It had to happen.... I have finally got rid of my long suffering Tenere and moved up to the world of German engineering and pillion comfort - but all is not yet rosy in the land of BMW. My newly acquired R1100 GS (1995) is using a lot of fuel (8-9 miles to the litre) and is a sod to start on occasion (high speed running is absolutely fine). I thought this was down to the remus can and chip which were on the bike when I bought it, and switched back to the original exhaust and chip, but if anything this made matters worse. She starts with difficulty, and runs quite roughly for a few minutes - seems to recover and run more smoothly after this, but even restarting when warm, if you have left her for more than a few minutes, is a problem.
Any ideas how I should proceed, you beemer experts? I wonder if the mixture is set too rich, and how to go about altering this? Can I do it myself, or does it require dealer attention and a whole bunch of technology type stuff?Should I contact NASA?

Cheers for any suggestions,
C.

Couple of candidates:

o) does your "choke" (it's acctually fast idle) cable works correctly?

i) Check the ignition coil. If you have any friend owning 1100 swop the coil with him like a fellow did once with me - it was a bad coil and he had exacly the similar problem as you have - bad cold/wark start etc and later normal. It's easy job to swop a coil and the new one doesn't cost much eighter.

ii) Check the spark plugs, if they're dark, then the mixture is too rich, brownish is too lean, if light-gray then all is fine with the mixture.

iii) Check that the TPS (throttle position sensor) is between 0.360 to 0.399 volts, this regulates the fuel mixture. More voltage the more rich mixture. But if the TPS is below or above that spec, then the Motronic doesn't "understand" the TPS signal very well. Search around the web how to check the voltage and how to adjust it, it's dead easy if you have a regular multimeter. Altough i'm quite sure the early 1100s had CO-potentiometer to alter mixture as well aside the TPS, the newer ones doesn't have the CO-pot. Ask from the UKGSer about that, also would be good to post this thread there.

iv) Put a new airfilter, new plugs and new fuel filter.

v) Do the valves check and adjustment (easy on a boxer)

vi) Synchronize the throttle bodies and adjust the idle speed (dead easy) (make your own syncronizer).

vii) Check if you have the correct Cat Code Plug (CCP), do you have catalythic converter+lambda sensor model or not?

iix) Take the starter off (dead easy, 2 bolts only, disconnect the battery first), clean it and see if it rotates freely enough. I know one case where the magnet's have got loose in the starter and it makes it rough moving(=bad starting).

My '98 R1100GS takes about 4.8L per 100km to 6L per 100kms depending on the right hand, overall average i get is 5.5 to 5.8 litres per 100kms, i'm not a 'hesitating' type of rider tho (you can do much better than this). But to get your kind of consumption i'd have to wheelie it exiting every corner and traffic light. The maximum consumption i've got is around 7L per 100kms on autobahn two up full of luggage wide bike.

Let us know, if above didn't help. Then let's search a bit more

PS: buy the Haynes or Clymer manual.

All this messing about you have been doing with tuning chips and exhausts has likely confused the motronic unit so a reset would be in order.

Remove fuse 5.
Wait a minute.
Replace fuse 5.
Ignition on.
Fully open and close throttle TWICE.
Ignition off.
Job done.

This is a bit like rebooting your PC - when things start going wrong on the PC, the easiest fix is to reboot . Well a motronic is also a sort of PC in miniature so by rebooting it you tell it to relearn the basic settings of the bike . You may find this will sort out a lot of your problems.
Margus' suggestions are also all very valid but assuming the valves are adjusted correctly I'd definitely try thsi reset sequence and go on from there.

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Thanks for your useful advice, guys - the plot has now thickened considerably - see my more recent posting.....