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Thu Jan 03, 2013 7:51 pm

I have an motorcyle carb sync tool. Its a long stick with mercury tubes. I'll be installing weber ict. Can I just connect my sync gauge to the balance ports on manifolds. Will this work to sync?

Lastly, is perfect sync really all that important when using balance tube?

Thu Jan 03, 2013 8:30 pm

will not work with those carbs, needs isolated barrels

Fri Jan 04, 2013 5:11 am

Those are the same set up as my Kadrons that I run. I built a homemeade manometer which essentialy is a 14' hose with with a big long U and partially filled with 2 stroke oil.

I connect the hose to the balance tube port on each carb and match them. Works amazingly well.

I have not used the actual motorcycle tool, but there is no reason to believe that it wont work as well. As far as perfect synch - if you can get it, why not? I mean, why would you want one side of the engine doing more work than the other.

Fri Jan 04, 2013 5:14 am

that is what I thought. I didn't see any reason why it wouldn't work. Vacuum is a vacuum, unless I am missing

Fri Jan 04, 2013 6:48 am

My Dell 45's have a port tapped next to the air bypass screws, on all four barrels. From what I have read it is to use the type of synchronizer you are talking about. It doesn't appear to be straight manifold vacuum though.

Fri Jan 04, 2013 6:53 am

I haven’t ordered my Weber ICT’s yet, but I think only one carb has a vacuum port on it? I believe they get the vacuum signal from just under the throttle plate so it should be the same signal? I know on my bikes there was a nipple right on rubber manifold.

Any one know if the ICTs have vacuum ports on both carbs? Should be easier hooking there if so.

Fri Jan 04, 2013 1:42 pm

Sure - one way or another you can make it work. I used to use my motorcycle setup to snc and tune my Alpha's twin sidedraft two barrels. It was the fancy kind with four vacuum gauges mounted on a bar that you hung on the hood for easy reading.

It's best if there's a port (under the throttle plates?) but any way you can devise to close up the venturi that lets air through and has a hook in for a vacuum tube will work. Probably whatever your bike kit has for taking readings from the smaller intakes of the bikes can be figured out to work the same way.

Like you say; vacuum is vacuum.

Fri Jan 04, 2013 1:49 pm

Last question: how important is sync when a balance tube is used? I have read that when a tube is in place sync is not really all that important assuming the carbs are in the ball park. Is this a myth? Trying to weight my options and figure out if I want to dump another $50 on a snail sync tool and adaptor. If I can bench sync and install balance tube that saves me 50.

Fri Jan 04, 2013 1:54 pm

Myth. Balance tube smoothes idle on dual single barrels. They still need to be synchronized.

Fri Jan 04, 2013 1:59 pm

Sync is important. It should be checked not only at idle, but at various throttle openings to see if one carb is leading the other after the linkage is hooked back up. ICTs will usually have one port for vacuum on each carb ... neither of which can be used with a Carb Stixx type manometer. The carb vacuum ports are ported above the throttle plates (for the vacuum advance distributor connection). You should use the balance ports on the manifolds (as you mentioned) to measure with your motorcycle sync tool.

Fri Jan 04, 2013 4:31 pm

It's a kind of two part process.

One thing is to make sure that all the throttle plates open the same amount at the same time. Usually a two barrel carburator's two throttle plates will be in sync unless there's something wrong with the carb itself - the plates mounted incorrectly or damaged, the plate 'axle' bent or it's bushings shot. So you only need work with the two carbs whether single or double bore unless something's damaged or wore out.

( bad throttle plate rod bushings can play hell with the second part because they can allow air in that makes accurate mixture settings near impossible. Be sure that your parts are in good shape.)

The second part is probably more important and more difficult. The gauges help be sure that the airflow through the carburators is matched. That airflow can be affected by the mixture, the valve conditions, the cylinder/ring sealing as well as float levels and jetting. You're wanting to know how much each cylinder is sucking and make adjustments or repairs to get all of them in a zone you think of as good enough.

Try not to let it drive you off your branch. A lot of people think that only a perfect match is good enough. Those folks go bald early, have ulcers, and usually die younger than they would if they could have relaxed a little.

Most of us in the forum suffer that perfectionist malady, often refered to as 'being anal'. :)

The "snail" type tool is good - better than the old Unisyn both because it measures all the flow instead of segmenting a reduced sample and because it gives a nice solid read that's a lot easier to use than trying to guestimate the levels of a bubble in a tube that fluctuates as you watch it. Wish they'd thought of snail types when I was a kid. You can find it cheaper than the $50. figure but it's worth it's price at the fifty, IMO.