Throttle Body Assembly Question

[jgrm1]

When twisting the throttle grip just enough to take the slack out the throttle cables, I get a clattering from the right throttle body. The clattering goes away with RPM, but does not sound cool. She's been doing this for some time.

I just performed the 36K service and the throttle bodies are synced about as good as humanly possible. While performing the sync, I played with extremes of the right hand throttle cable adjustment to see if it affected the clattering. It did, but only to make it worse, not to make it go away.

Poking around some more, I noticed the throttle cable cam on the right-hand throttle body has some side-to-side play in it that the left-hand body does not. When using my finger to "load" the shaft this cam rides on, I was able to reduce the clatter.

Is it possible to tighten up the throttle body assembly to eliminate this play and related clatter?

Thanks,
Jeff

[shovelstrokeed]

No real adjustment available. There are bushings in the body, with seals, that support the throttle shafts and they can get worn. The clatter you are hearing is likely because the stop screw has worn the tab it bears against a bit and now the throttle plate is hitting the body.

A check might show by how much the large brass bypass screws are backed out to get the idle at 1000-1100 RPM. They should be right around 1.5 turns. If more by any appreciable amount, you have probably found the problem. Despite BMW's dire warnings, you can adjust the throttle stop screw. It'll take some trial and error to get it all right again. There is an article on the IBMWR site by Rob Lentini about a procedure called zero=zero that will be helpful. The primary difference being that you will have to reset your Motronic differently.
Key off - pull f$ for 1 minute and replace - key on but don't start - open and close throttle 100% 2X.

This is worth a try as the throttle bodies are quite expensive.

[BMW Atlanta]

when was the last time you replaced all of the throttle cables including bowden box contraption?

[jgrm1]

Never replaced the cables. She now has 36K miles. Could this be the culprit? The action feels smooth from the grip. Plus, I thought the reason for the sync was to accomodate cable stretch.

-Jeff

[BMW Atlanta]

You definitely need cables if youre complaining about anything relating to the throttle bodies at that mileage. The Bowden box has 2 plastic pulleys,....one for each TB cable and they will wear independantly of each other. Therefore therefore it will be hard to get a good sync across the rpm range. You will have to do with good on the bottom or good in the middle, etc instead of a good sync throughout the range. I replaced mine at 18k because I'm anal like that and it was apart anyway.

[brad black]

the throttle shaft bushes can wear, leading to what you're talking about. we've had quite a few rebushed by carb repair shops - works well.

[JonyRR]

Hey Brad; could you elaborate about the mechanical rebuild? The carb place...they disassembled the shaft and butterfly and physically replaced the bushings? Wow...then it IS possible. That means if one can do it, someone else can also. Good info to know.

[roger albert]

Of course it's possible. Done on old carbs, especially Webers, all the time. We just seem to have relatively few old school places that do that work regularly enough to make it _economically_ doable. I had a shop that would do it for a couple hundred, but I'd rather just buy a new one at that.

Still, I haven't seen those bushings be a problem with the relatively low miles Jeff has stated. Seems odd. Guess anything is possible.

[JonyRR]

Hmmmm....I have 46MM webers from my 911 apart (so cool to have actual removable venturis and man are those weber castings a work of the foundry-maker's art) on the bench at the moment. I'll have to look and see how the bushing setup is. I have heard that the TB's wear the butterfly shaft bushings out at roughly 50K miles. It's nice to know I shouold be able tor ebuild them instead of buying new assemblies (I HATE assemblies VS repair parts).
Supposedly BBPower bores these tb's somewhat oversize; one would assume the shafts and butterflys come out for this operation and a new, larger butterfly is manufactured to fit the bigger bore (I think they're claiming like a 3MM size increase)

[roger albert]

Yeah, should be doable. Nice pieces, those old Webers.

Back on mileage, I have dozens of customers with mileages much higher than 50k and absolutely no such rattling. 50k service life is selling them WAY short. That's just about the lower limit (maybe Jeff is the new low???) I have a good number of guys at > twice that mileage and no problems or rattles even.

[JonyRR]

and that's good to hear, roger. One of the main reasons I stepped up (or stepped over, depending on point of view) to BMW was the longevity aspect. When I cut the cashier's check for my S, I said to myself 'hmm, better really like this thing, it's gonna be around at least 10 years'. then came the learning curve bay-um-vay VS the japsikkle way of d0ing things. I think I'm about flattened out on that curve....I hope
I've been looking for a dead oilhead so I could yank the engine down to it's shorts and get some experience inside the cases of same. (I want something closer than joe's east-coast basketcase) an R1200C would be ideal...maybe one that's a total/fire damage...

[roger albert]

Looking for same here. Need closer too.

[JonyRR]

so a crank from an R1200C, with the 1136CC cylinders and 1100 rods is supposed to make a 'long-rod 1200', or so I hear. That's what I''m looking for. the stroked crank, the 1136 barrels, use 1100 rods and (if they don't exist) ross or venolia pistons with the pin location for the (longer 1100) rods in 12:1 CR. Or that's the rumor/bs anyway.

[jgrm1]

Originally posted by roger albert
(maybe Jeff is the new low???)

Hey, I resent that remark!

-Jeff

[imintman]

Getting back to the TB...mine (right side-the cheap one) was clacking loudly at just above idle (slight throttle pull). The dealer replaced it under warranty. No cables were replaced. The new one doesn't make a sound. Bike is an '04 R1150RS with 14k.