Vacuum Tuning

[AustinPhoenix]

Question for you technical guys...or guru's...or anybody that might know the answer.

If I buy a single vacuum gauge, hook it up to each carb individually (of course I would be re-attaching the Vacuum seals after each carb and reattach the emissions hose to the petcock directly instead of through the T), would this effectively vacuum sync the carbs? I know it will take much longer than just hooking up 4 and tuning them while watching the gauges....but I'm cheap and don't want to spend the $100 RIGHT NOW! I will eventually...just not now.

[petejw]

yep, you can,
you can also get a 4 into 1 adaptor
from an aquarium shop, makes the job a little easier.

[Ken Talbot]

This will get your carbs closer, but it will not get them sync'd. As you adjust one carb, you are always working with a slightly fluctuating reading. As you move to another carb, you would be trying to set to a reading that is based on things that were happening in another carb, not necessarily the one you're now working on. The beauty of mercury sticks is you get the columns for the two carbs you're working on right next to each other, within a half inch. It is very easy to see the intercacion between two carbs as you work. A pair of round vacuum gauges is better than one, but you still have the issue of watching two fluctuating needles which are not visually close to each other.

If ca$h is tight, I think you would probably get as close with a single round gauge as you would with the variation of the bread tie method where you visually adjust the butterflies to where each just about covers one of the orifices in the carb throat. I.e., keep that money towards eventually getting the proper tool.

[oldyam80sg]

The bread tie method does work if anyone has doubts.I cleaned my carbs and followed the bread tie method and the bike runs smoother than before.Now i can drive to my Moms house where i can do a proper sync.

[petejw]

i shouldve added its not very accurate. :-)

[AustinPhoenix]

eh...oh well

It was worth a shot! lol

[oseaghdha]

Originally posted by oldyam80sg
The bread tie method does work if anyone has doubts.I cleaned my carbs and followed the bread tie method and the bike runs smoother than before.Now i can drive to my Moms house where i can do a proper sync.

Yer mom has a set of stix?

[oldyam80sg]

No- thats where all my tools and future work will be done.I was just informed at my storage unit that i really should not be doing any kind of repairs there.So i told the owner that the bike needs to run to get it to my moms house where i can work on it further.He said that someone complained that the bike is too loud.

[AustinPhoenix]

in college...

...I knew a guy that rented two storage units next to each other in a climate controlled storage center. He had his car and bike parked in one, and he lived in the other. He showered and did all his bathroom stuff at the gym when he'd work out in the morning. He paid around $270 a month total.

The guy complaining probably lived there. You should complain about him.

[oldyam80sg]

Actually it was a woman.I told the owner that i live in the next town and have a storage unit facility less than 2 miles away and i will go there if thats what they want.He sees me everyday working on the bike and has not said a word since.But i think in July i will relocate for my convenience.

[John]

I have a set of JC Whipme gauges that I paid $65 for and they suck! After the first use, the needles wouldn't go back to zero, even after using the face plate adjusting screws. I just used some T fittings, and short lenghts of hose to make a manifold, and used the dampeners from the gauge set. It does take a little longer to do the job, because changes made to one carb will affect the other, but by going back to the previous carb after making changes to it's neighbor, you can dial them in just right, and still end up with all four the same. It just takes a little longer. When I finished I had all carbs at 14 inches of mercury, and I could lower the idle to 700 and it still idled smoothly. I don't have a decent tach, but you can tell by ear what sounds like a good idle speed. Mine is set to 1100 rpm as shown on the bikes' tach.

[skids]

Fourteen inches!! That is really a lot of vacuum pressure. I would say that you have some good fitting manifold boots.

Originally posted by John
(snip) When I finished I had all carbs at 14 inches of mercury, and I could lower the idle to 700 and it still idled smoothly. I(snip)

[Dragon Tamer]

Single gauge syncing WILL work, yes it is slower and a little more irritating but it will work. The main issue here is that when you read the first carb you must note the engine RPM, all subsequent carbs must be set to THAT vacuum level at THAT RPM. The problem being that every time you adjust a carb the RPM will change and you must constantly reset it back to where it was when you started!
I have recently been using a digital manometer to sync and it will do a beautifull job but at around $700 for one with a comparator system it means that you have to have other uses for it also. The only reason that I have a couple around is that part of what I do for a living involves balancing air flow in ductwork, it struck me one day that that should not be a whole lot different than balancing air flow in my carbs. For once I was correct.

[AustinPhoenix]

Ahhh

That helps out tremendously! Thanks Tamer! For now, a single gauge will have to work. But in the future, a proper tool will be purchased for sure.

Just so I have the structure down, I will do the following:

Petcock to PRI
Fan on
Warm up engine to proper temp
Sync carbs 3 to 4 with the screw that's between them
Sync carbs 1 to 2 with the screw between them
Sync both pairs with the screw between 2 and 3.

A guy that rebuilds older bikes (cb750s, kawi, etc etc) told me that he syncs his bikes to 4 or 5k rpm because that's where he's always at. Is that the same for us? Good idea? Is there a difference between the rpms as long as they're all the same when you're synching?

[ross]

been there...done that....

hey there AustinPhoenix...i hate to go against the forum, but single gauge vacuum gauge syncing will get you close, but not quite....trust me, i have been 6 months trying 2 get the carbs right and once you have the 4 gauge setup, you will see the difference.....one adjustment to one carb will change the setting of the other carb....best is to have 4 gauges to set them....best way i found was to go to the local tool place (harbor freight).....buy 4 vacuum gauges...do your test, settings and such....then simply return them and get your $$$ back.....colortuning is recommended, but if you can tune them in by ear, that is good enough......colortune gets you close, but you still have 2 b able to tune them in by ear to get it right.....you will know when this happens as your bike will wanna jump right outta the garage......trust me, when you get it right, it will be like night and day.....pucker factor will be a "10"....good luck and good riding...ross