where it is for teh airheads, oilheads and old K models.

Once you find it, repeat the test again, when the bike stops – cool the HES (throw some water over it – avoid getting any electrical connectors wet) and see if it will then start. Buy cooling the HES alone you can confirm that as your problem.

Replacement from BMW would be around the $300 mark, alternatively you may source one from an electronics supplier for around $30 – you then have the job of removing the old ones rivets and cutting its wires, then you rivet the new one in place and solder the wires and insulate the new joint.

It is usually the insulation perishing on the HES wiring, it runs behind the black plastic cover on the front of the motor to the big block of connectors under the front of the tank, you will need to remove the alt belt and the crank pulley, real cheapskates have been known to just solder in new wires to good effect.

That description fits an oil head (R1xxx) yes. On the 800 parallel twin?

Arrg .. it an R850GS .. that did not enter my thinkin... it is an oil head so ... yes as you say Stewart.