2004 Requiring Frequent Throttle Body Synch

[MoonBeemer]

My 2004 is requiring a TB Synch about every 500 miles. Anyone out there got any idea why? thanks Roger

[MIXR]

Roger - One of two things to check, particularly if it's had recent work:

1. Air leaks. Spray something like WD40 around the TBs and see if that changes anything. Also check the blanking plugs for condition as they do deteriorate.
2. The balance system being used. You need to tell us what system you are using and how it is is being used. Twinmax? Manometer? Idle only? At revs? Under load (riding)? Tested by swapping tubes?

All will make a difference. If using a Twinmax, then the sensitivity is also affected by the state of the battery that runs it. Use a fresh battery.

Also check that you haven't unseated one of the throttle cables.

I'll assume your valve end-float clearances are spot-on and that the valves are correctly adjusted.

Failing all that - No idea!

[riceburner]

As said - check for leaks, or loose settings. It could be that the throttle adjuster is coming loose - or the threads on the little rhs throttle adjust have gone - they're only brass, in a steel thead and if the adjuster is left at all loose the threads will wear away. It's happened to me. Fix I have in place (well, more of a bodge), is a small circle of plastic dropped into the brass adjuster which lifts the throttle cable outer about 1 - 1.5 mm. This means the adjuster has to change position relative to the plate it's screwed into, so you're using undamaged threads on the adjuster, not the worn section.

The proper fix is a new throttle cable assembly - which means dismantling half the bike!

[MoonBeemer]

threads on the little rhs throttle adjust have gone - they're only brass, in a steel thead and if the adjuster is left at all loose the threads will wear away.

I have checked pretty thoroughly for air leaks. I had WD 40ed every possible place with no change in RPM. Please explain a bit about the rhs throttle adjust. I am not sure what you mean.

This is driving me buggy. I am using a Twin Max with a fresh battery. Also I make sure the cables are properly seated when I do the balance. I balance the TB at idle with the Big Brass Screws. Then to a 3K rev. However, I have not done the balance with the machine under load. The bad news is that I have had the machine running spot on and it really sucks when it runs like a dog. Well thanks for the input. If anyone else has two cents toss them into the ring. Thanks Roger

[garr2]

Sorry about the dumb questions but these are sort of questions I would ask myself if I couldn't get it right.
What are the symptoms that tell you a TB synch is needed?
When you first attach the Twin Max to the TBs is the synch out at both idle and 3000rpm?
Is it always the same TB that is pulling more vacuum than the other?
Do you check the synch after tightening down the lock nut on the RHS TB?
I've found even this alteration can throw TBs that were in synch a moment ago out of synch once again.
Are the rubber hoses of the Twin Max exactly the same length and in good condition i.e. no perishing or cracks anywhere?
Did you remember to zero the Twin Max before using it?
.

[riceburner]

threads on the little rhs throttle adjust have gone - they're only brass, in a steel thead and if the adjuster is left at all loose the threads will wear away.

I have checked pretty thoroughly for air leaks. I had WD 40ed every possible place with no change in RPM. Please explain a bit about the rhs throttle adjust. I am not sure what you mean.

This is driving me buggy. I am using a Twin Max with a fresh battery. Also I make sure the cables are properly seated when I do the balance. I balance the TB at idle with the Big Brass Screws. Then to a 3K rev. However, I have not done the balance with the machine under load. The bad news is that I have had the machine running spot on and it really sucks when it runs like a dog. Well thanks for the input. If anyone else has two cents toss them into the ring. Thanks Roger

When you do a TB synch you adjust the BBBA screws at idle (this adjusts the tickover and basic balance of the engine), then you need to synch the throttle cables so that they're both turning the throttle butterfly valves in the same way, ie they turn both butterfly valves at the same time.

You balance the throttle cables by adjusting the right hand cable only (leaving the left alone as a datum point). The adjustment is made by changing the position of the small brass knurled fitting on the RH throttle cable, just where it is fitted to the throttle body. this brass fitting is threaded into a steel plate, and has a steel locking nut as well (to keep it from self-adjusting). you check the throttle cable balance by spinning the engine up to around 3K (ie getting it sufficiently out of idle speed), and checking your manifold pressures (using either the TwinMax/Manometer, or whatever*).

The issue you may have is that the threads on the little brass fitting MAY have been damaged by the vibration of the bike. Even if you've not touched it at all. (brass is not the strongest of the alloys.....). unfortunately, the proper fix is replacement of the entire throttle cable system, because the brass fitting is part of the cable assembly and can't be removed without removing the nipple on the end of the cable. If you are happy to remove, and then replace the nipple on the cable, then you could possibly find another brass fitting and do a replacement - but I doubt it would be easy to find one of the brass fittings. I would make an educated guess that BMW won't sell that part by itself, only as part of the assembly.
That said - there's nothing wrong with new cables.....

The "Bodge" fix (for master bodgers only), is to make up a small "C" shaped piece of plastic that's the same outer and inner diameter as the cable outer and bout 1-2 mm thick. This is then dropped into the brass fitting between the brass and the cable outer. The hole in the brass fitting which the cable fits into is approximately 7-8 mm deep (or so), so the cable will still be retained in the hole, you've just adjusted the offset by the thickness of your "C" piece. You then readjust the position of the brass fitting within the steel plate by approximately the same distance (IIRC the fitting has to be screwed INTO the plate, so make sure there is sufficient gap above the steel plate to allow for this - remembering that you need space for the locking nut to move about as well). This will then move the damaged threads out of the steel plate, and you're using "good" threads.
This is NOT a permanent fix though, the thread structure on the brass fitting is now compromised and may well deteriorate further. But as a stop-gap, it works well.

Hope that helps.










* on my old guzzi you could do it by feeling the pressure waves out of the exhausts by hand..... you wouldn't think it was accurate, but it seemed to work!

[R1150Rclean]

Sounds like the same problem I had, previous owner over tightened the lock nut on the right side throttle cable so that the the brass threads were damaged and the throttle cable could not be locked into place. All you have to do is replace the right side throttle cable (~$36), see my posting about 2 months ago on how to do it, takes ~20-30 min. and is not that difficult. Since replacing it I have not done another sync and the engine has been perfect for over 1k miles