Manometer idea for carb sync's

loudhvx wrote:

The problem with that is that the manometer would have to be super tall.

A 2-foot mercury manometer would have to be replaced by a 20-foot water manometer. Oil would have to be even taller.

Some folks in this thread were saying that they had never been able to have the suction move it higher than 30" even with a vacuum. Is that because it was fighting with the other carb so they were balancing each other out or something?

It would seem at some point, gravity would overcome the power of the vacuum that the carb is generating which would make the 20' long line not required.

Am I missing something?

There are two types of manometers discussed here. The store-bought mercury manometers show each cylinder's vacuum relative to atmospheric pressure. To re-create that with water or oil, would require a 20 to 30 foot manometer.

In order to get an oil or water manometer to be reasonable in size, you have to seal the system and make it into a differential manometer. That's where you are not measuring the vacuum, but simply comparing one vacuum to another. Either type, theoretically, should work, but in practice I think the differential type requires more work, patience, and vigilance (to avoid sucking the fluid into the motor).

Tubes set into an open bucket of oil or water represents the store-bought mercury type. In that case, the manometer will need to be 20 to 30 feet. (Even if the reading will be in the 10 foot range, you need a safety margin for when you blip the throttle.) I think mercury is around 13 times heavier than water, so 1 foot of mercury requires 13 feet of water.

Here's a website w/pix that will explain the 1-2, 3-4,2-3 thing:
771doug.netfirms.com/synch_page.html

This picture shows you where that adjustment will be made. The "A" screw will synch carb #3 to #4, the "B" screw will synch carb #1 to #2, and the "C' screw will synch the 2 pairs to each other


This guy pushed carb jets into the ends of his tubing to reduce fluid jump and get a better reading:
www.zivney.net/library/carbsync.pdf

Post edited by: Spot, at: 2008/01/21 09:04

loudhvx wrote:

Tubes set into an open bucket of oil or water represents the store-bought mercury type. In that case, the manometer will need to be 20 to 30 feet.

Now I follow what's happening, thanks for explaining it.

I just used this idea to sync the carbs on my 650. I thought it worked great... except that if the balance is too far out, you'll suck fluid into the engine. And engines don't like that. I have a recommendation for an improvement; I recommend that you put a restriction of some type at the bottom of the loop of tubing (in the middle) to dampen the response. I used a pair of vice grips. I'd also like to hear any ideas for preventing fluid from getting sucked into the engine. I want to do this to my ZZR1200, but I'm not willing to risk sucking anything into that engine. I feel like that would be a very expensive experience.

bemoore wrote:

I just used this idea to sync the carbs on my 650. I thought it worked great... except that if the balance is too far out, you'll suck fluid into the engine. And engines don't like that. I have a recommendation for an improvement; I recommend that you put a restriction of some type at the bottom of the loop of tubing (in the middle) to dampen the response. I used a pair of vice grips. I'd also like to hear any ideas for preventing fluid from getting sucked into the engine. I want to do this to my ZZR1200, but I'm not willing to risk sucking anything into that engine. I feel like that would be a very expensive experience.

I used a clamp on the bottom when I did my carbs. I used ATF fluid. I warmed up my engine before hooking up the tubes to the vacuum ports, so it would idle immediately after startup. Keep the clamp closed until the engine settles down to the adjusting speed, and slowly open the clamp. If one side starts to rush up the tube into the engine, kill it or clamp the tube tighter. Be ready to adjust the carb as soon as you can. Because oil is lighter than mercury, I figured if I could get the two levels within an inch of each other it would be pretty darn good.
I setup carb 1-2, adjust synch, adjust the idle, shut it off. Setup carb 1-3, adjust synch on 3, adjust idle, shut it off. Setup 1-4, adjust synch on 4, adjust idle, shut down.

I don't know, but my bike is almost vibration free, gets great mileage, smooth power delivery. I must have done something right.

Well, since the member, that originally suggested this, hasn't chimed in, I will.
I forget who originally posted this but I got a pair of these:
tinyurl.com/ytpo79
The seller will put a restrictor into them,(to dampen fluctuation) for I think $0.50
Hook up hoses and balance away. Worked well, for my twin.

Just pony up the $60 and do it right. Using oil or colored water will just suchk the stuff into the cylindrs. If you try colored water, get ready to use a 20' step ladder. watre has less than 1/10 the density of mercury.
Don't let people scare you in to thinking you going to fall dead from using the stuff either. Pure hogwash.
My 82 year old Dad used it to polish dimes when he was a kid.

I think the differential one is a good idea. you just gotta clamp it somewhere along the way so that you can hook it up and not suck stuff in. That way you can have water in it if you like, and nothing gets sucked in unless your carbs are waaaay out.

How about this: synch 2&3, now that they're the same, synch 1 to 2 and 4 to 3. Now all are operating at the same manifold pressure theoretically, three steps. Dont forget to run at 2-3000rpm to smooth out any transient response.

The problem with doing 1&2 then 3&4 is that each pair will be at a different pressure.

Ok, question. How about the 29mm smoothbore carbs. I only noticed two outlets on the carbs themselves. Would you hook up to the manifold gaskets or how exactly does that work?

Ok, almost forgot this one. It is that if you use pods the two outside carbs starve for air while the two inside carbs run rich which is what I heard years ago and it makes sense to me that the four will never breathe the same when riding at speed. What gives? Is this why it is so hard to get the settings just right with pods and what could be done to make that better?
Still a babe in the woulds. Soon I will. I have to in order to make riding a bike almost as old as myself worthwhile. I rode a zrx 1200 today and still feel my bike felt like more of a muscle bike. You have to rev the crap out of those bikes to get feeling the torque and by then you are going to fast to really enjoy it. I like feeling the low end grunt and feeling like you are going fast when in reality it may not be all that fast. I think though that these bikes hold their own against any new bike for style, class and fun to rideness. I still look at a fixed up kz and see so much more of a bike than any new bike could ever offer up. All the new junk is like a flash in the pan with a few bikes being the exception but mostly the way they look they have designed the coolness out of them and another to be leaning over busting your family jewels and abusing your future children not to mention getting carpel tunnel from leaning on the wrist too much what the heck kind of fun is that. Race bikes are great on the track as are race cars but are no fun in the real world. Sorry to digress so much but it's late and my experience today with the zrex 1200 I thought I would enjoy so much more than my kz and in reality it didn't happen. Long live the kz well beyond its years I say!