vibrations

[mig]

Hello all:

Just picked up a 2007 RT with 8,000 miles from So.Cal (Irv Seaver)

I just got home about an hour ago. I had been riding my ST1100 ( 258,000 miles) and knew that this bike would feel diffrent. I know its a thumper. But just a question about cruise vibrations. At3500 RPM the bike feels very smooth ~ 65mph, and when i go to increase the speed to say 75mph or about 4000 RPM the motor get noticably rougher. i increased the RPM to about 5500 Rpm and it felt rough the whole way up. So is this normal or am I out of sync. valves need adjusting? they did a annual inspection ( level 1 check) and brake fluid change. Probably not everything possible. Otherwise am enjoying the new bike. cruise control rocks!!!!

thanks

Miguel

[SWB]

re: So is this normal or am I out of sync. valves need adjusting

 

"Sync" is usually an issue of balance between throttle bodies. The bike has two cylinders and two separate fuel injectors - if they aren't in sync one cylinder will pull harder than the other, resulting in a rougher ride. In extreme cases, the bike may run like and out of tune garbage truck at idle.

 

However, a tune-up includes both valves and TB sync, since you can't get TB sync right if the valves are misadjusted. The third factor on an older bike can be vacuum or intake leaks, i.e. if the bike is getting air from any place other than the throttle body air take tubes (connected to the air box), it'll impact the sync. Other factors I've experienced (on my older R1100RT) was a bad spark plug or plug wire, but that should impact the engine at all speeds.

 

My bike feels smooth through to about 85mph or 90mph, before "normal" activity of a twin at higher revs start causing increased vibrations (in 6th gear). If this is happening sooner, the bike probably needs a tune up. 4000 RPM should be the "sweet spot". 3000 RPM or lower you're probably lugging the bike. 3800 to 4500 rpm is comfortable cruise. Above 4500 RPM and you're kicking it in the pants (but the RT LOVES this - rev it up).

 

The 4cyl bikes will definitely feel smoother in the higher REV bands, but they can have their sync problems too (at least my old Honda 650 did) as long as they have multiple carbs or fuel injectors.

 

Scott

[Motodan]

Yes, to one degree or another this engine, in the 1200RT, will start a more notable vibration in the 4000 to 4200 rpm range (75 mph). It's part of its makeup. I've ridden over 50 of these R1200RT's and everyone of them does this (I sell BMWs). Some are quite mild and hardly noticeable, while others vibrate enough to suggest the injectors are out of sync. If you've had a good service, with a reliable sync job, then this is your bike's "normal".

[dirtrider]

Hi Miguel

 

That 1200RT engine vibration at 4300-4800 RPMs is pretty normal. At that RPM the TB balance or engine tune doesn’t have a lot of effect as the throttle plates are open a fair amount. The farther the throttle plates are open under load the less the delta effects the cross side balance.

 

One of the problems with the BMW boxer is the engine is a 2 cylinder opposed engine and those are basically a balanced engine by design. The problem is due to the rather large cylinders that require a fairly large offset between crankshaft rod journals. The farther apart the connecting rods are the more the engine rocks or vibrates as the individual cylinders fire and try to twist the engine on it’s mounts. This is even more noticeable as the engine is a structural member so is not soft mounted.

 

BMW decided when the 1200 engine came out to complicate it even more by adding a balance shaft to the 1200 engine. That balance shaft contains offset rotating weights to try and calm some of that rocking couple disturbance in the lower/mid RPM “normal” riding or operating ranges. That balance shaft does work at some offending RPMs but seeing as the engine is inherently balanced by design that balance shaft also introduces it’s own imbalance problems in certain RPM ranges.

 

You will probably find your vibration coming is around 4300 RPMs then getting kind of annoying at 4500 RPMs.

 

The good news is it seems to get a little better or at least a little softer as the engine gets more miles and wear on it. I’m really not sure why, maybe as the bike and drive train parts wear in the engine doesn’t have to work so hard to maintain hiway speeds, or the harsh power pulses get a little tamer as the engine gets miles on it, or the rider just gets used to the vibrations, or tire wear changes the rolling circumference slightly, or magic. Most of my 1200 engines have gotten better vibration wise as the miles add up. With your engine only having 8000 miles on it it is still pretty new and tight yet.

 

[Hall Vince]

Some also smooth out with extra miles as mentioned above.

With the two 1200 Boxers I run to 30,000 on each and IMO, they really start to run nicely at 30k.

 

Correctly serviced with all gaps equal and TB in sync.

Ride em hard, use the full rev range, keep an eye on oil level reguarly (if yours uses it) and she'll smooth out given time.

 

I rode a 2010 GS12 last week and thought my 30,000 RT was way smoother.

hth

\v/

[bobbybob]

Yes, to one degree or another this engine, in the 1200RT, will start a more notable vibration in the 4000 to 4200 rpm range (75 mph). It's part of its makeup. I've ridden over 50 of these R1200RT's and everyone of them does this (I sell BMWs). Some are quite mild and hardly noticeable, while others vibrate enough to suggest the injectors are out of sync. If you've had a good service, with a reliable sync job, then this is your bike's "normal".

 

And crash bars will often exacerbate this known vibration. They can set up a harmonic vibe that accentuates it. If you have crash bars, try pressing against them with one or both feet when the vibes start to see if it diminishes. You can feel the change in intensity thru the grips. Had this on both of my RT's. Make sure all crash bar mounting bolts/nuts are tight.

[DaveTheAffable]

Good folks at Irv Seavers. I've been doing business there for about 10 years.

 

There's a fair number of board members in the bay area, and... Francois and Nina are coming to visit! Don't know how they are? Francois, like others here, has done MANY miles on a RT. Just an example of the way folks here get together.

 

Francois and Nina Visit

 

Get with some of the board guys in the area. Look... learn... listen... contribute... and ride the heck out of it!

 

Welcome!