Vibes @ 4500 rpm

[Malki]

Hi Folks

I just returned from a 3600 mile tour of 9 Countries in Europe and found the vibration at 4500-5000rpm very irritating. I quite fancied cruising at 90-100mph but had this annoying vibration between 87mph and getting thru it at 103mph. (GPS, not my uncorrected speedo) In day to day use I use this as an upchange indicator as mentioned in earlier posts, but for touring it's a PITA. Just as a matter of interest, my pillion did not feel the vibes.

I've read the earlier posts on Remus exhaust - which I don't want to do, and the exhaust hanger bracket - which was not proved to be the problem.

Just wondering if anybody has a view on the cause of this, or mybe a fix?
Also wondering why BMW have not looked at this obvious problem on later models.

Mine is a 2002 (UK) LT

[dshealey]

Hi Folks

I just returned from a 3600 mile tour of 9 Countries in Europe and found the vibration at 4500-5000rpm very irritating. I quite fancied cruising at 90-100mph but had this annoying vibration between 87mph and getting thru it at 103mph. (GPS, not my uncorrected speedo) In day to day use I use this as an upchange indicator as mentioned in earlier posts, but for touring it's a PITA. Just as a matter of interest, my pillion did not feel the vibes.

I've read the earlier posts on Remus exhaust - which I don't want to do, and the exhaust hanger bracket - which was not proved to be the problem.

Just wondering if anybody has a view on the cause of this, or mybe a fix?
Also wondering why BMW have not looked at this obvious problem on later models.

Mine is a 2002 (UK) LT

Any four cylinder engine without counter rotating balance shafts is going to have a range of vibration, just the nature of the beast. Many small cars with 4 cyl engines do use balance shafts, but that would add weight and bulk to an already heavy motorcycle.

It did not bother me much at all though, I either stayed below 4500 if just cruising along, or down shifted and ran above the buzz range if having fun in the curves.

The old BMW K75 three cylinder engines are much smoother than the four cylinder K engines. The LT is much smoother than the earlier K100's though, so they were able to do something to help smooth it out. Probably tuning of the rubber engine mounts. If you ride at just about any speed and put your foot back on the kickstand arm you will feel that there is a LOT of vibration in the engine/tranny assy that is not transmitted to the frame.

[Malki]

I hear what your saying David, but I do find it annoying on a top of the range bike. Most Jap manufacturers seem the have got this vibe problem out of the way in the late 60's and early 70's on their 4's.

I had the honour of owning a 1969 Honda 750 (K0) single cam inline 4 that never had this problem.

Just can't imagine the owner of a Nissan Micra to a Maybach putting up with this very annoying problem.

You say 'it didn't bother you' but it annoyed the hell out of me, not being able to cruise at speeds I needed to, to get to where I was going.

I love the LT to bits, superb comfy touring machine that will eat country after country, just takes longer to get there than my previous FJR or CBR.

[Daman858]

Malki,

With all due respect, many of us don't worry about the buzz and use it as a shift point. Some have said that removing the exhaust hanger near the skid plate eliminates the buzz. I have no personal knowledge of this.

In your country you can cruise at signifigant higher speed than we here in the US so the buzz might be more of an issue with you.

[messenger13]

If you're in 5th gear, speed up or slow down 5 mph. Or, simply shift into 4th. The vibration range is so narrow, I just don't see the issue. I don't mean to belittle your point, but with time I think you'll find that it isn't as annoying as first perceived.

[Malki]

It's not a big deal, just a little irritating. I certainly don't worry about it causing damage. I've done a good few thousand miles without it bothering me, but when touring the vibes were just where I wanted to cruise at.
Not just a case of moving 5mph it's nearer 20mph before I get thru it. I found myself doing 105mph before I get comfortable with it, and even on the Continent that is liable to get you pulled. Just don't picture me do 400 mile sections of a tour in 4th gear.

As I say, no big deal, just wondered if anybody knew what the cause was.

Upside was I did some miles at 85 and some at 110 :D saved me falling asleep.

[Stobie]

Hey Malki,

I just returned from a week in Europe (including BK Luxembourg Rally) and found exactly the same problem. I agree it can be irritating but you just got to ride through it.

I'm hoping to be at your rally on 2/9 just visiting for the day so watch for the silver LT.

Stobie
Blue Knights
England XII

[alanforn]

I find my wife complains less when I ride @ 4500-5000!

[Sofitel505]

That's the one positive thing the Remus did for me. It eliminated the connection to the gearcase and the buzz was gone. But you trade it for drone and backfires. Take your pick. I guess an industrious guy could install some $0.79 EPDM isolation grommets between the OEM bracket and the housing to see if it would help. Would be a bit cheaper than a $749 header replacement. Live and learn they say.

[Malki]

@ Stobie
See you at Tulliallan - Waggle O' the Kilt Rally

Scottish version of the CCR :D

Hope it didn't rain on you as much as it did on me when over on the other side. I was on the way up from Millau in France on the way to Paris and stopped at a service station because the rain was just torrential..saw an LT doing the same on the other side and we waved...was that you?

[Ted]

Upside was I did some miles at 85 and some at 110

I know the buzz is a bit annoying - but just imagine that your bike is asking you "Are you SURE you want to go faster?" :-)

[Malki]

I know the buzz is a bit annoying - but just imagine that your bike is asking you "Are you SURE you want to go faster?" :-)

For sure Ted, I always said faster...the LT runs sweet at higher speeds.

[humplatch]

I read these threads and wonder if I'm riding the same bike. Vibration this, wobble that. I enjoy the heck out of my LT for what it does well, and every ride brings just more joy. I can't imagine what riders of the other brands have to put up with that I don't. There, I feel better now.:o

[Malki]

I agree that I enjoy my LT and that every ride brings a new experience...so you don't have the vibes and no idea of a fix then ??

[®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 ....

[humplatch]

I agree that I enjoy my LT and that every ride brings a new experience...so you don't have the vibes and no idea of a fix then ??

Yeah, I get some vibration around 4k, but nothing that is annoying unless I just sit in that range. Funny, but about 4200 mine smooths out. Since the speed limit is 65 most everywhere here, I just have to watch for the Highway Patrol a little more. But from there (4200) on up it runs pretty smooth. I got lucky I guess.
I certainly don't have an answer as to how to fix the vibration. I just try to remember how my Kawasaki Mach III, Honda CB750, Honda 305, etc.. performed and count my blessings!!

[Ranger]

After reading this topic yesterday I decided to try the cheap fix of removing the center exhaust hanger. That certainly did the trick, no more distinctive buzz in the 4500 range! It took only a few minutes, one allen wrench from the bike's tool kit, and a 16mm in the socket wrench.

I do wonder about the lack of support though. The exhaust is now supported at the ends only. It would seem the center support is a good idea. Well, I didn't see any reports of this leading to a failure so I guess I'll run it this way for a while.

[hschisler]

...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....Well, THAT is good news. Where does one go to get this mod done, and how much does it cost?

[®win]

Well, THAT is good news. Where does one go to get this mod done, and how much does it cost?
I know of two addresses, but one is in Germany, the other in the Netherlands. Not much help to you.....

How much will it cost? Well, you will have to take off the side panels of the tupperware, the radio stingray, the riders seat with the part of the subframe it is attached to. Once that is done, it's only a small job... :rolleyes:

[meese]

Synching the carbs on the twin Airheads is a pretty common practice, and much easier since the carbs hang out in the open. I used to do the same procedure on my XS11 with four in-line carbs.

A similar procedure can be done to synch the four throttle bodies butterfly valves on the LT, but you do have to remove quite a bit of tupperware first. Few people are aware of this, and I'm not surprised BMW's official response is "don't touch the factory settings".

[bmwrubbercow]

Any four cylinder engine without counter rotating balance shafts is going to have a range of vibration, just the nature of the beast. Many small cars with 4 cyl engines do use balance shafts, but that would add weight and bulk to an already heavy motorcycle.

It did not bother me much at all though, I either stayed below 4500 if just cruising along, or down shifted and ran above the buzz range if having fun in the curves.

The old BMW K75 three cylinder engines are much smoother than the four cylinder K engines. The LT is much smoother than the earlier K100's though, so they were able to do something to help smooth it out. Probably tuning of the rubber engine mounts. If you ride at just about any speed and put your foot back on the kickstand arm you will feel that there is a LOT of vibration in the engine/tranny assy that is not transmitted to the frame.


I agree with all that David said. I had a K100RT and I do have a K75S along with the LT and 3 other bikes.......My LT vibrates at about 5K RPM. I usually avoid that, other than just running through the RPM range, by running in another gear. Will not hurt the bike a bit to run in 4th rather than 5th for extended periods. Will reduce your gas milage somewhat.

[Malki]

Balancing the throttle bodies would seem to be standard part of any major service on any other make of motorcycle.. E.G FJR1300. Maybe there is a little more to it on the LT.
Might just try the easier option of removing the exhaust bracket first and see if that makes a difference. Thanks for all the replies as always.

If not i'll need to return to the Netherlands and get it sorted :D