loud tapping, seems to be throttle pulley

[22893]

After replacing the HES and fuel filter on my r1100rt I noticed a loud tapping that I had not noticed before (possible it was there before and I didn't notice).

The sounds stops when I put my finger on the right side throttle pulley. Left makes no noise. I've attached a pic of the "pulley". At least some of the sound is coming where this "pulley" is vibration against the adjustment screw (where arrow points).

Anyone encountered this vibration before and any ideas of what is causing it? It's surprisingly loud.

(I apologize for having so many silly questions).

 

[22893]

The loud tapping sounds kind of like this video, although I don't have the visible bouncing of the "pulley" as shown in the video.

Only 30k miles on motor so hopefully not worn out.

Is a fair bit of tapping at the throttle body normal?


https://www.youtube.com/watch?v=QV9Vv01S0EU

 

[m_stock10506]

Do a valve adjustment/check and then a throttle body sync - then tell us if the tapping is still there.

 

[lowndes]

Too much throttle cable slack

Try adjusting out the throttle cable slack on that side. Might as well get a Twinmax or a Carbmate to balance the TB's at idle and just off idle, then at 3500-4000 rpm, THEN take the slack out.

 

[22893]

Try adjusting out the throttle cable slack on that side. Might as well get a Twinmax or a Carbmate to balance the TB's at idle and just off idle, then at 3500-4000 rpm, THEN take the slack out.

I adjusted the valves not too long ago and today used my carbmate to check idle balance (ok) and set just off idle and higher. Was a bit off and is now pretty close. Sound seems the same.

What do you mean, take out the slack?

 

[PGlaves]

You will find a worn throttle shaft. The throttle body needs to be rebuilt. Bing has the kits to do it, or they will do it for you.

 

[happy wanderer]

Good throttle body repair kits and how to's on ADVRider here: http://advrider.com/index.php?threads/r-1100-1150-gs-rt-rs-r-s-throttle-body-repair-kit.630335/


Dan Cata makes some nice stuff.

 

[cycleman2]

That noise is pretty normal on oilheads. As the shaft wears it will get worse and if you have a vacuum leak in the shaft area then you have to replace. You will only hear the noise at idle because once you take up the slack ( turn the throttle ) the noise goes away. As you always need a very small amount of slack at idle there is really no way to make the noise go away. What is going on is, there are intake air pulses as the cylinder is going up and down, drawing air into the cylinder to mix with gas, and as the throttle plate is in this air stream floating so to speak, it bounces back and forth which over time wears the shaft, resulting in the noise.

The finger test you made is the way to tell if that is the problem. As you found it takes very little pressure to change the noise or to affect the running of the bike.

So if you don't have a vacuum leak at the shaft keep on riding. This is one of those things to put on your to do list in the off riding season.

 

[22893]

That noise is pretty normal on oilheads. As the shaft wears it will get worse and if you have a vacuum leak in the shaft area then you have to replace. You will only hear the noise at idle because once you take up the slack ( turn the throttle ) the noise goes away. As you always need a very small amount of slack at idle there is really no way to make the noise go away. What is going on is, there are intake air pulses as the cylinder is going up and down, drawing air into the cylinder to mix with gas, and as the throttle plate is in this air stream floating so to speak, it bounces back and forth which over time wears the shaft, resulting in the noise.

The finger test you made is the way to tell if that is the problem. As you found it takes very little pressure to change the noise or to affect the running of the bike.

So if you don't have a vacuum leak at the shaft keep on riding. This is one of those things to put on your to do list in the off riding season.

What's the easiest way to tell if I have an actual vacuum leak at that throttle body? Spray a little starter fluid or carb cleaner at the area at idle and see if rpm changes?

 

[bikerfish1100]

your throttle shaft is worn. replace is the fix. Beemer Boneyard sells the Dan Cata kits. Less than Bings.
http://www.beemerboneyard.com/nsear...one=http://www.beemerboneyard.com/thboin.html

 

[bikerfish1100]

What's the easiest way to tell if I have an actual vacuum leak at that throttle body? Spray a little starter fluid or carb cleaner at the area at idle and see if rpm changes?

that would work.

 

[happy wanderer]

What's the easiest way to tell if I have an actual vacuum leak at that throttle body? Spray a little starter fluid or carb cleaner at the area at idle and see if rpm changes?

Yep, that should work. Interesting comments on pulley chatter. Mine chatter when I don't leave enough free play in the lower cables. Carb cleaner, brake cleaner, WD40... do not use silicone spray whatever you do though. It will wreck the O2 sensor in a hurry.

BMW service manual is pretty clear on cable clearance and I would check them carefully before anything else. If you have an early 1100RT without the Bowden box and one long throttle cable that wraps around the left side TB which continues over and terminates on the right side the procedure is different and more tricky to get just right.

 

[cycleman2]

What's the easiest way to tell if I have an actual vacuum leak at that throttle body? Spray a little starter fluid or carb cleaner at the area at idle and see if rpm changes?

There are a few different ways but the least messy that I've used involves using a small ( UNLIT) propane cylinder. Have the engine running and pass the tip of the OPEN & UNLIT cylinder in and around the throttle body shaft. If the idle increases you have a vacuum leak. You can also use this method to check out intake/carb boats etc.

When you adjust the cables for the required slack, that is a baseline and allows you enough slack to do a sync. When you do a carb/throttle body sync you use up some of this slack ( normally on the left side ) so that you can get both cables pulling equally. There is nothing magical about the process and it is the same procedure with carbed airheads. One thing to make sure is that the choke or enrichment cable isn't affecting your idle. Its very easy to have this adjusted so that it affects the idle. It is easy to check, once the engine is warmed up and the idle is steady in the 1100 rpm range, then slowly shorten the cable until it speeds up the idle, then back it off until it doesn't affect the idle. This will usually help a great deal in getting the enrichment set properly to help with cold starts.

 

[22893]

Current status is I adjust more slack in the throttle cables and the sound pretty much is gone at least for the moment.

I did wave an unlit propane torch around both sides of the TBs and had no rpm change.

For now I'll just ride it and focus on other things.

 

[happy wanderer]

Current status is I adjust more slack in the throttle cables and the sound pretty much is gone at least for the moment.

I did wave an unlit propane torch around both sides of the TBs and had no rpm change.

For now I'll just ride it and focus on other things.

If that's the case then throttle cable adjustment is your problem, not a vacuum leak and not the throttle shaft bushings. When the bushings are bad enough that they need replacing you can just grab the pulley and wiggle it up and down. If there is more than just a tiny bit of free play there you should think about doing the bushings over the winter. In the meantime, synchronise them after a proper valve adjustment taking care that you have enough free play as per the manual page I posted above and ride it.