Vibration - BMW Luxury Touring Community
 
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post #1 of 10 Old Sep 20th, 2006, 11:21 am Thread Starter
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Vibration

I've got a vibration between 4200 and 4500 rpm. Smooth up to this point and after this point. It vibrates in this rpm range. I can feel it throught the seat and can't isolate whether engine or gearbox, etc. Anyone else experienced this?

Jamie Kiel
2002 K1200LT Silver
2005 Harley Davidson Springer Classic
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post #2 of 10 Old Sep 20th, 2006, 11:44 am
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This is a well-known "feature". Do a search on "4200" (or similar number); you'll get several threads on it.

Not to worry: it's normal.

Howard Schisler
2015 BMW K1600GTL
2009 BMW K1200LT - 60k miles
2012 BMW F650GS (sold)
2005 BMW K1200LT - "Gray Ghost", traded at 120k miles
2005 Honda Shadow 650 (sold)
AMA, IBA, BMW MOA. CCRs: Braselton 2006, Osage Beach 2007, Duluth 2012


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post #3 of 10 Old Sep 20th, 2006, 1:38 pm
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Many people have mentioned it. I have never noticed it as I don't ride in that rpm range.
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post #4 of 10 Old Sep 20th, 2006, 2:29 pm
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Jamie,

It is what is know as the K buzz. The newer bikes do it at about 3800 rpm the older ones at 4200 4400 or so. Has to do with resonance in the exhaust system. I think those that went with Rhemus exhausts altered the point it comes on as well. I just avoid that rpm if I can.

John
2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable
K4AN

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

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post #5 of 10 Old Sep 20th, 2006, 4:28 pm
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Mine's a little higher than that 4.8 to 5.2. But there is a simple solution, downshift and keep the RPMs above that point.

Joel
'02 K1200LTC
"Mauve Mile-Eater"
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post #6 of 10 Old Sep 20th, 2006, 6:20 pm
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You don't need to take the vibes for granted. See also this post. Each inlet canal has it's own vacuum curve through the revs, resulting in varying imbalance at varying motorspeed. The throttle valves can be synchronized at the motorspeed you run the bike most (probably around 4000 rpm). Attached you'll find pictures of a vacuum metre showing the imbalance before and the achieved balance after synchronizing. Bike runs SMOOOOOOTH!
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Erwin

R1200GS Adventure LC 2018, Blackstorm/Schieferdunkel Matt/Achatgrau (Triple Black), in full options, BMW Navigator V


R1200GSA LC '18 <- R1200GSA LC '14 <- K1600GTL '12 <- R1200GS Adventure '09 <- K1200GT '07 <- K1200LT '05 <- K1200LT '99 <- K1100LT '95 <- K75RT '92
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post #7 of 10 Old Sep 20th, 2006, 8:00 pm
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Never thought of that Erwin. I have sync'ed several SU carbs over the years and never thought the LT would be that far off- now I have to check mine. I think this is the first post I have seen on this. Thanks

John
2009 K1300GT Red Rocket
2009 R1200GS (Gone)
2005 K1200LT Ocean Blue Blue Wizard 110 K and counting...
2006 Bushtec Turbo+2 Spell
2004 330 Ci Convertable
K4AN

Have ridden a Motorcycle in all 48
But lack DE, MA, RI and CT with the 2005 LT

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post #8 of 10 Old Sep 21st, 2006, 6:31 am
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There was another post about this a year or so ago. If I remember right the forth cylinder throttle body is the "master" and you sync the other three to it. You can do it with a carb stick like the pictures or one of the electronic flow meters the airhead guys use. The problem looks to be getting to the adjustment screws and the lock nuts. The sensor lines for the meter/carb stick go on the vacuum line ports from the crankcase vent.

Bill McAllister
St. Louis, MO.
2003 K1200LTE
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post #9 of 10 Old Sep 21st, 2006, 6:47 am
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Like I said im my referred post:
Quote:
Originally Posted by ®win
There is a cure, only it is not supported by BMW. Let me try to explain (I don't know all the exact techy terms, but I hope the basic principle will become clear.

The throttle valve unit is produced by Bing and all units leaving the factory have nearly the same settings. After assembly @ BMW, the engine is not adjusted to it's specific situation. Therefore, one LT can suffer more from vibrations than another. If you connect a vacuum meter to the engine you may see that around 1500 rpm the engine will show little imbalance; at 4000 rpm you probably will see tremendous imbalance. By adjusting the throttle valves (it's a very precise job and this is the part that the BMW dealer is not allowed to do!!) you can put the bike at around 4000 rpm in balance. This is the engine speed that you likely use most. This should only be done by those who have the skills to do so, because you can f*ck up the engine (motronic) big time if you don't know what you're doing.

It's been done to my LT (and many others I know of) and it whirrs like a sewing machine while cruising the highways. It's all smooth now.

I've heard technicians say that the imbalance has consequences for the engine (uneven wear) and most likely up to the rear wheel bearing ....
The screws are sealed with some sort of blue paint. A broken seal will void the warranty (so be sure to have the same blue paint at hand ).

Erwin

R1200GS Adventure LC 2018, Blackstorm/Schieferdunkel Matt/Achatgrau (Triple Black), in full options, BMW Navigator V


R1200GSA LC '18 <- R1200GSA LC '14 <- K1600GTL '12 <- R1200GS Adventure '09 <- K1200GT '07 <- K1200LT '05 <- K1200LT '99 <- K1100LT '95 <- K75RT '92
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post #10 of 10 Old Sep 28th, 2006, 11:46 am
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Throttle Body Synch

Erwin,

Do you have any pictures of the attachment points for the vacuum lines on the throttle bodies themselves? If possible, I would like to see the setup prior to doing work on the bike (hopefully to minimize downtime). Thanks.

Peter Tessin
2002 Champagne
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