carb adjustment 1/4 turn diffference ???

[motospotter]

I always wondered why the carbs were a 1/4 turn different when you started the adjustment process ? I'm just curious not doing carbs today.

from the handbook-

"To adjust, tighten the screw and then undo it 2 to 2 1/2 turns for the left cylinder carburetor and 2 1/4 to 2 3/4 turns for the right cylinder carburetor."

[ampm7]

My guess is that the right cylinder is like a team of horses. There is only one leader and the others just bring up the rear. In other words, it needs a little more gas.

[TOMB]

There is a difference in the manifold pressure .

Put some  guages the manifolds you'll see the diffrence.

TOMB

[chuck peterson]

Boom
Boom
Pause
Pause

2 cylinder 90 degree single crankpin does that

The first boom needs a little more gas

The right cylinder has to do a touch more work

As opposed to

Boom
Pause
Boom
Pause

It only took 5 years of explaining by TOMB for me to understand that

[motospotter]

Now I know, it was something I always had done but wasn't sure why exactly. THANKS !

[Wayne Orwig]

My wild a$$ guess......


Obviously, if you are truly changing the amount of fuel, then you would need to match it with a change in the air, the keep the mixture right. Just letting in more fuel without the air, doesn't do much.
And since we typically balance the vacuum, the amount of air should be close to the same.
What I suspect goes on is that the engine RPM has changed. At idle speed, the motor has slowed a bit before that first BOOM. And at the lower speed, the carb isn't going to supply as much fuel even though it is pulling all the air it needs. So you need to richen it a bit. The first BOOM increased the RPM, so the second BOOM has less troubling drawing fuel. It is unnoticed at higher RPM. 

[mtiberio]

they use the same carb body casting to do both right and left carbs. They then drill the idle stop threads and idle mixture threads on the correct side for each. Slight differences in the casting due to internal idle circuit channels or simply the fuel line banjo mount mean there is more "meat" on the side that needs more turns out.

[motospotter]

they use the same carb body casting to do both right and left carbs. They then drill the idle stop threads and idle mixture threads on the correct side for each. Slight differences in the casting due to internal idle circuit channels or simply the fuel line banjo mount mean there is more "meat" on the side that needs more turns out.

I only recently noticed the carbs were designated left and right VHB30CS and VHB30CD I just installed them with the adjustment screws easily accessible... It took me only 14 Moto Guzzi bikes to learn these details. 

[moto]

they use the same carb body casting to do both right and left carbs. They then drill the idle stop threads and idle mixture threads on the correct side for each. Slight differences in the casting due to internal idle circuit channels or simply the fuel line banjo mount mean there is more "meat" on the side that needs more turns out.

Do you know this to be true? If not, it should be easy to check with the carbs removed. It's a plausible explanation.