[timdhawk]

So my carbs have been rebuilt and bench tuned by a reputable person. I trust his work. I have my sync gauges set up and they are near identical, but they seem to be pulling lower than normal vacuum. Am I reading them wrong...? if not, what would cause this? everything seems nice and tight in regards to air leaks...

 

[76TWIN]

You didn't say what bike this is for and whether there have been any mods to the carbs and air filtration system.

 

[timdhawk]

****... sorry... 74 cb360. Stock other than K&N filters (which the carbs are set up for) and, I don't know if it makes to much difference but, the exhaust is custom piping (same diameter as stock) and cone mufflers....

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[76TWIN]

If you take the filters off the carbs, does the vacuum go up? If so then it would seems your filters are somehow restricting the air vacuum.

That said what are you expecting the gauge to read? The important part in the carb syncing is that both carbs pull the same amount.

 

[timdhawk]

If you take the filters off the carbs, does the vacuum go up? If so then it would seems your filters are somehow restricting the air vacuum.

That said what are you expecting the gauge to read? The important part in the carb syncing is that both carbs pull the same amount.

Yea, tried filters off, reset the carb bodies into the intake boots (just in case), reset the points gaps, re-double checked static timing and I still run about 1-2 vacuum at 1200rpm idle. Nothing I've tried seems to change how much vacuum... so, at least they are both synced to each other.
I do now seem to have an occasional popping from the right carb as well... lean condition, right? I'm 1 1/2 turns out on the air screw.

 

[76TWIN]

Try another 1/4 turn out and see if the popping goes away.
How do your plugs look?

 

[mike in idaho]

Valve and ignition timing affects vacuum numbers also.

 

[Rob Axel]

I was gonna say check timing (points gap) and valve clearance ...