throttle sync DOHC and GS-911

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rclbaker
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throttle sync DOHC and GS-911

Postby rclbaker » Sun Mar 04, 2018 11:36 am

Dear all,

After 120.000 km with my R1200R (DOHC, 2012) and knowing to keep this bike for a long time, I finally bought a wifi GS-911. As many of you already know, it is a marvellous tool and easy to work with.

After searching this forum and especially learning from the many contributions of Don I still have some uncertainty how to check & do a sync. I have a Twinmax as well. But it is not clear to me how to do a correct sync with both tools together.

With respect to hexheads Don suggested some time ago in this forum - based upon experience! - that you can do a sync without using a GS-911. But how do I know that during a sync the steppers are parked? Or that the play in the cables are correct?
Is the procedure for a sync different between hexheads and camheads?

A reference to a kind of a tutorial would also be nice, could not find it on Youtube.

Thanks a lot for any help,

Rob

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Re: throttle sync DOHC and GS-911

Postby hjsbmw » Mon Mar 05, 2018 8:17 pm

I assume it's the same on hex and camhead, but I can't speak with certainty. I have a hexhead.

On the hexhead, one uses the gs-911 to calibrate (or park or whatever the correct term is) the steppers. The gs-911 then tells you to connect your balancer, twin max in your case, start the engine, and do the balance by adjusting the cable on one side.

If with cable play you mean cable slack, then neither tool makes statements about that. I may be misunderstanding you. The cable play is probably stated in the BMW manual, and you'd adjust it according to that.

Hope that helps.
Harald
2007 BMW R1200R

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deilenberger
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Re: throttle sync DOHC and GS-911

Postby deilenberger » Wed Mar 07, 2018 10:12 pm

Hi Rob and Harald - amazing - this forum came back to life for a bit..

My detailed write-up (DIY with pics) lives on the BMW-MOA Forums, in the DIY section of the "hex/camheads". That section is only open to registered members, unfortunately.. but perhaps I can answer a few questions here and give a few clues.

1 - Unless someone has dicked-around (tech-term) with your TB sync - chances are - it's OK. My '07 that I rode to 97,000 miles - never really needed a TB sync. I'd check it - but it never needed it.

2 - Don't even think of checking the TB sync until you adjust the valves - very accurately (I used to shoot for 0.001" accuracy). And once the valves bed in - they tend to not change between checks. I think I actually adjusted them twice during the 97,000 miles, first time at an early service when I retorqued the heads, the second time around 60,000 - and I think they really didn't need it.

3 - The reason I mentioned you really don't need the GS-911 to adjust them is - the air-bypass steppers go into a sync'd mode right off idle. Probably at about 1,000-1,100 RPM. Once they do that - they both are open the same amount. And the function the GS-911 has to zero out the steppers is actually done by the ECU every time you turn the ignition on (put a finger on one of the steppers - you'll feel it) - if you let the instrument cluster do it's entire dance - the zero function has been performed.

4. You ignore the sync at idle. You want to really sync the TB's between 1,200-1,500 RPM - that's where they are most sensitive since the opening in relation to the air-bypass passages (stepper controlled) isn't huge. It's not a small hole (bypass) vs very large hole (throttle opening at > 1,500RPM), it's small hole vs slightly larger hole. If you can get good sync at 1,200-1,500 RPM - then it should be good at higher RPM. I have seen cases where a slight tweak may help a tiny imbalance at higher RPM, but I doubt if you'll ever feel that in the bike.

5. Using the TwinMax is a PITA - but it's what I use too. It's a PITA because it tends to drift around for a while after you turn it on, it eats batteries for lunch, and the potentiometer for adjusting sensitivity isn't a vernier one - it's much too coarse to make a simple balance adjustment. You do want it to be set to "0" at max sensitivity - but that's not easy to do. Keep playing with it - as it stabilizes and you get better at doing it - it's not too awful to do. You obviously do not want the motor running when doing the zeroing out.

6. Make sure at idle BOTH cables have some amount of play in them - enough that you can feel it pulling up at the cable by the throttle bodies. I've seen people really frustrated with how their bike idles - due to adjusting all the play out of one side/cable - so the throttle plate doesn't go to it's stop.. and the steppers really can't compensate for a gross maladjustment like that.

That's it - my clues to happiness doing a TB sync. Hopefully after carefully adjusting the valves you'll check and find like I do - there is no adjustment needed. They did get the cable/junction box right on the R1200R..
Don Eilenberger - NJ Shore
2012 R1200R - I love this bike!

rclbaker
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Re: throttle sync DOHC and GS-911

Postby rclbaker » Thu Mar 08, 2018 5:25 am

Don, Harald,

Thanks a lot for clarifying how to sync. Easier than I thought.
As Don mentioned, no adjustments were needed for the valves according my BMW dealer till 110.000 km.
For the first time I checked the valves by myself and all clearances are between 0,13 - 0,23 (IN) and 0,30 - 0,40 (OUT).
Don, why is this level of accuracy not enough for you? Is BMW too "general" with those limits? Can you notice differences, for instance in vibration or so, when clearances are not `... for 0.001" accuracy?´

I have experience with the Twinmax (and learned to live with...), I used the tool for my R1100RS in earlier years.

Another question, I often read that adjusting for a cable sync should only be done at the right throttle body. Why? I don´t grasp the logic of that.

Regards!

Rob, the Netherlands

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Re: throttle sync DOHC and GS-911

Postby deilenberger » Thu Mar 08, 2018 1:05 pm

Hi Rob - the shims (hemispheres) that BMW offers for the camhead doesn't let you get to that level of accuracy, and I was referring (wrongly) to the hexhead. On the hexheads - I could usually eliminate vibration on someone's bike by getting it to that accuracy or close. There was one forum member who was about to give up on his vibrating hexhead who came, stayed overnight so I could work on a cold engine and left happy the next morning after a valve adjustment and TB sync. In his case - the dealer had done it with the engine hot - and they simply weren't right. It would be nice if we had that option with the camhead - but we don't..

As far as adjusting for sync on the right throttle body - I think that goes back to airhead days - there was something different about the left side carb vs the right side carb that made this necessary, but damned if I can remember what it was. Either side works - just make sure there is free-play in both sides with the throttle closed when done.
Don Eilenberger - NJ Shore
2012 R1200R - I love this bike!


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