carb syncing and timing advancement

[cowboy]

i was wondering about carb sync tools i see a few different ones on feebay and was wondering if i could use a 2 carb sync tool since my 78 has the key hole type carbs on it that are all tuned off the number 2 carb instead of buying the 4 carb tool is it better to go with a manometer type tool for syncing

i have figured out that my bike wouldn't idle do to the timing being off and the ignition coil or points feeding 2 and 3 cyl was not firing right so i order new parts to fix them but was wondering about advancing or retarding the timing for any kind of extra hp or torque or anything any secrets or advice

[Piute]

  not sure you understand that the other 3 carbs need to be the same as #2 my 77 f2 has key type but still havn't synced them but have it very close for know ,there all come apart again in a few more months .
 when I redo / check everthing over winter.

[cowboy]

yeah i understand that sorry if it came across wrong thats why i wondered about using a two gauge set up and leaving one on the number 2 carb and moving the other one to the other three carbs to sync them all to number two

but just thought about something i have read about ppl bench syncing there carbs first how is that done and or why

my carbs don't look any where near that pretty lol i really just want to get this bike up and running and ride it before it gets to cold out at which point i think i will start trying to make it look a lot better but just don't no or understand how to paint chrome and or things like the carbs so they don't look messed up

[Peterwh]

The idea seems to have some logical merit, you would just have to keep swapping the gauges over.  Is the two carb device significantly cheaper than the four carb one?

[cowboy]

its about half price really but i only have this one bike that has 4 carbs on it everything else in the garage a is a 2 smoke stroker so single carb setup's and don't really want to drop a bunch of money on a tool that i will only use once or maybe twice

thats why i was wondering if buying the 2 gauge setup is doable or if 4 is better or easier or basicly the same with less work

what is the difference between the tubed manometer things and actual gauge setups good bad or whatever

[Peterwh]

I have a four gauge set myself that I got from Vintage CB 750 for around $100.  I'm not sure about a manometer as I've never used one but there are instructions on the web for howmto build your own for about $15 or less.

I guess, in theory, you could use just a single gauge ie check the vacuum on the reference carb then do the others one at a time.

Where are you?  If you are anywhere near Pittsburgh, you can use mine.

[TOOLS1]

Here, you go. $65.00. You will be glad, you got them. I have this same set, and they work great. You could do it with a two gauge set up, but it would be a real pain. You would need to keep moving the fittings around on a hot engine which is no fun. As, for bench bleeding. That would be a real pain also. You would have to remove the carbs to do it, and then it is not very accurate.
TOOLS

[shinyribs]

I got the same $65 set that Tools has.In fact,he showed me where to get mine.Worth every penny
http://www.ebay.com/itm/Vacuum-Carburetor-Synchronizer-carb-sync-Gauge-CB-GS-KZ-550-650-750-850-/330625117736?pt=Motors_Automotive_Tools&vxp=mtr&hash=item4cfacaee28

The kit in this link is actually nicer than mine.It has the two super long brass extensions that i wish mine had.Cheaper,too!

[Peterwh]

The one from Vintage CB750 comes in a nice wood case - worth every cent of the extra $40!!!

[Lucky 1]

With those gauges you would still need to mount them on a board. Those long brass tubes would get broken off right at the threaded portion very easily because the brass is VERY thin. then you have a broken off brass part in the carb!  They get broken ALL THE TIME!
Also all four of the gauges are not the same spring tension and would not get as good a result as a manometer type gauge.

That is why you do not see them used as much as the manometer type gauge.
Remember before syncing the carbs first you have to get all four gauges to read the same all hooked to #2 carb.
With those round spring operated gauges there is NO adjustment to get them to all be the same.
See photo below.
When you sync carbs it is the LAST thing you do in a tune up.
But before you can sync the carbs you need to get all four of the gauge levels to be the same while they are connected to #2 carb. This is explained in the instructions that come with the Motion Pro gauge manometer.

Then you hook the vacuum tubes to the other carbs to get all of the carbs syncronized.

Also on that 1978 set of carbs (so called Keyhole style) they have an accelerator pump feature.
If that is NOT operating the carbs will not work right at all.
Look into the opening of the carb and you will see a small brass tube sticking up in each carb. When the throttle is advanced those little tubes spray gas into the engine. The gas sprays out the side of the tube NOT out the top of the tube.
If you just turn the throttle with the engine off and the gas turned on you should see ALL 4 of them squirt a stream of gas into the carbs.

If it does not work forget about syncing the carbs until you get that corrected and working properly.
The accelerator pump has two check valves with a steel spring loaded ball and the one in the bottom part is critical. If that part does not work right you can try to clean it but  if it does not fix the problem then you will have to replace it. It costs $85.00  Fortunately I was able to get one.
Good thing too or I would have had to get one some other way or get a new set of carbs. There is no work around that I could think of.

The other check ball is in the top of the float bowl edge. IT does not usually get messed up as the bottom check valve because it can drain down but the bottom check valve ball is where dirt and water can collect and cause corrosion damage.








EDIT: July 2013.
After using the dial type vacuum gauges I would NEVER
 go back to the fluid type gauges - too much trouble!

[LukeM]

Good input, Donald.  Thanks.  Agreed that if using dial gauges, hook up all 2 or 4 gauges to a single vacuum source, and verify they have the same reading.

It's possible to use a 2 gauge set to sync a 4 carb setup.  Synchronize 3 and 4, then sync 1 and 2, and then sync the 3-4 pair with the 1-2 pair. It can be done, but having 4 gauges for 4 carbs works much quicker.

Luke M

[TOOLS1]

I am going to have to defend my gauges. They are mounted on a plate that can be safety wired, or bungee corded to the handle bars. They are adjustable. However when I checked them to the same vacuum source they were all right on the money. The brass tubes are pretty stout. It would take some abuse to break them.
Also the manometer style is supposed to be more accurate, but, for a stock street engine the gauges are more then adequate. Also who wants to mess around with Mercury? The stuff is poison! I do not want it around my home/garage. I would not want my Grandchildren, or Toolmutts to get anywhere near it.
TOOLS

[sgtslag]

Here is the link to the home-built manometer:

http://www.powerchutes.com/manometer.asp

Have not built one, or used one, but thought I'd share the link.  The price is definitely right.  Cheers!

[cowboy]

wow thanks for all the input on the carb sync tools

my next question would be about timing factory timing best or slight advance or retard better

and thanks for the input on the pump bearing donald big thank you thought i cleaned everything on the three cleaning lol but i didn't realize that existed in there i will have to check that out and make sure it got cleaned or is atleast in working order

[shinyribs]

I have to take Tools back on this one,too.Our gauges (Tools and myself)might not be the "best"out there,but they get the job done.They came pre-mounted on a very nice plate,and mine all read dead nuts identical to one another as well.I am sure there are fancier kits,but these work just fine.If you break off one of these brass tubes while slipping on a vacuum hose...well,you are probably too ham-fisted to be working on carburetors in the first place.JMO


Though nothing removes lead build up from a guns rifling as well as mercury does.Just a thought...
     -This statement has not been approved by the EPA,FDA,NRA or anyone else with good sense-

[pedro bighead]

Thanks for the information on the ball and spring, however nowhere on this blog are the actual instructions for syncing the F2 carb set. I have the 4 gauge sync set and found my 1 and 4 are 5 psi light. Where are the instructions that say you need to take this apart and and turn this nut and screw which is on this part inside the carb? (replace "this part and that part" with the procedure and the name of the part or parts that are being turned or screwed in or out) There is no air jet on these carbs, only a fuel mixture jet which will not change the air pressure inside the carb throat, it only leans out or richens your mixture. If you crack the throttle and gas spurts out into the carb throat the pump is working. the 77 has no third brass tube sticking into the throat it has 2 tubes and 2 holes. Noone here that i have read seems to know how to sync these carbs. Other wise the instructions would be here in a step by step format and so far i cant find the actual procedure for syncing the keyhole carbs. Just a lot of advice on which gauges are needed. any help would be appreciated

[TOOLS1]

On the F-2, F-3, 77-78 K, and the 76-78 A models you remove the tops of the No#1, #3, and #4 carbs (No#2 is the control, and not adjustable, so no need to remove it's top). There is a little screw with a set nut in the top of the carbs. You loosen the set screw, and adjust to match the No#2 carb. Be sure to blip the throttle after each adjustment. If the idle starts to chang, adjust it with the main idle set screw on the right front of the rack.
TOOLS