Carb synch settings for 1978 GS1000EC

[P248]

I need to synchronise the VM26 carbs on my 1978 GS1000EC. According to the factory workshop manual the carbs on the two middle cylinders should be set to a different vacuum setting c/w the setting for the outer cylinders.

Does anyone know what the difference should be between the vacuum readings for the middle cylinders c/w the outer ones? The bike is completely standard, including OE exhaust silencers.

The factory service manual gives details with reference to the special Suzuki factory synchro tool which uses balls set to a base comparison setting. It does not give a value for the difference in terms of mm Hg (mercury) which can be measured using more conventional synchro tools such as vacuum gauges or Morgan Carbtune. The Haynes manual suggests they should all be at the same setting, which is definitely not correct.

 

[steve murdoch]

Welcome to the site.
Have a look through this tutorial from bwinger.
http://www.bwringer.com/gs/carbsync.html

 

[Agemax]

Always set them even across the board, never caused an issue and idles like a swiss watch.

 

[Steve]

Most of us have always set the levels straight across. In fact, I never knew about Suzuki's suggestion for the different levels until I joined this fourm a dozen years ago.

I have just about every type of sync gauge except the dials, so I experimented a bit just for the fun of it. I set my carbs straight across with my mercury gauges, then connected my Suzuki ball gauges. I then adjusted the gauge until it also read with the balls straight across. I then adjusted the carbs so the two outer ones were half a ball higher, as suggested. I then re-connected my mercury gauges to see what the difference was. The difference was right at 2 cm.

I have seen several theories why to set them differently, but none of them made sense, so I continue to set them straight across.

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