Vibration at 4,500 - Possible Causes?

[lwood]

I recently have come upon a vibration that hits the Hyper at 4,500 and continues on up the scale. Vibration is felt in the foot pegs and seat of the pants - not so much in the handlebars.

Bike has 3,000 miles and I just put on new tires front and rear - ensured that the dealer set the chain tightness and wheel alignment. Vibration still continued. I was informed later that a wheel balance or tire balance situation would have caused more of a "hopping" than a vibration. Plus, when the clutch is pulled in, the vibration goes away instantly.

Anyone encountered something like this?

Thanks

Lee
2008 Ducati Hypermotard
2008 BMW R1200GS Adventure

[dukepilot]

Make sure your engine mounts are tightened to the proper torque spec. Check the engine case at the upper motor mount for any cracks.

Originally Posted by lwood

I recently have come upon a vibration that hits the Hyper at 4,500 and continues on up the scale. Vibration is felt in the foot pegs and seat of the pants - not so much in the handlebars.

Bike has 3,000 miles and I just put on new tires front and rear - ensured that the dealer set the chain tightness and wheel alignment. Vibration still continued. I was informed later that a wheel balance or tire balance situation would have caused more of a "hopping" than a vibration. Plus, when the clutch is pulled in, the vibration goes away instantly.

Anyone encountered something like this?

Thanks

Lee
2008 Ducati Hypermotard
2008 BMW R1200GS Adventure

[dave2riff]

Loose engine mounts are a common cause for this, true, but there can be other
engine related sources of vibration. As the throttle body synchronization gets
further from optimum, roughness can be felt an some RPM's, but mostly lower.
Having the throttle bodies (basically, the throttle plates themselves) re-synched
can help. This is generally done with a dual vacuum gauge setup hooked into
the two small vacuum nipples that were used for the emissions carbon cannister.

Other than a problem with the balancing of the crank assembly itself, which is
unlikely, there are some corner case issues with valve clearances, valve timing,
and grossly lean or rich mixture that can cause vibration above 4k rpm. The
strangest cause for the engine running rough through the midrange I've seen
was an exhaust leak ahead of the oxygen sensor, that would intermittently pull
in fresh air into the exhaust stream and throw off the fuel mixture by confusing
the lambda sensor feedback. Having one of the little CO probe fittings back
out on the header pipe can introduce air into the exhaust ahead of the O2
sensor... but it only seems to pull air in at certain RPM's so the results are
erratic and unpredictable. At 4000-5000 you are in transition to open loop
mode on the fuel injection, so the O2 sensor is still in play if you have one.

Has anyone seen the effect of slipping one tooth on a cam belt? With all the
loose belts out there, I've been wondering how severe or minor slipping one
tooth would be. Do tell!

[lwood]

Originally Posted by dave2riff

Loose engine mounts are a common cause for this, true, but there can be other
engine related sources of vibration. As the throttle body synchronization gets
further from optimum, roughness can be felt an some RPM's, but mostly lower.
Having the throttle bodies (basically, the throttle plates themselves) re-synched
can help. This is generally done with a dual vacuum gauge setup hooked into
the two small vacuum nipples that were used for the emissions carbon cannister.

Other than a problem with the balancing of the crank assembly itself, which is
unlikely, there are some corner case issues with valve clearances, valve timing,
and grossly lean or rich mixture that can cause vibration above 4k rpm. The
strangest cause for the engine running rough through the midrange I've seen
was an exhaust leak ahead of the oxygen sensor, that would intermittently pull
in fresh air into the exhaust stream and throw off the fuel mixture by confusing
the lambda sensor feedback. Having one of the little CO probe fittings back
out on the header pipe can introduce air into the exhaust ahead of the O2
sensor... but it only seems to pull air in at certain RPM's so the results are
erratic and unpredictable. At 4000-5000 you are in transition to open loop
mode on the fuel injection, so the O2 sensor is still in play if you have one.

Has anyone seen the effect of slipping one tooth on a cam belt? With all the
loose belts out there, I've been wondering how severe or minor slipping one
tooth would be. Do tell!

I appreciate all the great input. I will check it out or have it checked out.

Thank you.

Lee

[stygrishir]

Great little topic.
And Nice work--thank you for sharing- for me this makes perfect sense though.