Sluggish take off

[garr2]

The motor on my 2012 1200 had an annoying habit of being very sluggish when taking off for the first time after a cold start.
Noticeably more revs were needed to get it moving. This went on for about 6 months.
Then I realised that on 3 separate occasions mechanics/tyre fitters had removed the muffler by undoing the bolt that secures it to the frame (at the rear footpeg) and the clamp that secures it to the manifold see clamp 2 below:



So I retorqued the clamp bolt to the specified 28 Nm. It hasn't been sluggish from a cold start since.
Correct torque does more than stop bits falling off!

Ian

[Karamazov]

Ok, I'll bite. How is the mounting clamp affecting performance?

[mogu83]

Ok, I'll bite. How is the mounting clamp affecting performance?

I'm sure it has something to do with the increased torque causing a difference on the ID of the exhaust pipe, this might change the flow patten of the exhaust gas as it enters the muffler producing increased back pressure that could tend to increase torque at lower RPMs. Maybe, but I would have to see dyno print outs from before and after.

But if it worked for Ian - good for him.

[Bob Ain't Stoppin']

Sorry Harry, but that clamp has no ability to change the diameter of a pipe. Thin about squeezing an egg uniformly. Can't break it. Either there is something else going on, or the performance change is all in the mind.

[websterize]

The book says 55 Nm for the clamp on my 2009. If I loosened it to 28 Nm, imagine the possibilities.

[mogu83]

The book says 55 Nm for the clamp on my 2009. If I loosened it to 28 Nm, imagine the possibilities.

Careful Bill. IMHO that could change the flow through the muffler enough that it could be outside the envelope that the ECM can adjust for. Result could be a burned piston or maybe not. Thanks for 'getting it' . I love beemer lists.

[garr2]

The book says 55 Nm for the clamp on my 2009. If I loosened it to 28 Nm, imagine the possibilities

I'm not sure about the 2009 model but for the 2012 R & RT the muffler has to be taken off to remove the wheel.
I'm just not sure every tyre fitter would know the clamp torque (or the wheel torque for that matter) let alone use a torque wrench.

So if someone else mounts your tyres, it possibly already is.

Ian

[dbrick]

Sorry Harry, but that clamp has no ability to change the diameter of a pipe. Thin about squeezing an egg uniformly. Can't break it. Either there is something else going on, or the performance change is all in the mind.

+1

[Karamazov]

Has anyone dyno'd the bike with the clamp completely removed? Seems like there would be some significant weight/hp improvements.

[arp]

Some skeptics here Ian. I guess you need to do a back-to-back before and after test.

The camhead R1200R does have a butterfly valve just upstream of where the muffler clamps on, and the clamp has a marking on it to orient it circumferentially and a seemingly lower torque setting than the prior model. This is shown in the manual. Maybe some how the butterfly valve was being prevented from opening?

[garr2]

... the performance change is all in the mind.

But the voices have always been right before!

Seriously though Alex, you are right about the clamping torque & the alignment with the other clamp on the motor side of the butterfly valve.
The cold start sluggishness may have been caused by a misalignment & a mistorque. I can see an experiment coming up! Can I replicate the sluggishness by deliberately creating a misalignment & a mistorque, and then eliminate it?

A more general point coming out of all this is maybe we should check the fastening torques when others have been working on our bikes.
Exhaust clamp torque is not so critical, but wheel/caliper/axle torques might be worth checking.

Tell me if I'm being too anal.

Ian

[Lost Rider]

If by this logic of the clamp being loose is changing the back pressure or "Flow" dynamics, then how come running aftermarket exhaust doesn't negatively effect a bike? how about those folks not running a pipe at all, like was commonly done on the r1150r.

No way it's that sensitive.

I'm not sure about the camheads, but that clamp has absolutely nothing to do with how my 07' runs. Mine's never seen a torque wrench, and I've even found it very loose after forgetting to tighten it.

Changing the diameter of pipe by a little torque on a clamp or thinking that it can greatly effect how a bike runs is hilarious too.
My bike is always a little sluggish when it first starts, all my bikes start out being a little rough or sluggish when cold, take but a minute to get right.
It's a motor.

If it runs better for Ian by chance after tightening that clamp, great. Maybe butterfly valve dohicky was somehow effected, but all motors run a little rough when cold.

[mogu83]

Ian - Your not being too anal.
It's always a crap shoot when someone else works on your bike. With some luck you will find someone you can trust. In my experience it seems the techs at the BMW dealer live with a torque wrench in their hand, but who knows what happens when your not looking.
As far as tightening the clamp fixing your problem - well shXt happens. If it seems fixed and your happy then have a nice day and ride on. It wouldn't be the first time a problem went away by doing something that had nothing to do with the problem. Don't think about it too much you'll get a headache.

[Karamazov]

It's always a crap shoot when someone else works on your bike. With some luck you will find someone you can trust. In my experience it seems the techs at the BMW dealer live with a torque wrench in their hand, but who knows what happens when your not looking.

+1 on that brother. All skepticism about clamp torques aside, there is some real value to the lesson about other people (even trained technicians) working on your bike. I won't mention specific dealers, as I'm sure it's prevalent throughout, but in my time on motorbikes I've seen the following:

- Chain guard screw forgotten, resulting in a chain guard breaking off while riding... Extremely hazardous
- Oil filler cover left loose, resulting in oil seeping out while riding... Extremely hazardous
- Front radiator screw forgotten, resulting in fan shroud melting to exhaust header... Extremely annoying

In all cases, I failed to do a simple check of the work immediately after picking up the bike, and in each case I realized the error within 50 miles of having service done. Fact is, nobody cares as much about your life and safety as you do, and assuming they do can be a fatal mistake. I now take a few minutes after every service performed by a dealer to go over the bike. I'm also choosing to do more and more service myself. Absolutely nothing wrong with being a little anal, I say keep it up. I'll probably check the torque specs on my exhaust can mount this weekend, just to be on the safe side

[David R]

Every time I start my camhead, the butterfly in the exhaust resets it self to zero. It closes all the way then opens all the way.

IF the clamp was too tight or on the wrong way it could make the butterfly stick in the closed position making the bike sluggish until the pipe warms up and lets the butterfly free.

Does your bike have one of those?

The true job of the butterfly is to change the size of the exhaust for better engine performance. I also think its for quieter exhaust when cruising.

Who knows?

David

[garr2]

Does your bike have one of those?

Yes it does have an exhaust butterfly valve - which is located between the 2 clamps in question.

Ian

[tinytrains]

Proper torque affects the pre-load on the muffler bearing. ---- JUST KIDDING!

[roger l]

If you do have a bad muffler bearing I found a place you can get a new one. The place also offers many other hard to find tools ans accessories.

http://kalecoauto.com/index.php?main_pa ... ucts_id=48


Roger L

[xprof]

Thank you so much, Roger L, for this source for stuff I have been looking for for ever so long! (http://kalecoauto.com) My Blinker Fluid is almost exhausted, my Muffler Bearing is seized up, my Johnson Rod is way beyond replacement hours, and I'm sure the Pilot Wrench will come in handy. Now, where can I score some new Dilithium Crystals for my warp drive?

[dbrick]

Now, where can I score some new Dilithium Crystals for my warp drive?

They're in Aisle 7 at Ace Hardware, next to the elbow grease, left-handed monkey wrenches, and snipe hunt gunny sacks.