Topic: Bench Synching Carbs

[MattFreeman]

I've looked so I apologize if this has been covered else ware. I am attempting to get my F1 going after a total teardown.

When using the "drill bit" method for bench synching do you gap at the filter side of the carb or the engine side?

If I adjust so there is a tiny gap at the filter side of the slide the engine side seems fully closed. It would seem to my uneducated mind that this would keep the engine from getting any fuel.

And I guess while I've got your attention I'll mention that carb #3 isn't getting any gas at all, the bowl is dry. The new float valve seems to be fine so I figure there must be a clog between the t fitting in the line and the float valve. Thoughts?

Pod/jetting questions to come, you've been warned 

[OldSchool_IsCool]

I think the filter side of the slide si beveled where as the engine side is flat.  Adjust from the flat side, i.e. engine side.

[MattFreeman]

I've done that and it doesn't really seem right...

[Tdinova]

do it on the engine side. the other side(filter) is the choke. Bench will some times be close or way off. It all depends on the vacuum from each cyl

[Deltarider]

I did the engine side and used a small allen key, not a drill bit. When I checked afterwards with vac gauges, it turned out they were within 2cm Hg of eachother and that's well within factory specs. I haven't used my set ever since.

[PeWe]

Bench routine the Mikuni way. I did from the wrong side, filter side were the throttles have the opening. Result OK despite drill bit under the open side of throttles. Engine side might be easier to get it right with carbs on bench. I did also a visual synch back in yhe days. Lookinh yhru the carbs so a small ray o light was visible. Held the carb rack against strong light as sunshine...

[flybox1]

drill bit goes in on intake side during a bench sync
yes, you want the slide to be fully seated when the idle set screw is turned out. if it doesnt you wont be able to get the bike to idle low enough.
I only know the latter F and K carbs, but you might have a slave carb #2 on your F1 carbs.  you'll want to bench sync all the others to match this one.

turn in your idle set screw until your drill bit fits under the intake side slide cutout.  tur out your idle set screw so the slide lowers onto the bit, lightly pinching it.  do not touch your idle set screw from here on out.
loosen the slide lock nut under the top cap of #1 carb, and raise the slide.  insert bit, lower slide so it creates the same resistance felt on #2.  tighten the lock nut on #1.  #1 is now the same as #2....repeat the above for 3 & 4
done

[lucky]

I've looked so I apologize if this has been covered else ware. I am attempting to get my F1 going after a total teardown.

When using the "drill bit" method for bench synching do you gap at the filter side of the carb or the engine side?

If I adjust so there is a tiny gap at the filter side of the slide the engine side seems fully closed. It would seem to my uneducated mind that this would keep the engine from getting any fuel.

And I guess while I've got your attention I'll mention that carb #3 isn't getting any gas at all, the bowl is dry. The new float valve seems to be fine so I figure there must be a clog between the t fitting in the line and the float valve. Thoughts?

Pod/jetting questions to come, you've been warned 

Do not use this "drill bit" method on this bike and these carbs.
Make sure all of the slides are fully closed with the throttle off.
 Then with the air cleaners off engine, off check by using your finger to see that when you start to open the throttle that all of the slides begins to move at the same time.


Adjusting the slides up or down even .007 thousandths of an inch will make a difference in the idle.
When you sync carbs you are adjusting the amount of air of each carb at idle.

Do not adjust  mixture screws when syncing carbs. All mixture screws should be set at  same number of turns out.

[Cevan]

I just did my F1 recently.  I used a 1/8" drill bit on the intake side and it was close enough to get it running.  I sync'd it with a gauge type manometer.  The adjustment screws on top are very sensitive. 

[lrutt]

I've bench synched many 4cyl bikes with 100% success. Honestly don't remember which side though but I know slide cut aways usually dictate which will work. For splayed cable carbies (think Guzzi, BMW, Trumpet) it's the only way to go if you don't have vac ports.

[martin99]

I always do them from the intake side, it's how I set up the twin monoblocs on the Norton. With the carbs on the bike, and a drill bit under each slide, you can twist the throttle and adjust until movement of the drill bits (dropping down as the slides are raised) is identical by eyeballing them from the side. I imagine with four carbs you could do it this way with four drill bits, never tried it though