Carb Sync Procedure - 3rd Gen

I'm planning to sync my carbs for the first time this weekend and I want to know if there's any special tricks to get it right. My plan is as follows:

1. Attach the 4 vacuum gage cluster
2. Start bike and allow to come up to temperature
3. adjust idle mixture screws to 2 and 1/2 turns
4. synchronize the carbs as best I can
5. readjust the idle screws (fine tuning)
6. readjust the synchronization if necessary (fine tuning)
7. Celebrate my great success

Will that procedure work? Are there any tricks to getting to the hookup points for the gages; mine seem to be rather hard to get to upon first glance? I haven't checked my valve adjustments either - is that something I should do before I mess with the carbs or will that not affect this?

Thanks for the feedback!

 

IC has it right, and be sure to snap the throttle a few times between adjustments to settle the linkages and butterflys into their new position.

Each synch screw adjustment seems to slightly affect the other carbs, you're working upside-down in a mostly blind area in a hot environment, and it's not fun. Kneel down with a flashlight so you can see the screws while you're turning.

Another suggestion is not to use a screwdriver point, but rather a small socket to turn the hexhead adjustment screws.

Be sure to note the initial gague readings before you start adjusting, cuz it's not too difficult to work half an hour and find all your adjustments have gotten things worse !!

 

You did not tell us which BRAND of sync tool is being used.

FIRST- adjust the pilot air screws to the desired amount. Don't move them anymore.
SECOND- Get the idle down to around 1200 rpm.
NEXT- The vacuum guages MUST be calibrated.
What that REALLY means is getting #3 cylinder (the non adjustable carb),
To show at a decent level on the sych tool.
I am NOT going to explain it step by step here.
But you have to read your instructions.
Guages must BE CALIBRATED FIRST! Using cylinder #3. (the one that has no adjustment of the rod that turns the butterfly)
THEN you can hook #1 guage port to # 1 cylinder and the other cylinders on the motorcycle.

Then you can adjust (synch) the butterfly valves on the carbs.
1 and 3 THEN 4 and 2. (4 and 2 has only one adjustment)

You really need to get some help.

If you don't have the instructions for the guage you better let us know.
Otherwise there is no way to get it done correctly.

Engineers!! chhheeessshhh!!!

 

Sorry, Tinki, you deserve the credit.

And Don, those are fuel screws, not air screws. Important cuz going clockwise on AIR screws richens mixture, while clockwise on FUEL screws leans it out.

 

I was a dealer ship mechanic on the first vacuum operated carburated fours, when
WE had to make our own vacuum guages to get the job done.
I started working in a motorcycle shop when I was 16 and we got the first Honda 50's.
I worked all the way up until the first 750 fours were introduced.
The first ones did NOT have vacuum operated carbs. That was later on.

 

All of the new vacuum operated carbs have fuel enrichment screws. NOT air pilot screws. Those adjustments adjust fuel /air mixture during the first 1/4 throttle.

Its funny how all the young men think they know everything.
I was troubleshooting fuel injection systems while you were still in diapers.

 

Yes the "base" carb for each of the models may be different.

VF1000F/R Cylinder #3 base carb. VF1100's also have a different firing order.
Other models may be different. It is up to the mechanic to find that out.
I can't be there to hold your hand people.

You must read the manual and learn details on your own.
I can only point out general principles.

Also when the manual says regurator we know it should be regulator now don't we? But really a rectifier.

 

"You can calibrate the gauges using any vacuum port you can easily reach." This is not correct. When they say"calibrate" it does NOT mean the guages per se. What that actually means, is that the BASE carb does NOT have a adjustment screw to open the butterfly and when you hook the guages up to THAT cylinder you adjust the GUAGE fluid adjustment knobs to get the fluid level to be about 1/3 up on the scale. Then you are really matching the other 3 cylinders to THAT level of the BASE carb after that. The "calibration" of that base cylinder has to be done with the plastic manifold that is supplied with the vacuum guage. All four hoses from the guage are hooked to the plastic manifold and a short hose 5th port on the manifold goes to the base cylinder during the "calibration " of the base cylinder. And the vacuum restrictors must be in the hose ends (if required) Any way read your instructions and if you threw them out you better get a copy.

 

"Another suggestion is not to use a screwdriver point, but rather a small socket to turn the hexhead adjustment screws." Very good sugggestion!!! Otherwise it is impossible.

 

Young man?? Don, i'm older than you !!

My synch screws (gen 2) have screw-slotted hex heads , so either tool will work.

 

Right, I agree.
If the base carb throttle shaft bushing are worn it will be impossible to balance.

 

Okay, I've done a first run-through on it and I think it's greatly improved. It sounds much better at any rate. The right rear vacuum port is super hard to get to; whoever decided to put a bunch of stuff in the way should be shot or at least made to feel quite silly. I took a couple of pictures and will post them later. Time for a test ride!

 

The Honda VF v4 engines have one of the worst designs for working on carbs that I have seen HONDA manufacture.