Bench sync your carbs

OK, following Rick's Clean your carbs thread to get the carbs set up so they run when reinstalled on the bike a bench sync is required.

To bench sync.

Carbs off the bike.

Looking from the engine side into the carbs you will see the shafts with there butterflys attached.

The sync screws are on the shafts that connect to the shaft on the next carb.

Number 3 carb sync is fixed and is what you match the other 3 carbs to.

I use feeler gauges. With the idle speed screw lowered to close up the butterflys, measure the space at the bottom of the butterfly to the carb body on number 3. It was 0.0015 of an inch on mine.

If you can't get number 3 closed down enough, one of the other butterflys might be closed down too much, open the others up and try again.

It is a good idea to make sure the sync srews are clean, also to turn them each way (2 or 3 turns) a couple of times to make sure they do not bind. This also makes them easyer to adjust when fine tuning with the motor running.

Set the other 3 carbs to 0.0015 inch.

I found that at 0.0015 inch the feeler gauge was flexible enough to use by opening the butterfly, placing the feeler gauge on the bottom of the carbs venturi and gently closing the butterfly. You then loosen or tighten the sync screw until you can just with gentle force pull the gauge out without it grabbing or coming out with no force. I got mine spot on 0.0015. Open and close the butterflys every now and then while you set each one as well to make sure everything is in place.

You have now bench synced the carbs "pretty close".

Make sure float levels are good before putting the carbs back on the bike.

Give the float bowls a light tap, this helps to insure they are not stuck.

Turn the idle speed up a bit (1 turn clockwise), so the bike will idle. Increase a bit more if it won't.

Set the mixture screws to 3 turns from closed.

Start bike (prime and choke). Should start and run ok.
If so go for a ride to warm her up. 15 minutes down the road stop and set idle. Note how bike is running. Go home and (if you have the gear ready, fine tune the sync of the carbs using the guides (have a look at my $5 sync tool or Rick's Old school One Vacuum Gauge FAQ write up). Go for another ride to make sure all is well.

Colour tune or get the mixtures set on a CO meter (some states in the US might have requirements for the bike to meet emission standards).

If you need a YICS tool look at Rick's thread "Free YICS Tool For All".

You can use other things like a piece of wire, paper or tube to measure the sync gap, but a good set of feeler gauges come in handy for other work.

 

Great job. I suggest adding a check to make sure that 2 and 4 are open a bit more than 3, and 1 a bit more than 2 to make sure none of the other butterflies holds 3 open when starting the process, and that 1 doesn't interfere with setting 2.

 

Thanks MiCarl

Noted and added:

If you can't get number 3 closed down enough, one of the other butterflys might be closed down too much, open the others up and try again.

It is a good idea to make sure the sync srews are clean, also to turn them each way (2 or 3 turns) a couple of times to make sure they do not bind. This also makes them easyer to adjust when fine tuning with the motor running.

 

One thing here.

Use a "Feeler" that will CONFORM to the CURVE at the Bottom of the Throttle Plate.

Strips of 3X5 Card ... 1/4-Inch wide make IDEAL "Feelers"

They also allow for the Throttles to be Mechanically Synced NEAR Closed.
THIS is important for when you are Adjusting IDLE Mixtures to run the Bike without bringing-in too much AIR over the Main Jets.

 

Pictures would be awesome, But this will come in handy when I upgrade the jets. thank you.