This is to help another BMW Club UK member.

1997 K1100LT, bought on a whim!

The bike starts easily and at idle sounds perfect.

Go for a spin and it starts to run rough (on 3 cylinders). each time it seems to be number 4 plug fouled up/flooded.

Jobs performs so far:

Compression check - Good 
It has a new fuel pump and fuel filter.
The injectors were checked and showed to have a similar spray pattern.
Throttle bodies balanced.
Fuel pressure checked and seems o.k.
New plugs fitted.
Replacement plug leads & coils (from my known good K1100)
Replaced TPS (From my known good K1100) 
ECU swapped out (as above)
Electrical connections to ECU,  coil etc. checked and cleaned (but not found to be bad anyway.
The Hall sensor has been changed and ignition retimed (on the original the timing was out). Since then the old hall sensor has been refitted with no improvement.
I have measured the resistance of the coolant sensor from the ECU cable connector. This is different pins to the K100, but all seemed o.k.

I have requested he check the valve clearances, and swap over the injector from number 4.

Any more ideas?

Mike

I had a similar problem on my K100 16V - turned out to be a bad connection on no 4 injector - when I swapped the injector cable with no 3 the problem followed and was then easily fixed by repairing the bad connection on the no 4 injector cable.

I had to strip back the hard rubber covering of the injector plug connector to find the problem.


Since you have a spare it might be worth temporarily replacing the whole fuel injection loom

Thanks,

Worth a go. Will ask him to swap the connectors over (or at least give them a good looking at!

Mike

O.k. so time for an update. 

The #2 inlet valve - cyl 1 (working from the front of the bike) is tight at 0.08mm. 

The #5 exhaust valve - cylinder 3 is loose at 0.38mm 

All other clearances are within spec. 

Now if the problem had been valves on cylinder 4 I would be more happy, but at least this is the first hard fault we have found!. 

He hasn't as yet swapped over the injector electrical connections or the injectors themselves (I did ask him to do this before checking the valves). 

So, knowing a valve is tight, but only one of the two on a different cylinder to that which was suspect, could this be the actual fault.? 

Mike

I don't think that it is the problem, if it was a loose inlet and tight exhaust it would be more likely but still I would not expect that to be a problem.
I chased a similar problem with my K1100 and it turned out to be a slightly retarded TPS. It was only a matter of about 0.5mm at the screws but what a difference. It was OK cold but as soon as it got to operating temp the #2&3 cyl would start missing. Since I got it right it has been running well. Because it was 2&3 cylinders I was chasing and intermittent electrical problem.

Hi Rick,

Thanks for the feedback. The TPS has been swapped for a known good unit (mine) and set using a GS-911 (plus Charlie has also used a multimeter to set it), so I don't think that is the issue. Plus of course it only seems to be missing on number 4 cy;inder.

I may try to get back to visit him this wee, but he is an hour away and I will be doing some part time work this week.

Will post another update when some more testing has been completed.

Mike