Equalizer line instead of syncing carbs

I basically brought my Mikuni BS34s back from the dead. They had sat for years with old fuel, and water in them, and I spent a lot of time getting all the varnish, rust, and corrosion out. It has been a long road with these carbs. I never ordered a rebuild kit for them, and literally filed the fins down a few RCHs( use your imagination) off the float needles so they would not drag in the seat bores, which had corrosion. Ergo, I have had to devote a lot of thought and time to achieving carb unison.
I may eventually fully implement this idea, but not now. I do not want to butcher my intake tubes. But, what is great about this forum is that there may be a tinkerer out there with a shop, and some parts laying around who might see the value in this "equalizer" idea. I personally think it would be almost like having one carb. Mano-syncing is important, but from what I understand, KZ carbs with enrichment shafts DO NOT warm up smoothly, and this might help.:S

I agree with that an equalizer might be a good idea AFTER syncing. In response to the other post, I do not think that vacuum nipples would be of sufficient size to make a difference.

Won't work.

OK You don't believe me, that is fine I have only been working on these since 1978 and some of that at a Kawasaki dealership. You can do what ever you think will work. Between all the cars and motorcycles that have and do use individual carbs since the 1920s you would think that someone somewhere has figured it out. I guess I will have to go to the school I went to and ask for a refund because they taught me wrong.

Last post. IM-OTTO-HERE. :silly:

Otto, actually I do believe you. I guess I am just prone to arguing,and I regret having defended this idea so doggedly.:S
I guess our own ideas are like out little babies. We think they are the greatest. Outta here, David

David, Yamaha used a process similar to what you are thinking of. A chamber roughly 5/8ths in diameter ran thru the cyl head & accessed all 4 intake bores. It was called Yamaha intake control system (YICS) (not you idiot c@#%- sucker as many supposed) carb sync'ing was still required, & was possible via a special block-off tool. If intested, research the @ '81 Seca 750 & some others.GB)

Gane, ty for posting. After researching the YICS, I think the idea is feasible. My carbs will probably never be perfect until I sync them to find the miscreants, replace them, or at a minimum, buy some kits for them.
Sometimes after my bike sits, it will lose one or two cyls at idle. Maybe some of the needles are leaking, and flooding the float bowl. I have never used a manometer. It seems to me that a manometer may not indicate a fuel problem- is the vacuum the same whether the cyl is firing or not? :X

Well, I for one am confused. I thought the whole idea of syncing the carbs with a manometer was so they DO have equal vacuum at idle! I still think this true, as the actual adjustment only effects the butterflys. It's necessary because of minor differences in how each carb is set up (miniscule differences in slider heights, response to jets, linkage tolerances, air flow in particular, etc.). If true, a common equalizing tube as suggested, would cause some carbs to steal from each other, and you'd end up with mixture feed differences (if only slight) in different cylinders. I can't see any advantage to the proposed idea.

At idle, if the carbs are out of sync, but you put a balance tube to connect all four intakes together through ports in the manifolds, you have a mismatch based on firing order and distances between cylinders. The air in the tube has momentum so depending on which way the air happens to flow will affect how much each cylinder gets. This will run as uneven as having the carbs out of sync and no tube.

If you run a tube from each manifold to a central chamber so each intake has equal access to the chamber, it still won't work since the differenctial from one cylinder's carb, relative to the average vacuum in the chamber, will be different for each cylinder. Each cylinder then gets a different amount of charge.

Obviously both options will work if the carbs are all in sync, but then you don't need the contraption at all.

The only way it would work is if the 4 carbs feed into a large box, then the large box is connected to the cylinders. But you'd never do this because then you could just use one big carb to feed the box... much simpler.

If there was a way to eliminate the need to sync the carbs for $2 worth of vacuum hose and some cheap Tee's, wouldn't Kawasaki have done it? That would have saved hours of factory setup.

polkat wrote:

Well, I for one am confused. I thought the whole idea of syncing the carbs with a manometer was so they DO have equal vacuum at idle! I still think this true, as the actual adjustment only effects the butterflys. It's necessary because of minor differences in how each carb is set up (miniscule differences in slider heights, response to jets, linkage tolerances, air flow in particular, etc.). If true, a common equalizing tube as suggested, would cause some carbs to steal from each other, and you'd end up with mixture feed differences (if only slight) in different cylinders. I can't see any advantage to the proposed idea.

Correct about it not working.

You don't really care about the actual vacuum to the cylinders. The point is to get each cylinder to do equal work in turning the crank to get a smooth idle.

You only use the vacuum as an indicator. This is based on the assumption that each cylinder is in the same state of wear... a faulty assumption unless you check with a compression test. In fact, if the cylinders are worn differently, you want the vacuum to actually be different. A cylinder with lower compression should show lower vacuum, but by how much is hard to predict.

Another way to sync is to setup the carbs to a 4-1 manifold and hook it up to an external vacuum source. Then at least you know each carb is open the same amount... something a manometer on the engine does not guarantee. But that still does not mean each cylinder gets the same charge. A weaker cylinder will get less charge in this method.

The truest test is to use an oscilloscope and look at the alternator pulse widths relative to the firing of each cylinder. This will tell you crank speed for each firing of a cylinder. You adjust the carbs so each firing results in the same crank acceleration.

You will need a battery to run the bike and disconnect the stator so you can measure it with no load so the puls's width is not altered by load. Then you have to sync the scope to each coil seperately to compare stator pulse widths. Because each coil fires two cylinders, you will have to do trial and error to figure which cyclinder is which in the pair.

That's a whole lot of work, but not impossible.

By the way, no, I do not try to do all that, I just slap on a manometer.