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View Results: What tool do you use to measure vacuum/vacuum differences for throttle body syncs?
Harmonizer 13 25.00%
Morgan Carb Tune 7 13.46%
Twinmax 15 28.85%
Homemade Manometer (please explain) 13 25.00%
Other (please specify) 4 7.69%
Voters: 52. You may not vote on this poll

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Old 10-24-2012, 05:39 PM   #1
SpeedySteve OP
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Tool for measuring vacuum/vacuum difference for TB/carb sync

Howdy Folks -

I picked up a new 2012 BMW GSAdventure bike over the summer. I am acquiring the tools/manuals/knowledge to maintain this bike (hopefully) myself, unless something epic hits the fan. The last tool on the immediate scope is a vacuum gauge, or a vacuum difference gauge to assist me in syncing the throttle bodies on this bike. Fairly standard procedure for most twins, and there are heaps of options out there to help measure or identify vacuum differences.

Anyways, I am basically curious what tool y'all are using to measure vacuum or vacuum differences on twin cylinder bikes. I am shopping for a tool that is accurate, reliable and easy to use.

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ADVmember GROK used to make this 'harmonizer' device - the device preferred for this procedure on the beemer. However, he has taken a different plath in life and no longer making these for the time being. This is the desired tool, but I can't get one.

Morgan Carb Tune
So, I don't have many use cases on this tool nor have I done much reading on it yet. This was recommended as an alternative to the Twinmax from a few sources. Seems to be another 'tried and true' tool dating back to late 80s.

Meh, it's been around forever, and this 'sensitivity' knob. I am a bit leary of this device, I don't feel it has the accuracy/sensitivity to perform syncs within the +/- 10mbar range (acceptable tolerance of the GS I have is +/- 25mbar apparently. Reading the BMW service manual tonight).

Home made Manometers
Well, clear tubing, a yard stick, tape and ATF are always an option I guess.

I am quite interested in how different folks accomplish this task. Please vote and feel free to chime in!

Please specify the bike you used this tool on and your success.

Thanks in advance! Cheers, Steve
2012 BMW GSA - yeehaw! 5 years of drooling, finally did it.
2003 SV650s

SpeedySteve screwed with this post 10-24-2012 at 05:50 PM
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Old 10-24-2012, 05:48 PM   #2
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I bought a Twinmax, but I didn't need it's portability (I NEVER used it whilst on the road) I sold the Twinmax after I built my own manometer.

I prefer using the Manaometer because it was easier to use, didn't need zeroing and I believe it to be more accurate (no matter how much I tried to set the sensitivity control the Twinmax needle would always jitter about some).

I don't use the Manomater often enough (every service), I didn't use the Twinmax often enough either.

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Old 10-24-2012, 06:52 PM   #3
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Motion Pro, duh!

SV's and DL's. Works great.
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Old 10-24-2012, 07:13 PM   #4
Stalky Tracker
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I have and use the Morgan. I use it on the Wee (Suzuki DL650). Easy to use and works great. Never had a problem with it.
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Old 10-24-2012, 09:40 PM   #5
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Carb Stix-

Old school mercury manometer works well for most bikes. Simple and effective- it is all I need

I have used it on my 1100RT, Ducati, Honda, etc.. with great results.
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Old 10-24-2012, 10:36 PM   #6
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I've been using Carb Stix for years on my BMW''s. Purchased a Harmonizer a year ago and really like it.
A simlpe homemade manometer will do the same thing though.

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Old 10-25-2012, 02:21 PM   #7
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Harmonizer is much more useful to me than Carb Stix (mercury) or home made manometer. The early 1100 has a single cross-over type throttle cable. Can't really find an ideal sync. Have to settle for a compromise and that means testing under load on the road. You never loose your investment on quality test instruments. Gauge function helpful. Buying from one of our own is a bonus.
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Old 10-26-2012, 06:14 AM   #8
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Originally Posted by stalky tracker View Post
i have and use the morgan. I use it on the wee (suzuki dl650). Easy to use and works great. Never had a problem with it.
+ 1 And it werks on multi cylinder bikes in case you ever sell yer soul.
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Old 10-26-2012, 06:56 AM   #9
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I used a Motion Pro mercury carb stick for years and years. I got a TwinMax for portability. I do a lot of bike work for friends.

The mercury sticks were great. The TwinMax, I hate. On the TwinMax, it would drift off calibration at times in the middle of setting the balance. You work and work. the engine starts getting too hot. You get it perfect. Shut it down. And realize the TwinMax drifted, so you are now off balance. Maybe worse then when you started, as I had happen a couple of times. I say maybe, because the reading of that bouncing needle has no reference, so is it off badly, or just a little? And I never got it straight in my head which way the needle goes with the most vacuum (my fault I guess). And the needle needs more damping, as it bounces a lot with the big twin Guzzi. And at the maximum sensitivity, it is barely good enough.

But, my mercury carb sticks went bad. the mercury oxidized over the years and would fill the tube with air bubbles. I had to dispose of those. So now all I have is the suck TwinMax. I suspect I will at some point do the home made tube with some ATF in it

Luckily, must of the bikes I work on now are fuel injected. The mechanical linkages are enough better that they hold sync very well for a few years.
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Old 10-27-2012, 06:58 AM   #10
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Done I-4, V-4, V-2 an of course the boxer. Worked best after I filled a brass coupling with JB weld and drilled a 3/32" hole in it. Slowed the fluctuations down.

You can also build one for 4 bangers. I just used the above one to match cyl 2,3 and 4 to cyl 1.

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Old 10-31-2012, 10:43 AM   #11
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I have a Harmonizer --I used it primarily on my R1100S (boxer-twin) but now on my FZ1 (i-4). Works great!

Easy to use, nicely built. I really like the portability of it compared to mercury sticks and the like (fits in with my mobile lifestyle and easy to loan). Less fussy in operation than the Twinmax.
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