Engine Vibration

profWacko · 07-03-2003, 05:27 PM

I know that this is rather subjective to talk about because words cannot describe a feeling very well, but...

When I spin the motor up above 6k rpm, I get a pretty severe high-frequency buzz that feels more like a 4-cylinder-type of vibration. Even my KTM Duke vibrates less at 75% of redline.

I have just set the valve clearances (they were all loose by quite a bit) and put on the Twin-Max for a sync test. The sync was only off at 4k rpm by about the width of the indicator needle, so I decided not to adjust anything for fear of making it worse.

I read where some guys have forgotten to shift and found themselves cruising down the freeway at 6500 rpm in 4th. That would NEVER happen on my bike the way it is right now.

I am thinking of hooking up the Twin-Max so that I can do a ride-test with it connected to see what that tells me.

Any thoughts out there in Guru-Land?

PS: Bike is completely stock but for cannister removal by previous owner. TPS screw paint from factory still intact. Almost 8700 miles.

markjenn · 07-03-2003, 09:33 PM

Mine also buzzes quite a bit above 6K. Some are smoother than others, but I suspect yours is within normal bounds. I doubt there are many riders who ride around at 6.5K+ because they forgot to shift.

I'd try and ride a dealer's demo bike to confirm.

- Mark

MarkC · 07-04-2003, 12:27 AM

Take a quick look at the rubber damper at the frame where the CAT mounts. I just replaced mine a few days back (it was cracked), incidentally, another member here just had the same prob.

Also, if the throttle synch differs as the RPMs change, then the valve clearance on one cylinder may be off, or you could have an air leak at the rubber intake manifold.
MarkC

profWacko · 07-04-2003, 08:32 AM

Air leak sounds more and more likely.

It seems to vibrate less when cold and does not really get bad until it is really up to temperature, like after a run up and down the Crest. Afterwards when getting on the freeway, it goes into vibe city.

Perhaps I will get someone to look into exactly what changs were made when the cannister plumbing came off.

Thanks for the input.

roger albert · 07-04-2003, 08:47 AM

Unless heavily medicated, I can't imagine who is claiming to buzz (literally) around at 6.5k rpm and not know it. Myabe on a K12, but not on our beasts. If you're sync is good, then you don't have an airleak. This is unfortunately the rocking couple induced normal vibration from a big opposed twin. They do vary a bit, but I doubt (sorry to report) that things are far amiss with yours

nature of the beast I"m afraid

roger