Testing coils - 2008 GSA

metropolis2k

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Hi folks. When my bike is hot it runs very poorly and stalls easily, and I suspect it’s the coils so I’m trying Steptoe’s diagnosis technique.

Tried combinations of coils unplugged tonight and here’s the results. Can anyone smarter than me tell me what it means before I end up replacing all 4 in hope?

Running on primary coils only: Wants to stall at low revs but otherwise ok
Running on secondary coils only: Better low down but no power accelerating in 4th
Primary left and secondary right coil: As above, no power in 4th
Primary right and secondary left coil: Stalled at low revs but ran ok ish under load.

Thanks in advance!
 
Crappy primary left??

Try all four then minus the primary left and see if it changes. Only guesswork from what you’ve reported on and there will be more experienced than me along shortly.

Perhaps given that one is failing, purchasing a pair of primaries may be wise.
 
Thanks, think I need to do both those things - pull all the plugs and see if they tell me anything, and also try just pulling one plug at a time.
 
BMW aren't that clever - they die to time - not one good one lasts forever and a few unlucky people get an odd random failure

fit 4 move on
 
Plugs seem to be fine. Lower ones are slightly darker but only by a bit. Only other odd thing was some gunge on the threads of the left upper one.

Does this suggest the coils aren't the problem?

PbZYpjnl.jpg
 


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