Bench Sync

[Krunk_Kracker]

I'm not seeing an info on how to do it on here or on BassCliffs site, anyone have any info?

[Krunk_Kracker]

Apologies, I wasn't looking in the right area of BassCliff's site.

I found it:

Bench Sync Your CV Carbs
By Mr. Steve (Woodin)

To bench sync the carbs, you do need to have the rack assembled, but not on the bike. Open the master idle speed adjuster until carb #3 has a gap in the throttle plate that is large enough to put something in. That 'something' needs to be small, like a paper clip. Adjust the idle speed adjuster so there is just a light drag on the paper clip, much like you do when checking the valves. You will see adjuster mechanisms between the carbs, so loosen the locknut, adjust the screw so you have the same amount of drag on carb #2, then carb #1. After doing those two (in that order), do carb #4. Now adjust the master idle screw out to close the throttles back down. I like to close them completely, then back in about a turn or two. When you start the bike, be ready to hit the kill switch if the idle speed is still set too high and the engine races when it starts. Back the idle speed screw out some more and start the engine again. When you have the engine warmed up and are ready to do the vacuum sync, use the same order of adjustment.

Notes from other members:
From Mr. KiwiGS
Assemble carbs [in the rack like they are] ready to go on the bike.
Set air screws 1 1/2 turns from bottom [from lightly seated].
Determine master carb [#3]. The one that the throttle cable connects to right?
Put a small drill bit 1.5mm under the butterfly of the master carb.
Adjust the main idle screw until the butterfly just touches the drill bit.
Adjust the sync screws until all of the butterflys are the same.
Check the master carb again.
Reset the idle screw.
Additional comments from:
Mr. chef1366: I use a flexible feeler gauge [instead of a drill bit]. #3 is the master carb.
Mr. Steve: Start at 2 full turns out and use a smaller gauge. I have had a couple sets of carbs that would not open to 1.5 mm, so I use a straightened-out paper clip. The larger ones I have available at home are 1.05 mm in diameter, the 'normal' size clips are 0.88 mm. Just be sure that there are no burrs on the end of the clip that will scratch the throat of the carb. Also, don't forget to re-set the idle speed before starting the bike. With the throttle open far enough to do the bench sync, revs will tend to skyrocket when started.
Ms. SqDancerLynn1: The only thing I would add is to make sure the #3 throttle blade is completely closed with the idle screw backed out. You never know what was done in the past.
Mr. Steve (again): Ms. Lynn makes a good point. What I tend to do when finished is to back off the idle screw until there is a gap in the adjuster, then shine a light through all the carb throats to verify that they all are closed. Then do a visual sync as I turn the idle adjuster until it touches, then about one turn more.

[1_v8_merc]

Yep it's really easy and straight forward.

If you got a really good eye, and spend a long time benching it to the "T", you might not even need to do a REAL sync with gauges.
(myself included)

You should still get a sync gauge though, it's that ONE tool everyone seems to ask their buddies for!

[earlfor]

The purpose of a bench synch is to get it to run well enough that you can do a proper carb sync. You may think your ear got it right, but you will only believe that until you put vacuum gauges on it and see how far out you actually are. I've not found anyone that can do what I would call an acceptable carb synch by ear, self included.

Earl

[dueller]

You should still get a sync gauge though, it's that ONE tool everyone seems to ask their buddies for!

Or get a buddy that will accept beer and brats for a sync job BTW, anyone between Lansing and Novi, Mi have one that wants to make it pay for itself Just got my carbs on.....Startup tomorrow.

[Krunk_Kracker]

I have a buddy who works at a motorcycle shop whos going to do it for $40 using mercury sticks, although I have no idea what that means.

[chuck hahn]

That means he is gonna hook 4 tubes up tom your carbs that have mercury in them. The vaccuum from each cylinder will draw the mercury up each of the corresponding tubes. Then he is gonna adjust the screws at the backs of each carb so that the levels of mercury in all 4 tubes is as close to the same level a possible.

[esj001]

http://www.thegsresources.com/_forum/showthread.php?t=175634

Or check out this thread and make your own for bout 10 bucks that works really well (IMO of course)
---check out my video toward the end of the thread if you want to see what it looks like.

[mike-s]

I have been told that one reason that mercury sticks are popular (though i don't know how easy they are to obtain now) is that the weight of the mercury resisting the vacuum provides pretty good dampening and provides an average of how much draw is oneach cylinder rather than spiking all over the place like vacuum guages can sometimes do if they don't have dampening built in to them to help smooth the display out.

[dueller]

Aren't the hooked up

That means he is gonna hook 4 tubes up tom your carbs that have mercury in them. The vaccuum from each cylinder will draw the mercury up each of the corresponding tubes. Then he is gonna adjust the screws at the backs of each carb so that the levels of mercury in all 4 tubes is as close to the same level a possible.

to the head? At least that's where they are on my 700 Just didn't want someone who doesn't know to try it themselves and wonder where they are supposed to hook them up to their carbs.

[chuck hahn]

to the intake boot between the carbs and the head theres a allen head bolt right at the botom and at an angle so you can hook the adapters to the boots. You take out that allen head and the adapter screws in there.

[Krunk_Kracker]

Can someone clarify this for me:

Open the master idle speed adjuster until carb #3 has a gap in the throttle plate that is large enough to put something in. That 'something' needs to be small, like a paper clip. Adjust the idle speed adjuster so there is just a light drag on the paper clip, much like you do when checking the valves. You will see adjuster mechanisms between the carbs, so loosen the locknut, adjust the screw so you have the same amount of drag on carb #2, then carb #1.

Where exactly am I putting the paper clip to test the drag? I'm having a hard time visualizing it.

:EDIT:

This is talking about the butterfly valves isn't it?

[mike-s]

Yes it is.

[esj001]

Yes ---you want the butterfly valves to be open the same amount or as close as you can get it---if you use the paperclip method just make sure you put it in the throats of the carbs in the same place on each carb (usually the 6 oclock position)--Use the paperclip like a feeler guage, you just want slight drag on the clip as you pull it from between the butterfly valve and the throat of the carb. Careful dont scratch up the throat or valves. I did this and then I used the "sliver of light method" hold the carbs up to the light and turn the idle screw (which will move all four at once) open until you get a sliver of light shining through--you can see if one has a bigger sliver than the others, adjust as needed---when i did this on my carb rebuild, the motorcycle started right up and ran good---but you need to do a proper sync when you can to make it better.

[Dakotakid]

Guys, thank you very much for your diligence in responding to this thread. I am at this stage, tonight, for the sleeping '82 GS 850 GZ. This procedure was pretty much what common sense told me....but, this allowed a bit more clarity.

This GS is in such great shape (13,000 miles), always garaged, but sat for long periods of time. I really want this babe running soon in order to dampen my libido for the GPZ....yuk! I'm going through too much gas money in the red rocket and (according to Einstein), I get younger every time I ride it....due to the speed. Soon...I'll be back in trainer pants! Oops....my nose is getting a bit longer now....gotta go!