Carburetor Synchronizer Reading

[christopher_2]

OK first of all is it a joke in the book when it says all the balls should be adjusted to the same line? I am using mercury but can not get mine exactly the same they oscillate around a point and I try to get them to all oscillate about the same point. I can get within a couple of points of each other. Also as you open the throttle and move up the scale how many people here keep a synchronized reading? I am going to check the valves as soon as I get a new gasket. After that is done I am going to check the jetting to make sure it is correct.

[Steve]

If you are not using any kind of restricter in the vacuum lines to dampen out the oscillations, you WILL see a lot of movement. I use mercury sticks, too, and I have to look at the average of where the column is bouncing. The actual reading is not as important as having them all pretty much the same.

Yes, the readings will change as you run up the rpm band. Does not really matter, unless they are drastically different. Blip the throttle a couple of times (carefully, so you don't suck mercury into the engine), check the readings again. You want to make sure that all the carb butterflies are seated properly and maintain sync.

The purpose of synchronization is to get all the carburetors to START at the same point. This gets the smoothest idle and gets them all pulling about the same time when you take off.

Just to make sure you have the tuning sequence right...
1. adjust the valves (they control how much air moves, therefore the amount of vacuum)
2. adjust the timing (if possible)
3. adjust the sync



.

[mark]

The purpose of synchronization is to get all the carburetors to START at the same point.

If that's how you want to synch, that's O.K. Some folks like myself like to synch our carbs at higher rpm's. I synch mine at about 3-4,000 rpm, more toward the kind of revs that the bike will actually be running at most of the time. Usually it ends up being about the same anyway as at idle.

Its a matter of preference, carb synch is not limited to idle speed.

Remember to use a couple of good fans so your engine doesn't overheat.

Steve is right, valves must be adjusted correctly as well.

[bwringer]

I sync at around 2,000 rpm just because that's about the lowest RPM where changes have an immediate effect. If you sync at idle, you often have to blip the throttle to see where they settle.

And don't worry about getting it exactly perfect -- pretty close is pretty good. Those adjustments are VERY touchy, and they tend to go out of whack every time you tighten those stupid locknuts. It takes practice to get just the right feel so it's spot-on when the locknut is tightened. I've done a lot of carb syncs, and I still hate them.

[chef1366]

Don't even bother to sync without adjusting your valves first unless you feel you need the practice. Use a fan like Mark said. It takes patience because without the special tool you need to learn how to compensate for the last bit of torque on the nut. You'll be riding the merry go round. Adjust one and another one changes ect. They pulse and are hard to read. Just keep at it and you'll be a pro before you know it.

[christopher_2]

I had not synchronized the carbs since I bought the bike except on the bench. I was not that far off but am better now. I am not sure the valves even need adjusted, I am going to check them and go from there. I want to make sure everything is good then jet my 29mm Smoothbores.

[ghwrenchit]

OK first of all is it a joke in the book when it says all the balls should be adjusted to the same line?

No, some of the older "factory tools" used steel balls in vacuum gauges.

ghwrenchit