Advice syncing carbs on a 79 750F

[AcMedic]

I’m pretty sure I know the answer, but need to be confirmed. I have a 79 750F. Just bought a sync gauge setup. Online tutorials that I’ve viewed say to hook the gauge for #2 carb to the vacuum port that operates the peacock. My 79 has a philips head screw on the inlet of #2 just like all the other carbs. So, my thought is that I use #2 as the base and bring 1, 3, and 4 into sync with #2. Do I have this right? I’ve done a search on the forum for the answer but couldn’t find one. Thanks in advance!

 

[brettp]

That's correct for a 79-82 cb750k. Probably the same for yours.

 

[AcMedic]

That's correct for a 79-82 cb750k. Probably the same for yours.

Thanks. Only a few minor differences between the K and F.

 

[brettp]

I think it's a 7 or 8mm lock nut on the screw that adjusts the vacuum for carbs 1, 3, 4. I bought a set of thin wrenches (they look like toys, lol) but they came in really handy. Pro tip: when you have the vacuum set correctly, back the screw out about 1/8 of a turn (half of a quarter turn), snug the lock nut to the screw and then tighten up the lock nut with that 1/8 turn. Mine vacuum screw had a tendency to screw in a bit when tightening the lock nut. A lot of force is not necessary, nor required, to tighten it but the screw did turn with it.

 

[Nayoalex]

in all intakes you have cross screws. maybe in one you have a tube that goes to the petcock.

In that little tube you have to put a derivation in "t" so that it goes to the synchronizer but that it continues keeping the tube in the petcock.

If you do not do so, the motorcycle will shut down due to lack of gasoline.

There are several ways to do it.

The simplest is:
with the screw between #1 and #2 you synchronize those two carburettors.
With the screw between #3 and #4 you do the same.
and then with the central one you equalize the two.

Keep in mind that if at 1100 rpm you leave them perfect, but at 3000/3500 rpm they are not the same, you will find the bike better if you match them at 3500 rpm. And if they differ a lot, you share "the difference".

This is because even if idle rpm is not perfect, you will be fine at normal use rpm.

Keep in mind that it greatly influences how well the motorcycle is set up in many aspects. Perfect spark plugs, perfect spark plug wires, perfect valve clearance...etc. It seeks to match in the regime that you most often use the motorcycle.

 

[Robert Frere]

I’m pretty sure I know the answer, but need to be confirmed. I have a 79 750F. Just bought a sync gauge setup. Online tutorials that I’ve viewed say to hook the gauge for #2 carb to the vacuum port that operates the peacock. My 79 has a philips head screw on the inlet of #2 just like all the other carbs. So, my thought is that I use #2 as the base and bring 1, 3, and 4 into sync with #2. Do I have this right? I’ve done a search on the forum for the answer but couldn’t find one. Thanks in advance!

That's the way I do my 1978F2 number 2 carb on mine is non adjustable so u sinc all the others to it

 

[Robert Frere]

I think it's a 7 or 8mm lock nut on the screw that adjusts the vacuum for carbs 1, 3, 4. I bought a set of thin wrenches (they look like toys, lol) but they came in really handy. Pro tip: when you have the vacuum set correctly, back the screw out about 1/8 of a turn (half of a quarter turn), snug the lock nut to the screw and then tighten up the lock nut with that 1/8 turn. Mine vacuum screw had a tendency to screw in a bit when tightening the lock nut. A lot of force is not necessary, nor required, to tighten it but the screw did turn with it.

Hi I have a really good tool for adjusting the vacuum nuts its alongish hollow tube with an eight mm socket welded on the end and inside is a thin flat screwdriver and the top of the tube has a shortish flat bar to use to undo and tighten up the nuts