11S is way down on power in upper rev range. suggestions?
 

My, new to me, 2004 R1100S has not been running well since I've taken ownership.

Symptom: It has plenty of torque low in the RPM range up to about 5K RPM and then hits a serious flat spot from there on up. If, at 5K RPM, I whack the throttle open, there is an increase in the intake noise but very little acceleration.

I've tried several things, mostly the easy things that I was going to do anyway, to no avail. I'd very much appreciate your collective experience / guidance since the future list is more involved.

So far I've:

• checked the compression: 125 psi cold / 155 psi hot in both cylinders
• replaced all four spark plugs
• replaced both injectors with known good ones from my other S
• synched the throttle bodies

On my list of to be investigated potential causes:

• clogged fuel filter
• weak fuel pump
• clogged catalytic converter
• weak coils (how do you tests these on a dual spark anyway?)

Am I missing any? Electrical components? Any suggestions on how to best diagnose or eliminate potential causes?

From your experience, which are the most probable?

double check cam timing. previous owner may have messed with it.

Thanks Bill. The PO bought it new and had the dealer do all the service, even oil changes. Hence, cam timing changes are unlikely. In any event, I'll put it on the list.

Given the symptom, which of the list of potential causes do you think the most likely?

Two Words
 

Stick coil.

Had the same exact problem with my '04 R1100S a few months ago.

Another forum reader out of Chicago with a R1200S had the same issue you had about six months ago.

Stick coil replacment.

He is happy.

Sounds like a coil problem to me as well. On a previous bike I had a similar intermittent power loss that would on present after riding for a while and the coil got hot.

low fuel pressure is a possibility. had a r1100r in my shop with same symptoms. fuel filter split open at the seam.

wouldnt hurt to check intake for an obstruction like a bird nest

I had a 04 with 3 bad coils that still ran.
not well though

Had a mouse nest on an Sv do the same thing.

Thank you gentlemen for your kind assistance and suggestions.

I started the engine and let it idle and pulled the plug wires in succession. The right side primary plug wire had no effect whether attached or detached. Bad stick coil. Very easy diagnosis.

I had assumed the failure mode would be intermittent but apparently when these coils fail, they fail completely and the secondary plug keeps it running, sort of, and masks the failure.

Lone Star BMW, my local dealer, had one in stock. I bought and installed it and this baby is now running nice and smooth. :) All's good in TX (excepting our Governor).

yeah Texas, oh yeah tell us about the Chisolm Trail please..:cool: