Loss of Acceleration R1150RA

[Karter]

I've been having a loss of acceleration or very slow acceleration lately. I'll throttle back and the RPMs will rise, but it takes a few seconds for the engine to catch up. the bikes a 2004 R1150RA with about 17500 miles on it. I've replaced the stick coils, spark plugs, MCU all in the past 18 months and even had the gearbox rebuilt a few years ago (overseas). Last summer, i had some knocking in the engine, which went away with some gas cleaner.

Can it be an issue with the fuel filter? Timing Belt? Anyone have any ideas.

[NoRRmad]

Your description's a little ambiguous, ("throttle back and RPM's will rise"?) but it sounds a bit like clutch slippage, assuming I understand what's happening.

[Karter]

thanks for the speedy response. basically, i'm trying to accelerate, whether its from a stop or shifting gears, and the bike responds, but very slowly. where as i use to be able to get out in front of traffic from a light, or speed onto the highway from the on-ramp, the bike is slow to pick up its pace. it does reach speed eventually, but not in the time frame it should be.

[AndyRR]

Just checking - do the engine RPMs spin up without the bike's speed increasing?
If not, does everything sound normal or is it pinging, missing, etc...?

[grwrockster]

I'll throttle back and the RPMs will rise, but it takes a few seconds for the engine to catch up

When I first read this I instantly thought..... if the throttle is opened and the engine bogs down, and then the engine picks up when the throttle is rolled off - then that would suggest a fuelling problem maybe? As in a big 'flat spot' when trying to feed in throttle?

If that is the case, then that behaviour would perhaps suggest either too much fuel, or not enough air, or perhaps failing spark (as in no ignition advance perhaps?). As the stick coils have been changed, then I assume they can be safely eliminated?

I don't know enough about it myself - but could a dodgy Hall Effect sensor cause this behaviour? I'm thinking that an air filter being THAT badly blocked at 17.5K miles to strangle the engine sounds unlikely, and that the injection system overfuelling enough to choke the engine also seems a long shot.

As another cause I suppose fuel starvation is possible..... so yes, a blocked fuel filter, or a blocked tank breather (try opening the tank filler - if there's a vaccum then iot could be that, although you'd expect that to actually stop the bike?). The only reason I didn't consider this higher up the list would be (if my interpretation of the behaviour from the description is correct) is that there seems plenty of fuel as soon as the throttle is backed-off to let the machine accellerate.

It costs nothing to investigate the air filter and the intake to make sure they are clean/clear, so I'd do that anyhow - it's something nice & simple to eliminate. But I think you'd be very lucky if it was just that.

Sorry I'm not clever enough to have a definitive answer - hopefully though it'll provide some food for thought though.

G.

G.

[Sunbeemer]

My best guess is that your fuel filter may be clogged. As you give it lots of throttle the fuel can't be delivered in quantity necessary to give the right air-fuel ratio when the throttle plates are opened so wide and the engine bogs down, but when the throttle is backed off, reducing the admitted air, then the restricted fuel being delivered can be burned. A partially clogged fuel filter is a likely source of restriction, but it could also be a failing fuel-pressure regulator, or perhaps even water in the gas. So you might try some fuel conditioner additive, like Sea-Foam, to see if it helps before tearing into anything.

Good luck and let us know how it turns out.