F650gs starting issue

thecivvie

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Recently my 08 Twin has a weird starting issue. It is almost like the battery is low, which it isn't. The ecu seems to recycle and the clocks on the dash do the start up routine. But the bike starts, albeit a little slowly.

No warning lights showing. Only recently started happening. First time I noticed it, I had stalled and it did it on the restart.

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How are you sure it is not the battery? The stators have a habit of failing which leaves the battery drained
 
Whilst it's worth checking all the neg/earth connections & the leads to the starter, I'm with Alex - this sounds typical of a failing battery. How old is it?

Get you dealer or local bike shop to put in on a load tester if you are struggling to believe it - when you press the button & the starter tries to engage, it probably dips to 11 v or less, although it may show 12.4 plus static after a run.
 
Good sign the battery is on the way out is if the speedo tacho sweep repeats when the engine is running. Im with the advice above. Check terminals arnt loose and if tight get a new battery like a Motobatt or similar.

Cold weather coming that will rapidly see off a failing battery
 
The battery is fairly new. Replaced last year. Stator is also new. Previous owner replaced both last year. May try another battery

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If you have access to a voltmeter you can check the stator and battery very easily (there is a more specific test involving unplugging the modulator and checking the amps from the stator).


Put the voltmeter on the battery, you want to see the following values:
Before you start the bike - 12.3 - 12.6v
Bike running - 14.4v
Immediatley ater turning the bike off - 13.1-13.3v

This won't show up dead cells in the battery but will give you a rough guide which part is giving problems.

I have driven the bike with a failing stator (and the battery going flat). The CANBUS has some tricks to make the bike run as long as possible:
Below 10V lights and ABS tunrn off
Below 8v the instruments turn off


I have a permantly wired (on the sat-nav connector) voltmeter, very useful guage on a 800gs


I had 2 stator's fail in 9 months....
 
I think I will get a voltmeter attacked to it. I know my friend whom I bought the bike off replaced the stator and rec/ref with one of those better ones, name escapes me.

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The battery is fairly new. Replaced last year. Stator is also new. Previous owner replaced both last year.


Age of item is irrelevant. You would not believe how many failures on new electrical items I have had out of the box or shortly thereafter (sometimes months) in my mechanical career. ie fitted brand new oem batteries only to have to replace them 2 weeks/3/6 months later. A case in point - I fitted a brand new OEM rectifier to my F650 about 2 years ago and had to replace it a week later as it failed. Next one fitted - fine (so far!).

The point is, even tho you think it might be allright as it's recent, you should still ALWAYS check these items. My guess is battery (as its giving the classic symptoms) but it could equally be a poor earth or other wiring fault poss even ignition swith contacts.
 
Will be checking them all when I get home from Russia. Something to do on dark winter nights

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OK. Back from Russia and had plastics off. She started fine yesterday but today the voltage in the battery was too low. 11.5v

Running she would not maintain anything above 13.6 volt across the battery.

She was fitted with a mosfet rectifier which after I ran her for 10 minutes was fairly hot. A friend will check the stator output this evening, if I can get her to start. Sadly cannot find the optimate connector for the din socket
//cloud.tapatalk.com/s/59f9aebf50e55/video-ec00e56fa16de7c4873ef4b0e4a9f5c4-V.mp4

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Seems strange - I would have expected your MOSFET to try to raise the voltage in this scenario, so at least 14.5v at 3000 rpm+

Just a thought - have you ever jump started the bike from say a running car in an emergency? These RRs are sensitve & should only be jumped from another static voltage 12v source.
 
Never had to jump start her at all. She suddenly gave up the ghost. I am wondering if the stator is gone.

She has never even been plugged into the optimate as I lost the cable

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Output from the stator is fine. Output from the mosfet regulator is all over the place and peaking at 18v. Oddly never getting that high at the battery. The Can bus must be holding it back

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Any idea why at the rectifier output getting 18v but only 12v at the battery

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If you are 100% sure the stator is OK, but see 18v at the MOSFET RR output, then it sounds like the RR has failed. Should max out at c.14.5V.

Only achieving max 12V at the battery suggests current is leaking to ground/neg somewhere. Have you checked out the wiring loom, connectors, neg/earth points? Do you recall seeing any 'flare' from the headlight as revs increased; maybe blackening witness on the bulb?

Is your MOSFET a Shendengen (good) or a no-name? (not good). Did it come with ready made connectors or was it connected up with crimps/soldered in? I am thinking maybe one of the connectors has been fried internally. Some fitments suggest direct wiring to the battery, rather than via the standard loom - how is yours fitted?

Is your RR in the standard position, RHS behind the engine or was it moved out into the wind, with extended wiring - they can overheat, but should cope with up to 120c ...ish - any more & you may see witness on the rear face.

If the above check out, have you tried another battery in case yours is caput - this was our first reaction to your post remember. Odd things can happen if a battery has been overcharged as the RR would have failed progressively.

Good luck with the gremlin ................... KEN
 
The mosfet I know nothing of the origin as it was there when I bought the bike. It is placed where the original rectifier was. To me that would seem a little warm.

The wiring appears to be original, I cannot see the wires going direct to the battery.

Seeing no flaring when driving, although I did notice today that the reg plate bulb is blown although that maybe nothing.

Current replacement mosfet is from an R1 I think but will be replaced with a good one.

I put the new mosfet on and went for a spin. Then back at home and put the bike back onto the optimate. I saw the optimate talk to the canbus and then go into sleep state.

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Sounds promising, but an Optimate won't detect overcharging - what voltages are showing now, at the battery terminals - stopped & resting/tickover/3000+ rpm ?

Basically you need a Shindengen MOSFET, with BMW F800 connectors, just to be certain. Sadly not a cheap option.
 
There is a Mosfet on it but not BMW connectors.

There is no charge at the battery. Multimeter is. Showing 12.4v sometimes going a little higher but never in the 13+v range.

I plan to pull the plastics off tomorrow and check the wiring. Oddly the light bulb for the number plate has blown but the computer is not telling me

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