Throttle body balancing

Kremmen · Aug 8, 2010

Hi all.
As i had set the throttle bodies on my old R1100s for a number of years, i thought that setting the 1200GS shouldn't be that much different .... oh how wrong i was.
I read the home page sticky to make sure there were no obvious fit falls
Set up my mercury manometers and noted that the right pot was reading 25 Mbar lower than the right. so i slackened the right hand cable adjuster and turned it in a small amount until the two tubes were in perfect alignment.
Removed the manometer and put the bike away.

Next day... when engine got hot she was running lie a bag of nails, so i connected up the manometer once again ... this time to find the R/H pot higher... so i set it once again.. This i thought was strange.
Took it for a run & its still got a very lumpy tick over.

Now when you rev the engine (hot) to about 1500rpm the right hand mercury tube falls away at an alarming rate and is 35 Mbar below the left.... release the throttle and the tubes are level once again.

Before starting i checked the plugs & valve clearances..reset as required.

I'm now beginning to think that it's not as simple as just adjusting a cable and that "electronics" are involved.

Am i missing something in the way I'm trying to set it up
Or is a meter / electronic bit of kit required to be used at the same time of tweaking the cables.

T.REX63 · Aug 8, 2010

Kremmen said:
...
Am i missing something in the way I'm trying to set it up
Or is a meter / electronic bit of kit required to be used at the same time of tweaking the cables.

Yes, the good ole days of "easy" are gone on the 1200's. Now its the stepper motors that need to be synced up. The BMW Service Dep. has a machine for it. Or, you can get one of those handy GS-911 devices and do it yourself.

Best of luck!

Magwych · Aug 8, 2010

Or you could sync at 4,000 RPM ...

Below that the the stepper motors try to keep the throttles in line, if you adjust the cables without first parking the stepper motors, the steppers will undo all your hard work.

Before the GS-911 provided the ability to park the motors, I synced with the motor at 4,000 rpm, an that seemed to work fine. There is at least one thread in the 12000GS section about this. IIRC it contains a link off to a thread on advrider.com that explains all.

T.REX63 · Aug 8, 2010

Magwych said:
...
IIRC it contains a link off to a thread on advrider.com that explains all.

You're probably referring to this one from Jim van Baden?

Cheers,

Kremmen · Aug 9, 2010

Many Thanks guys for your input.
I've decided to purchase a GS911 when i get paid this month.
I've been checking out what it does & the online product upgrading sound really good.

As i don't have one of those large fans & revving the engine not under load to 4000RPM i feel is potentially asking for the valves to kiss the pistons.

Regards

T.REX63 · Aug 9, 2010

Kremmen said:
...
As i don't have one of those large fans & revving the engine not under load to 4000RPM i feel is potentially asking for the valves to kiss the pistons.

Regards

Well, I've done the adjustments on a cool Saturday morning, riding the bike up to temp and doing the checking/adjustments in a business park. If you don't take too much time, you can get away without needing a fan. Also, 4,000 rpm will not do any harm. Just keep an eye on the engine temperature.

The "business park" is only needed to maintain good relations with your neighbors at home...

littleredrooster · Aug 11, 2010

Kremmen said:
..... & revving the engine not under load to 4000RPM i feel is potentially asking for the valves to kiss the pistons.

Regards

The valves cannot kiss the pistons at 4000rpm either under load or not under load, makes no difference. Open the throttle fully and let the rev-limiter do its job if you're brave - it won't explode, only sound a bit alarming. Go to any GP race campsite and listen to this happening all night long......

The danger from revving an unloaded engine used to be from high torsional reversing loads on the crank/rods, but modern engine design has all but sorted this.