Hi,
I haven't used my bike much this winter but, when I have everything seems to have been fine. I replaced the battery a few weeks ago as it has struggled to start at times and failed completely once when I made a short stop.
The new battery has transformed the starting. This morning, though, it has developed a serious misfire. The symptoms are that it just seems to keep cutting out and then pick up again. This seems to be at all times - when accelerating, on a steady throttle and when slowing down.
It started OK and idled on the choke when I left home but after a mile or so started to misbehave.
The first half of my 20 mile commute is at about 40 mph and the second half at motorway speeds. As far as I could tell, it was bad all the way and when idling as I parked at work.
I'll go out and check it will start when it has cooled down and that nothing has come loose under the seat but any thoughts?
I have to say that, apart from oil, battery, brake and tyre changes, it is pretty neglected so I guess it could be the air filter is clogged and I've never attempted to touch the fuel system but I thought I'd ask for any pointers as I don't really want to strip it down to fix!
Thanks
Mark

Usual suspects:

1-Fuel level sender connector
2-Ignition switch

duck wrote:Usual suspects:

1-Fuel level sender connector
2-Ignition switch

Great. Thank you. I wouldn't have thought of either of those. I'll have to see if I can limp home tonight then see if I can check them.
Thanks, again.

Check that the ECU's multi-pin plug is firmly pressed home, especially since the recent battery change. Things mighta got moved round a bit during the operation.

Two Wheels Better wrote:Check that the ECU's multi-pin plug is firmly pressed home, especially since the recent battery change. Things mighta got moved round a bit during the operation.

Thanks. I've just been out to check that everything is still in place and secure. I pushed the multi-pin plug and nothing seemed to move but the bike started up OK and ran nicely so, I hope, things may be OK and I just dislodged something when I fitted the new battery. If not, I'll be trying to find the fuel level sender connector!
Thanks, again
Mark

ajsm18 wrote:

duck wrote:Usual suspects:

1-Fuel level sender connector
2-Ignition switch

Great. Thank you. I wouldn't have thought of either of those. I'll have to see if I can limp home tonight then see if I can check them.
Thanks, again.

Fuel level sender check:  Remove right battery cover.  Shake that connector while idling on the side/center stand to see if that causes issues.

It's the four-pin connector: there's two two-pin connectors there as well (speedo and brake).

Thanks, all, for your help. I was feeling a bit fed up this morning and wondering if I should get rid of it and get something else but now feel a bit more confident in it!
Mark

We've got your back
Sounds like a bad connection, connector.
As said, could be tye 4-pin to the pump, or the big one in the EFI under the seat.
Take it off and on several times, plug everything back, and start the bike again.

The first time I messed with my battery I had mis-firing issues after. It turned out that I hadn’t relocated the EFI connector properly, it has to be hooked into the unit at the front and positively clicked into place over the little plastic ‘speed bump’ at the back (the bit that silly silver thing releases when you take out the underseat tray) If not it will work loose. 
After the second time (yes, yes, I know) I wrapped the connector and unit with a cable tie to make sure it all stayed nice and snug.

I thought I'd report back. After fiddling with everything under the seat and, although I didn't feel anything was loose, the bike started and ran well. I got home again safely and all is well in my BMW world so thanks for your help, everyone. If only fixing badly running Brit bikes was as easy...

Once again, thank you all so much for your kind help.

Mark

  is it fix-ed, a fluke perhaps, or just some crud or a dislodged pin in a connector?

Glad to hear the bad misfire is now a good misfire!

Serious crisis averted.

Two Wheels Better wrote:  is it fix-ed, a fluke perhaps, or just some crud or a dislodged pin in a connector?

Glad to hear the bad misfire is now a good misfire!

Serious crisis averted.

I think I must have knocked something when I was using the accessory socket at the weekend.