Carb synch

[Nibsy]

Hi all,
Having an absolute mare trying to synch carbs. No 2 pot is non-adjustable right? So I try to synch 1,3 & 4 to 2. First I synch 1 & 2, but when I then try to synch 3 & 4 it screws up 1 & 2 and they all go out of synch. Surely only one column at a time should be moving. . I’m using Carbtune Pro vacuum gauges.

 

[dannymax]

Each change will affect all carbs. Sync'n requires patients.

 

[Nibsy]

Each change will affect all carbs. Sync'n requires patients.

Yes i’ve been on it for some time….. it’s a fairly warm day here in UK today so the bike is getting hot. The missus is bitching about the noise too so i’ve had to call it for today.

 

[MaxMidnight]

Process is:
Synch #1 carb to #2 (screw on LH side)
Synch #3 to #4 using the rear screw on the RH side
Synch #1 & 2 to #3 & 4 using the front screw on the RH side.

After each adjustment flick the throttle to settle the linkage and adjust further if required.

When done adjust the idle speed and throttle free play.

Go and make 'The Management' a cup of tea.

 

[Nibsy]

Process is:
Synch #1 carb to #2 (screw on LH side)
Synch #3 to #4 using the rear screw on the RH side
Synch #1 & 2 to #3 & 4 using the front screw on the RH side.

After each adjustment flick the throttle to settle the linkage and adjust further if required.

When done adjust the idle speed and throttle free play.

Go and make 'The Management' a cup of tea.

Yep …… been following that procedure, but as soon as I jump on #3 it totally screws up #1 & #2

 

[MaxMidnight]

I wouldn't worry about that if 1 & 2 change they keep the same value relative to each other. Can you synch 3 to 4?
If you can you then synch 1 & 2 to 3 & 4

 

[Dorney]

Left front Carb is your starting point. Read that Carb whatever that Carb is reading that is what you set the rest at. Starting with the Carb right behind it then the right rear then the right front.

 

[Nibsy]

I wouldn't worry about that if 1 & 2 change they keep the same value relative to each other. Can you synch 3 to 4?
If you can you then synch 1 & 2 to 3 & 4

Yep

Left front Carb is your starting point. Read that Carb whatever that Carb is reading that is what you set the rest at. Starting with the Carb right behind it then the right rear then the right front

Yep…. Done all that…… but every carb I adjust alters the settings of the ones I’ve just set previously. I can’t set any one carb and have it stay constant. Even the value of #2 is varying and that’s supposedly the set point.

 

[Fire-medic]

You might want to compare your tool/instrument to another. See if the same thing happens.

 

[Nibsy]

Yep


Yep…. Done all that…… but every carb I adjust alters the settings of the ones I’ve just set previously. I can’t set any one carb and have it stay constant. Even the value of #2 is varying and that’s supposedly the set point.

Yes I was thinking of maybe getting the analog gauge type. I thought the CarbTune was a decent set though

 

[Fire-medic]

It is, but sometimes it's necessary to rule-out such things as you search for the cause(s) of the problem.

 

[dannymax]

Yep


Yep…. Done all that…… but every carb I adjust alters the settings of the ones I’ve just set previously. I can’t set any one carb and have it stay constant. Even the value of #2 is varying and that’s supposedly the set point.

#2 is the master carb that the other 3 carbs get sync'd to...that doesn't mean it stays at a constant setting. Adjustments to the other carbs will affect the vacuum at the #2 carb also.

 

[dannymax]

Did you set up your Carbtune with restrictors in each vacuum hose?

Here is a procedure I wrote up a few years ago, it appears you are already following this but may be something that will help you.

Warm up the motor and adjust the idle to 1100 rpm.
It’s easiest to refer to each carb by it’s factory designated number:

Front

#2 #4

#1 #3

Rear

When you mount the carbs on the bike they sit in the carb boots, the boots fit over aluminum intake manifolds, also called intake runners. Each intake manifold has a brass spigot covered by a rubber cap…except #2 which has a rubber hose going to the vacuum advance.
Disconnect the rubber hose from #2 and remove the rubber caps from the other 3 carburetors. These brass spigots are where you will attach your sync gauge. (I prefer the Carbtune). Attach them in whatever order makes sense to you.
The #2 carb is the master carb, it has no adjusting screw and the other carbs are sync’d to it.
There is one adjusting screw on the left side and two on the right. Look at the left side photo between the lower cover bolts, there is a flat headed slotted screw just below the choke rod…and on the right side note the same type screw head except there is two side by side.
Here is what they do:
-the screw on the left side sync’s the #1 carb to the #2
-the rear screw on the right side sync’s the #3 carb with #4
-the front screw on the right side sync’s the right side carbs ($3 & #4) with the left side carbs (#1 & #2)
Start by syncing #1 to #2
Then syncing #3 to #4
Then sync the right side to the left side.
It takes some practice as every adjustment minutely affects the other carbs.
Make tiny adjustments and blip the throttle after each adjustment allowing time for it to settle out before making the next adjustment.

 

[Dorney]

You might want to compare your tool/instrument to another. See if the same thing happens.

Fire-medic is it possible that his adjusters are rusted some & are affecting the others.

 

[Nibsy]

Did you set up your Carbtune with restrictors in each vacuum hose?

Here is a procedure I wrote up a few years ago, it appears you are already following this but may be something that will help you.

Yes I have the restrictors installed in the CarbTune hoses, all the adjusters are free and turn easily too.

 

[brian hicks]

Yep


Yep…. Done all that…… but every carb I adjust alters the settings of the ones I’ve just set previously. I can’t set any one carb and have it stay constant. Even the value of #2 is varying and that’s supposedly the set point.

Interesting. I recently synced my carbs using 4 meters I bought on ebay and found each carb gave a slightly different reading, so swap the rubber pipes around to check the consistency of the meters before adjusting because some of these meters are rubbish. There are good videos on you tube showing how to sync Vmax carbs.