very little vacuum on number 6 Help please

[z13phil]

Hi Guy's, just been syncing the carbs, As the book says using number 4 as the base carb. 1-2-3--5 all adjustable and seem to be working as they should.
Problem with number 6 what ever way you adjust the screw no difference, and showing very little vacuum. Not responsive.
Pressure checked the cylinder, all OK.
No leaks from the rubber inlet, tested with WD40 while running.
But when connecting a tube to the vacuum outlets, then sucking or blowing! no resistance. Where as all the others you can feel a resistance on all the other carbs !
Thanks in advance

[NobleHops]

Phil, this could only be the result of a blockage in the port or the intake tract. Probe the open port, after shining a strong light into it. If there is a blockage, you need to remove the carbs to investigate or risk whatever it is being suciked into the cylinder.

[bobcat]

Tight intake valve ? Check valve clearances ? Try pulling the choke all the way closed then see if
there's any change in resistance in the vacuum hose.

[z13phil]

Thanks for that

[bobcat]

What puzzles me is that you said the (compression?) pressure checks out good.
You might also try turning the motor over by hand while sucking/lowing the vacuum tube to see
if the resistance (or lack of) changes. One last thing, look at the throttle linkage connection
between 5 and six carbs for mis assembly. If the washers that go on either side of the off the
lifting fork are out of place* it could be holding the no. six butterfly open making adjustment
nearly impossible.
*compare to the other linkages.

[daves79x]

Are you sure #6 is firing? Never tried to sync without all six firing, so don't know what you'd see.

Dave