throttle body synch questions

[TowJam]

Apologies in advance for what is obviously some noob questions...

 

Is the TBS something specific to BMW bikes? (I don't recall this being a service issue with my previous Honda and HD bikes.) What is the recommended maintenance interval? Is it necessary for both the R and K engines? Other than poor performance, is there any possibility of longer term engine damage if the TBS is not performed regularly?

[gefish]

Throttle body synching is required on any engine with multiple throttle bodies. Stock Harley's have only one throttle body. It is a little more important on boxers due to the throttle bodies being separate rather than ganged together as on most Japanese fours or BMW K-bikes. The body to body linkage in a four cylinder arrangement is much more rigid and alignment easier to maintain. On separate bodies with individual cables pulling the bodies open, cable streach and wear make a much larger difference. It makes a significant impact on power and smoothness with any bike and should be checked at regular intervals.

[Ken H.]

Any multiple carburetor or multiple throttle body equipped engine requires synchronization.

[JohnJC]

Like above, needs to be done.

 

I just check/adjusted the TB's on my R12st at 3k miles. They were done by the dealer at 600 miles, but I started noticing more vibs. It was the TB sync. Smoothed things right up. Not surprised, bikes do a lot of breaking-in the first several K miles.

 

My other bikes didn't vary much after the first couple of services, but this is my first BMW so I can't comment on the long term. I can tell you the little bit they were out of sync added more vibs than I've experienced on other bikes(even other twins).

[Joe_Rocket]

JohnJC... can you outline how you synchronized the throttle bodies? I'd like to do it on my R1200RT myself.

 

Joe

[Bugs]

Mine had to be adjusted at my R12RT's 600 mile.

 

Also just had a 4K done on my '04 Yamaha R1 and, according to the mechanic, they were way out of sync. The adjustment made a huge improvement in performance.

[Ken H.]

JohnJC... can you outline how you synchronized the throttle bodies?

Yes, please do so. To my knowledge no one has come up with an after-market way to park the stepper motors on the new R1200xx hexheads. A necessary part of doing a sync on them. So I too am curious how you did it.

[JohnJC]

Yes, please do so. To my knowledge no one has come up with an after-market way to park the stepper motors on the new R1200xx hexheads. A necessary part of doing a sync on them. So I too am curious how you did it.

 

Hmmm. Never heard of such a thing, so maybe what I did was wrong. I was able to get my gauge to balance, and it did improve the vibs & throttle response noticeably. So, you may want to ignore the rest of this post.

 

I used a Carbtune, http://www.carbtune.com/ fo\r my sync guage.

 

The bike up to running temp. I attached the gauge to each throttle body at the vacuum port to the outside of the TBs. On the right it had a vacuum cap. On the left a vacuum line ran to the same point, I just pulled it and attached my gauge.

 

The Sync was pretty close at idle. Between 3k and 4k rpms balance was off just over 2 (what ever units Carbtune uses).

 

On all my other bikes I'm use to finding an adjustment screw on all but one of the TBs. Didn't see any such beast on my R12ST so I used the cable adjustment on the right hand TB. I did this while holding the throttle at just under 4k rpms.

 

Once finished, the balance is slightly off at idle(I'm mean VERY little). Once off idle it holds even up through 5k rpms(I didn't rev it any higher).

 

It took me two tries to get it right. The first time the bike got VERY warm while adjusting. On the road I found it to feel pretty good in the upper range, but didn't like the lower range. Vibs and response were off. The next sync attempt I was a lot quicker and completed it while the bike was still at a normal operating temp. Now it feels great.

[Ben Peeples]

Adjust your valves first. A small difference between cylinders in the valve adjustment will make a huge difference in smoothness of the engine. Ben.

[JohnJC]

I think the valves were checked/adjusted at the 600, and I'll take it in for the 6k. The valves may be off but, I was just doing something external and simple between the scheduled maint. It made a difference.

[CMWingfield]

Hi Ken,

 

Could you elaborate on the Stepper Motors you mentioned in your previous post? I've never heard of them and I was intending to do my own service just like on my 1150.

 

Thanks,

Mike

[Marty Hill]

Just a second! Many of us ignore the stepper motors, the idle is spot on. I've just done my 30k. Valves first then adjust at 3.5 to 4k. Bike runs great and has all along. Make believe it's an 1150/all is the same. If idle is screwed up/see the dealer/if not DIY!

[CMWingfield]

Thanks Marty. I understand now.

Mike

[Marty Hill]

Mike,

 

You are gonna love not taking off the tupperware.

[Ken H.]

Could you elaborate on the Stepper Motors you mentioned in your previous post?

Remember the air bypass screws on the older oil heads, commonly referred to the Large Brass Screws (LBS)? The R1200xx doesn't have them. It has air bypass passages that are controlled by the engine management computer by small stepper motors, one on each TB. These are used to adjust the sync on the fly.

 

Now how much these affect a DIY sync is a matter of some debate. Can we just pretend they are not there? Experience with the LBSs on the older oilheads would indicate no. The LBS positions would affect sync at any RPM range, why would we think the position of the stepper motors would not?

 

The factory procedure has the dealer, using their diag. equipment, "park" the steppers in a pre-determined position prior to adjusting the cables for off-idle sync. We presume (but don't know for sure) they are centered in their range when parked so as to give maximum +/- auto-adjustment range. When you do a sync without taking this into account, you may or may not end up within a usable range and may or may not end up with a bike that is smooth through out its RPM range.

 

I've experimented with off-idle sync both with and without the stepper motors connected and there is a definite difference. Neither is the right way though I believe. What we have yet to learn is how to correctly park/postion the steppers without a $40K BMW testing machine!

[Marty Hill]

Ken,

 

I'm no expert but I've done my bike 5 times and about 9 other bikes including 2 that had just come from the dealer that weren't running very well. All were/are fine and running better than when returned from the dealer.

 

Could this just be blind luck? Yes, but it seems to work for me.

[Ken H.]

Did you leave the steppers connected, or disconnect them when doing the above idle sync.?

[Marty Hill]

Ken,

 

I never touched them. Maybe I'm just lucky.

[DouglasR]

The latest issue of BMW MOA Owner's News has a great step-by-step article on this subject using a Twinmax....

 

Great magazine!

[codinn]

The latest issue of BMW MOA Owner's News has a great step-by-step article on this subject using a Twinmax....

 

Great magazine!

 

Here's some CPR on an old thread:

 

I don't have the BMW MOA Owner's news. Would anyone care to summarize the article here?

 

I mean, can you do this job at home properly with a Twinmax or not?

 

If so, what is the secret to getting around the stepper motor issue?

[Ken H.]

The article addressed the pre-stepper motor throttle bodies only.

[STUFF2C]

These are the easiest ever. Just get the bike up to temp and adjust the Right side only. Done. KISS!

[codinn]

These are the easiest ever. Just get the bike up to temp and adjust the Right side only. Done. KISS!

 

KISS, eh? That is just about enough information to get me in some real trouble. Would you care to provide a tad more detail such as RPMs and why this is so simple given the seeming disagreement earlier in the thread? What am I missing here?

[ShovelStrokeEd]

Co,

What you are missing is you can only do the high speed sync with the TwinMax. Unless you have access to the factory computer system to Park the idle air bypass motors, you will chase that adjustment forever as the motors compensate for your adjustment.

 

I'm not sure how the system works at idle exactly. I would kinda bet on its chasing the TPS signal from each throttle body, those having been preset at the factory to represent a throttle blade opening that gives a certain air flow rate.

Idle air bypass motors strive to match both TPS and RPM criteria.

[codinn]

Co,

What you are missing is you can only do the high speed sync with the TwinMax. Unless you have access to the factory computer system to Park the idle air bypass motors, you will chase that adjustment forever as the motors compensate for your adjustment.

 

I'm not sure how the system works at idle exactly. I would kinda bet on its chasing the TPS signal from each throttle body, those having been preset at the factory to represent a throttle blade opening that gives a certain air flow rate.

Idle air bypass motors strive to match both TPS and RPM criteria.

 

Ken, Jerry and Ed,

 

Thanks for filling in the missing pieces, guys. I'll just make the assumption that things are peachy at idle for now and do the high speed synch only.

[Marty Hill]

Yeah, that's what I said quite a while back.

[Ken H.]

Yeah, but it still bugs me that we don't know how to park the steppers ourself so has to have a definitive starting point.

[codinn]

Yeah, that's what I said quite a while back.

 

Marty, don't you realize some of us LIKE to hit ourselves in the head with a hammer?

[STUFF2C]

Twin Max? nah. See Pic. I don't remember where I got it, but it works great for twins.

[Marty Hill]

Ken,

 

There is an old saying...don't worry about thinks you can't change...or something like that. Go ride!

 

The bike will be fine.

[codinn]

Twin Max? nah. See Pic. I don't remember where I got it, but it works great for twins.

 

Jerry,

 

Is the -15/0/+15 good or would a more sensitive gauge be better?

 

I found -10/0/+10 and -5/0/+5 inches of water magnehelic gauges as well as the -15/0/+15.