R1200ST engine stumbles on roll on.

[Bud F]

My ST runs and pulls very well and is great if I ease the throttle up. But try a quicker roll on (to move out to pass

at highway speed and the engine stutters and coughs.

This condition, I suspect,must be caused by a faulty sensor

of intake vacuum (if such a thing exists)

Comments anyone ?

Cheers

Bud F

[motoguy128]

I suppose it could just be a loose connetor on the MAP (Manifold absolute pressure) sensor or the throttle postion sensor. The dealer could diagnoise it immediatly.

 

It's also possible you're being too aggressive with the throttle.... but not liekly. I rarely snap the throttle open quickly because I'm used to riding with a passenger. I roll on assertively but progressivly even when passing.

[ShovelStrokeEd]

What RPM? If you are below 3000 RPM when this happens I would more or less say it is to be expected. In the higher gears it might happen at even higher revs.

 

I don't think the 1200 has a manifold air pressure sensor(s). Could be the throttle position switch is faulty, bad connection or maladjusted. Simple test by your dealer as it should throw a fault code.

[Satguy]

Change the main spark plugs.... There is no vacuum sensor to become faulty.

 

Have seen a few 1200s that fall flat and changing the plugs fixed 'em

 

Good Luck

 

[Bud F]

Thanks, Satguy, I,ll try changing the two main plugs.

It seems strange though, that if the roll on is slow,

the engine pulls hard and will rev. high in top gear at

highway speed.

 

Bud F

R1200ST

Kingston ON.

[Mike_in_WI]

I had what sounds like the exact same problem with my '05 RT. It was a spark plug...

[Satguy]

It seems strange though, that if the roll on is slow,....

 

Yep, that is what I thought too. Changed the plugs and bike ran correctly.

 

 

[Bud F]

Thanks a bunch Bruce for your tip.

As you say it doesn't figure, but I replaced the two main

plugs. And low and behold --- no more stutter.

Great, that saves me a hundred mile trip to the dealer.

The plugs that came out looked clean and normal --- so

if anyone knows why , I,m curious to know.

cheers

Bud

[Satguy]

Hi Bud:

 

The old plugs that you took out were Bosch right??

 

And the new ones are NGK?

 

For some reason, BMW switched from the Bosch to the NGK plugs for the R1200 engines. I don't know why, but there was obviously some problem with the Bosch plugs.

 

Glad the bike runs better now.

 

[Bud F]

Bruce

Yes, you're quite right, the plugs I took out (only the two main

ones) were original Bosch and looked very good.

But they misfired under quick acceleraion.

Now the replacement NGK cannot be made to misfire.

Very funny.

Guess I'll leave the secondary plugs in as long as the

engine runs well. I did buy two more plugs from the dealer

at their rediculous price for backup.

Thanke again.

Bud

R1200ST