Throttle body sync disaster

[dzervit]

I'll make this brief, I mistook the screw pictured below for the old BBS (Big brass screw) on the oilheads. For those that have done a TB sync on the hexheads you know that it's obviously not. After some research apparently its set by the factory and never to be messed with. Oops. I have no idea where it was originally set to, so the question is: Should I just go ahead and replace both throttle bodies or run the risk of impending engine doom?

 

[OoPEZoO]

Nah.....Take a deep breath, you can fix it.

 

Just hook up whatever you are using to balance your throttle bodies and adjust that screw for the best idle you can get without touching the other throttle body. Once it is set, then you can fine tune it with the big brass screw.

 

 

[notacop]

Good call Opeezo!

[bobbobtar]

There are no big brass screws on the '06 1200RT.

[OoPEZoO]

I guess I spoke too soon. I just assumed the newer bikes balanced the same as the oilheads. I haven't had the pleasure of wrenching on a hexhead yet. After a quick refresher, it looks like the computer compensates for the idle balance. All you have to worry about is off idle balance, which is adjusted by the cable length at the throttle body.

 

Your best bet would be not to touch anything else for right now. Then adjust that screw back to the point where both throttle bodies hit the stops at the same time with a synchronous "CLICK". If it is not adjusted correctly, then you will hear two "CLICKS" as one TB hits the stop before the other. If you can get the previously adjusted one back to where it matches the original, then you should be in good enough shape to call it a day.

 

It also sounds like you should do some more reading before you attempt this again. This should help R1200 TBS procedure

[Don_Eilenberger]

It also sounds like you should do some more reading before you attempt this again. This should help R1200 TBS procedure

 

As might: http://www.bmwmoa.org/forum/showthread.php?t=35446 - note the warnings, I tried to make them quite specific.

 

One other thing the OP might try if he has access to a GS-911.. is after getting the clicks to sound the same, use the GS-911 to lock the TB's steppers at the same opening (it's a function) and check the vacuum readings - at idle. IF the valves are adjusted well - they should be the same. If not - a small finesse on the mal-adjusted screw might bring them into line.

 

FWIW - and I tried to emphasise this in the writeup - I have NEVER had to adjust my TB balance on my R1200R - and so far that's in 36,000 miles. Once the valves are adjusted accurately - TB sync falls right in place.

[dzervit]

Dealer was little help. Said to bring it in. I do not have access to a GS-911. I guess I'll get the clicks to sound the same then properly adjust the TB sync as it is off after what I believe to be a very, very good valve adjustment. My TwinMax showed a perfect balance at idle.

 

I just wish someone knew the consequences of moving that screw out of it's perfect factory setting.

[Selden]

I know it's too late for this case, but almost everybody owns a digital camera (even if it's embedded in a cell phone). Take pictures before mucking with something for the first time.

[Matts_12GS]

Nice write up Don!

 

It's bookmarked in my tech file now!

[NewBlue]

Here's my thoughts on this.

You can buy a TB from BMW (expensive) but indicates that they have a standard base flow at CTP and it's not a specific match to your engine.

 

With this in mind if you only adjusted one of the TB's you can match it to the other by building a flow unit of your own.

 

Visit a plumbing store and buy some PVC drain pipe as close to the TB diameter as possible and the rubber boots that join pipe to pipe for repairs. Remove the TB's and either use a Y assembly or a single unit. Install a tee fitting with a ball valve between the TB and the source (shop vac) to bleed off excessive flow, you won't need that much with a closed throttle plate and will keep the vac from overheating and burning up the motor.

 

If you use a Y just match the touched to the untouched TB using a twinmax, manometer, whatever you prefer.

 

If it's a single pipe, install the untouched TB and use a flow meter (the kind used on side-draft carbs) Remove the known good one, install the "touched" and set it the same.

 

The key in all this is to have no air leaks, other then the one through the throttle plate. Park the steppers or remove and plug the holes, same with the injector port.

 

It will require some time and thought but if it's something that keeps you up at night, worth it. After the flow sync the stepper motors and TB off idle sync should take care of the rest.

 

I'm 98.42% sure this will get you pretty damn close to factory as long as you match it to a known good and untouched TB

[Grumpy-ol-Fart]

I had a similar problem with a 1994 RS I bought used. It didn’t have many miles on it, because the previous owner assumed he could maintain the bike himself and had it womperjawed (a fabricated engineering term) so badly it would barely run.

 

The setting being referred to in this post is the positive stop for the throttle butterfly. This establishes the minimum amount of air that can flow through the venture at closed throttle. The adjustments and procedures being referred in this post, are meant to compensate for the fact that no two cylinders are exactly the same, so it is necessary to compensate for these non-uniformities. When the throttle bodies are initially set up, the positive stops are set with a feeler gauge. They are all set at a uniform opening value, you need to get back to this condition in order to fine tune your sync. In order to re-establish a mechanical balance, you need to measure the opening in the throttle body that hasn’t been disturbed and match it on the one you upset. What I found useful for this is a set of numbered drill bits. I just happened to have such an index, if I remember…and this was several years ago, the drill bits I ended up using were in the 60’s range (not a technical verified fact, just a think I remember). I would go to the good TB and open the butterfly and insert a drill bit and release the throttle. If the bit stays in place, do over with a smaller bit until when you release the throttle body, the drill bit won’t stay in place. Then close that drill bit in the bad TB and adjust until the bit just slides out of the venturi. That will put you right at the place you need to be to perform a TB sync and have everything work out all right.

 

It worked for me….

 

[JayW]

...Take pictures before mucking with something for the first time.

 

A good idea in general, but how would that have helped in this situation? You cannot tell from a picture how many revolutions a screw adjustment has been changed.

 

Jay

[dzervit]

Interesting suggestions guys. I like the homebuilt flow meter, that seems like a fun experiment.

 

I'm happy that the bike isn't running poorly or choking at idle. After initially messing with the screw it threw the idle sync off, so I assume that the position it's in now is darn close to the factory as I have a good sync according to my twinmax at idle.

 

I guess since it idles fine and nobody can really tell me what bad things can happen because of this I'm going to just do a TB sync (the correct way) and see what happens.

[Grumpy-ol-Fart]

You can't really tell anything regarding the TB setup by reading the sync at idle, unless you have a 911 and have disabled the steppers. The bike syncs itself at idle.

 

What I described is really necessary if you have disturbed the throttle positive stop, and you have. It isn't really difficult to do. If you do not, then the bike will sync at idle, and you'll have a surge to one side as the engine transitions from the idle circuit to the main circuit. You can sync the main circuit, and the controller will sync the idle circuit; but it won't be right, and probably never as smooth transitioning as it should or could be.

[NewBlue]

You can't really tell anything regarding the TB setup by reading the sync at idle, unless you have a 911 and have disabled the steppers. The bike syncs itself at idle.

 

What I described is really necessary if you have disturbed the throttle positive stop, and you have. It isn't really difficult to do. If you do not, then the bike will sync at idle, and you'll have a surge to one side as the engine transitions from the idle circuit to the main circuit. You can sync the main circuit, and the controller will sync the idle circuit; but it won't be right, and probably never as smooth transitioning as it should or could be.

 

This makes perfect sense ^ Setting with flow can correct a variance between TB's, setting using a wire gauge will get you where you need to be with less effort. At the very least listen to the click(s) when you close the throttle, they should both be heard at the same time. If not adjust the one you varried so they do.

[dzervit]

Snapped, took it to the dealer. They adjusted... seems to be fine. They said no worries. So I won't. And next time I know what not to do.