problems with engine performance

[rob smit]

I ride a R1100S with is set up as followed:
Laser exhaust and cat. replacement pipe, air duct removed, no further modifications.
The bike is from 10-'99, now about 20.000 KM.
After work by a dealer on the gearbox (they replaced a axle in the gearbox)I experience the following problem. When I drive on the motorway the bike did sometimes not got above 180 km/h(not miles) it look like it did not get enough petrol, it just did not want to go any faster. When I give it some time at a lower speed it goes faster but just about 10 seconds later it looks like the fuel runs out, and it does slow down again.
After looking for breather- or fuel-lines which got stuck between part or so I did not find anything strange. I measured fuel pressure it look o.k.. I ran it on a dyno-jet bench with a air/fuel ratio meter and it runs fine and looks fine on the ratio(between 15 and 13,and about 94 HP on the backwheel.)
The problem keeps getting worse
Today I rode on the highway and it could not drive more than about 140 km/h.
Does anyone have an idea what is wrong with the bike ?? please let me know.



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[roger albert]

Hmmm,

interesting. The dyno test is normally a pretty good indication of perf under load.

I'd double check all the vac line routing even though you've already checked once. Just because a line isn't pinched, doesn't mean it flows.

1) they can be blocked
2) they can collapese on themeselves under suction
Look for any marginal clearances that could change as the fairing etc shift under wind load.

I note two points also:
1) The dyno simulates neither the benefit of
Ram Air, nor the detriments of low pockets
of pressure in the fairing. (many local
minima and maxima exist around any vehicle
at speed
2) You mention having removed your airduct.
That would be consistent with just the
sort of thing the Dyno doesn't simulate.

I'd try putting the duct back on first.

Did the bike ever hit 180 previously?
How many variables did you juggle simultaneously, i.e. how many mods did you
make after last being able to sustain high speeds. Confused air pressure sensor???

let us know what you find.
later
roger

[roger albert]

p.s.

Vac/air lines are the most obvious, but
intermittend elec lines could cause trouble too. Has a dealer read the diagnostics yet?
If there's a trouble code, or sensor error, modern engine managed motors can often perform well under error/default values, but will certainly not perform well on one or more edges of the envelope (idle, full throttle, heavy loads etc) I really need to learn the Motronic better. I'm still handicapped on Bosch bike FI/mgmt.

later
roger

[rob smit]

I found the problem.
I yesterday, red out the motronic, there where no folds.
It looked like the bikes cylinders we not running evenly so we checked or the were syngroon, the were not so I adjusted it.
Then I changed the petrolfilter, problem stays.
This morning I drove to work and one of the sparkplugs did meltdown. The engine run on one cylinder.
After checking the piston and cylinder through the sparkplug hole is saw it was not damaged.
I replaced the sparkplugs.
Then I checked the sygronisation again, and it was changed again. ???.
Then I checked the valve clearance, from one of the valve the clearance was 0. it was down from 0.15mm to 0 in less than 10.000 (the service interval)
Now it rides like it used to again. Great relieve.
Roger thanks for you help. Greetings Rob

[roger albert]

Hi,

Glad you got it sorted. I guess my advice was bad in a way. When a bike like that comes to me, I check for obvious vent/hose issues, and then go straight to valves. I guess I just, like you, didn't expect that on a newer bike. Personally, on a new motor, I like to check things more often anyway. Sounds like you dodged the damage bullet anyway. I assume the zero-clearance was hot,
no? (zero-cold would almost imply damage at temp) Keep an eye on that valve. If it or
the seat is insufficently hardened, then you could quickly get recesssion and back to inadequate clearance in a hurry. The question is, what was the root cause?

What's your total mileage now? I assume the
full 1000km maint was properly carried out?

later
roger