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TwinMax tuning/stepper motors


RoSPA_man

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Hi

I do all my own servicing etc (R1200RT) and I only resort to the dealer for warranty work. I use the Twinmax to balance the cylinders regularly and I have no specific problem – bike seems to be running sweetly and compares well with any others that I ride.

 

But the role of the stepper motors always bugs me a bit. I’m not certain of their precise role and I have read the various post and opinions as to the effect they have. I have tried tuning with them in place and with them disconnected and it seems to make no discernible difference. Typically I adjust balance with the steppers connected, the re-check, then a final session with them disconnected.

 

I have several questions

1. Do the stepper motors play a continuous role at all RPMs or are they just tick-over related? In fact, if they do play a magic role at all RPMs in maintaining balance, then why bother balancing at all?

2. Has anyone got an opinion on whether the fancy gadgetry/diagnostics at the dealership can/does result in a better balanced bike or would I just be wasting money having the dealer tune the throttles?

3. My tickover is never balanced and I believe that is either designed in, or not adjustable? Can anyone confirm their take on this – I think the tickover is biased to the left cylinder a little. The purist in me would love to arrive at a balanced tick-over AND also be balanced through the rev range.

 

In a nutshell, is a dealer tuneup likely to beat my own!

 

Any thoughts would be appreciated

 

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Good questions! I am not fully sure of the role of the steppers either, but I believe that they are mostly active at low RPMs and at start up holding open the throttle a bit to m ake up for cold starts and such that is why the suggestion is to unplug them before doing a TB synch. As far as the fancy computer/diagnostic thingy at the stealership according to the service manager/head tech at my local it turns off the steppers in the bikes control circuits and then acts like a manometer/twin max for the tech to set the range. I am not sure about the fancy gadgets doing any better of a job than you or I with or comparatively stone age tools, especialy when you take into account that we are more likely to be quite anal retentive about getting things as close as we can, with out worrying about time and getting to that next job. I think you are right about the balance being weighted to the left considering that the service cd says to only adjust the right throttle body cable and using a twin max it is really difficult to get a good read at idle speed with that indicator needle flying around side to side. I feel that at least for the bottom range a manometer is easier and possibly more accurate, while the twin max is great for actual under load (riding) testing and adjustment due to the mercury tubes not being very portable.

I also would love to hear from someone with more experiance working on BMWs than myself about this. If you have HD questions I can give qualified advice and help but I'm pretty new to the flat twins myself.

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From my understanding, the new GS-911 beta software due sometime later this month is supposed to help stop the steeper motors so that a tech can adjust the idle.

 

 

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using a twin max it is really difficult to get a good read at idle speed with that indicator needle flying around side to side.

 

If it's doing that then it's likely that you're not using vacuum restrictors like these . They fit inside the vacuum tubes and will help drastically whether using a manometer, gauges or twin max.

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using a twin max it is really difficult to get a good read at idle speed with that indicator needle flying around

 

If that needle is flying around at idle I need to ask if you have read the instructions on how to use it...?

 

Mine does not do that.

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using a twin max it is really difficult to get a good read at idle speed with that indicator needle flying around side to side.

 

If it's doing that then it's likely that you're not using vacuum restrictors like these . They fit inside the vacuum tubes and will help drastically whether using a manometer, gauges or twin max.

 

Is the function of these restrictors just to desensitise the measuring gauge- in the case of teh Twinmax, there is a sensitivity dial switch, which would appear to do the same job, or am I missing something?

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I’ve walked through this here before, so this will be a quick version. If you want more detail, search for my older posts on the steppers.

 

The steppers adjust the amount of bypass airflow in the TBs at all RPMs. At idle they track independently in an attempt to improve idle especially on a cold engine. E.g. – One may be at position 108 the other at position 177. (Actual numbers from my bike BTW.) Not always with complete success, as we know by monitoring idle sync. But who rides at idle?

 

As the engine warms, at idle they gravitate toward each other as measured engine parameters dictate.

 

However, as soon as the throttle is moved off idle they move to a matched position and track together. E.g – 150 & 150 at 2000RPM, 141 & 141 at 4000RPM, etc.

 

So what does this mean for doing our own TB sync? It means because we always sync a hexhead at some RPM above idle, we can effectively and with confidence leave them connected and ignore them.

 

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Thanks Ken.......Answered one of my questions as my 12RT idles a little rough when first started and I was wondering about it as I did a throttle sync just recently.......Seems to be fine after warmed up....

I did go out, turn the key on and rotate the throttle to the stop a couple of times just to be sure that it has programmed itself........

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using a twin max it is really difficult to get a good read at idle speed with that indicator needle flying around side to side.

 

If it's doing that then it's likely that you're not using vacuum restrictors like these . They fit inside the vacuum tubes and will help drastically whether using a manometer, gauges or twin max.

 

Is the function of these restrictors just to desensitise the measuring gauge- in the case of teh Twinmax, there is a sensitivity dial switch, which would appear to do the same job, or am I missing something?

 

Yeah, pretty much.

 

 

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Just for the record...

I was a doubter when Twisty1 mentioned doing a cold start with the RT's throttle open a little.

 

I can testify the cold start was immediate and convincing. He rules!

 

As for the OP... let me also make it simple. The instructions say to turn the sensitivity to maximum LOW at the start up, otherwise you will risk damage to the Twin MAX and you will not be able to read it anyway.

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I’ve walked through this here before, so this will be a quick version. If you want more detail, search for my older posts on the steppers.

 

The steppers adjust the amount of bypass airflow in the TBs at all RPMs. At idle they track independently in an attempt to improve idle especially on a cold engine. E.g. – One may be at position 108 the other at position 177. (Actual numbers from my bike BTW.) Not always with complete success, as we know by monitoring idle sync. But who rides at idle?

 

As the engine warms, at idle they gravitate toward each other as measured engine parameters dictate.

 

However, as soon as the throttle is moved off idle they move to a matched position and track together. E.g – 150 & 150 at 2000RPM, 141 & 141 at 4000RPM, etc.

 

So what does this mean for doing our own TB sync? It means because we always sync a hexhead at some RPM above idle, we can effectively and with confidence leave them connected and ignore them.

 

Thanks Ken - useful reply!

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I’ve walked through this here before, so this will be a quick version. If you want more detail, search for my older posts on the steppers.

 

The steppers adjust the amount of bypass airflow in the TBs at all RPMs. At idle they track independently in an attempt to improve idle especially on a cold engine. E.g. – One may be at position 108 the other at position 177. (Actual numbers from my bike BTW.) Not always with complete success, as we know by monitoring idle sync. But who rides at idle?

 

As the engine warms, at idle they gravitate toward each other as measured engine parameters dictate.

 

However, as soon as the throttle is moved off idle they move to a matched position and track together. E.g – 150 & 150 at 2000RPM, 141 & 141 at 4000RPM, etc.

 

So what does this mean for doing our own TB sync? It means because we always sync a hexhead at some RPM above idle, we can effectively and with confidence leave them connected and ignore them.

 

Nice summary - thanks for the clarification

 

 

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Officially BMW says just above idle. E.g. – 1500 RPM or so.

 

Others prefer to do it at their most common riding RPM. 3500 or whatever.

 

I don’t think there is a “perfect RPM” answer. It’s more of a personal preference thing.

 

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I don’t think there is a “perfect RPM” answer.

Yeah, I would agree. My preference is to look at the sync at both high and low rpms as well as dynamically (how they track as the throttle is opened) and find the setting that is the best average... this seems to work best of all the methods I've tried. This is somewhat easier to do with a liquid-column manometer but with a little care I think you could do it with a TwinMax as well.

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