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2004 twin spark Rockster. 65,000 miles.

Posted before about increased fuel
Consumption over this winter but now there's more problems
Along with the 10% increase in fuel consumption there has also been increased vibration, more of a buzz felt through the pegs and seat. Suspecting throttle body balance I bought some Davida gauges and set to..... no difference. Had another go and again no difference. Riding along on Saturday I had a thought, pulled over and did a motronic reset. This made the bike run a lot smoother.
So thinking things were back to normal went to Prescott with Mrs.tree yesterday and things were not right. The buzzing returned and there was also a loss of performance..... most noticeable when nipping past a car, the zap of acceleration had gone. Then, on the way home, rolled the throttle open to pass a car and there was about a second of heavy pinking and loss of power, then things picked up and completed the overtake. Pulled over and checked what I could, nothing obvious. Stick coils ok (new last year). Started up and ran fine, no
ominous noises. Plugs look good.
Still at work at the moment but I'm stumped where to start with this. I've got a compression testing gauge so I imagine that's a good idea , owt else?

Intake clear, airfilter clog. Exhaust clear. Water in the fuel or bad petrol.
I have seen all of this at one time or another that will cause similar symptoms. Had a mouse fill the exhaust can 1/2 full of dog food!
Also corrosion in electrical connectors but that's a stretch.

Probably not a mechanical problem like compression, something peripheral.

Somebody remind me: what are sysmptoms of the intake manifold leaks?
Same as worn throttle body shaft?

sweatmark wrote:Somebody remind me: what are sysmptoms of the intake manifold leaks?
Same as worn throttle body shaft?

assuming timing is spot on....

depends on whether the leak is before or after fuel introduced. but irregular or high rpm is a telltale sign. On the boxer I think it could be a problem here. maybe a vacuum leak...How I was always taught to check this, let it idle and spray carb cleaner near all the seals and vacuum connections. Idle goes up or changes, you have a leak at that spot.


then fuel quality/delivery. filter/pump...


off chance:

check that plugs into fuel injectors are fully seated, and making contact. Chris Harris has a youtube vid where he spent HOURS thinking it was a motor, only to find out one of the pins was pushed back into the connector not making contact all the time.