which coils?

[demito]

Hi all,

Since a little while I have noticed the following behaviour on my bike (2004 1150GSA twin spark):

-fuel consumption going up (used to do 480-500 kms with a tankful, 30L adv tank, now 410kms). Riding behaviour has not changed. A lot of motorways.
-when hot, the bike kind of hesitates around 4500 rpm. The hotter outside, the more noticeable. Problem only noticeable with a hot engine.
-With a cold engine, idle is smooth, with a hot engine it isn't. It's like it sometimes misses a beat.
-The engine cut out twice when making a U turn . Never had that before.
-since removing the cat, the bike sometimes backfires (unburnt fuel?). I have noticed some air leaks at the Y piece junctions (black deposit leaking).


New plugs make the bike behave a little better, allthough that doesn't last very long.

I have read a couple of threads and the symptoms seem to point at faulty coils. Which ones do I have to look after (location, pics)? Can one see from the outside it is faulty?
Cost to replace? Other suggestions?

Tnx for your help all.
Cheers

Demito

 

[Flipfly]

The backfire is kinda standard issue on GS's especially if you remove cat. Try sealing the gaps in the Y piece as any gaps will make the problem worse. I would assume that the fuel usage increase may also be allied to you removing the Cat.
I have a Y piece and mine backfires like a cannon and sometimes pops and stalls from time to time. Again I don't think this is too unusual. As for the difference between hot and cold running I'm not sure. I again assume that you replaced the sensor when you removed the Cat.
If your plugs are not lasting long it would point to the coils but I would make sure everything else is fine before spending the money.

 

[demito]

The backfire is kinda standard issue on GS's especially if you remove cat. Try sealing the gaps in the Y piece as any gaps will make the problem worse. I would assume that the fuel usage increase may also be allied to you removing the Cat.
I have a Y piece and mine backfires like a cannon and sometimes pops and stalls from time to time. Again I don't think this is too unusual. As for the difference between hot and cold running I'm not sure. I again assume that you replaced the sensor when you removed the Cat.
If your plugs are not lasting long it would point to the coils but I would make sure everything else is fine before spending the money.

Tnx Flipfly,

just a detail: the fuel consumption/staggering started BEFORE I removed the cat. I could accept a slight increase in fuel consumption if only the cat were to blame, but we are talking +15 % here.

Cheers

Demito

 

[trotsky]

The engine cut off sounds familiar - I had the same thing earlier this year and hauled it off to Steptoe thinking I might be in for a new set of Hall sensors. He whipped the ignition coil bits off his bike and put them on mine and all was sweetness and light. Then he took them back and told me he didn't have any spares so he'd need to get some for me so I had another couple of days of problems before I got it fixed.

They are the coils that fit on to the spark plug in the end of the cylinder and connect from the cable to the plug (the bits the little plastic gadget in the toolkit are supposed to help you remove). The part number for them is 12137671896 (taken from the Max BMW fiche at http://www.maxbmwmotorcycles.com/fiche/fiche.asp) and Steptoe "recommended" buying new one's rather than secoind hand. When Steppers took mine out they were (a) bloody hot and (b) corroded at the plug end so it was pretty obvious they were sick.