Mikuni Carbs

[CatatonicBug]

All four of my intake manifolds have vacuum ports on them, of course three of them are capped.

Are you talking about the rubber pieces, or the carbs themselves? All 4 of the rubber pieces should have vacuum ports on them, and those are used for sync'ing the carbs. The Advance line does NOT connect to any of those 4 ports. It connects to the actual carb body. Do all 4 of your actual carb bodies have ports too??

[whiskey pete]

Since I got the bike the vacuum advance has always been attached to the #1 rubber intake manifold. The #2 carb does have what appears to be a vacuum port available but it has always been capped off. Any thoughts????

[CatatonicBug]

Since I got the bike the vacuum advance has always been attached to the #1 rubber intake manifold. The #2 carb does have what appears to be a vacuum port available but it has always been capped off. Any thoughts????

Yeah.. It's backwards! Put the vacuum advance line on the #2 carb port, and the cap on the rubber manifold. The only thing that should be connected to the rubber manifold ports is the vacuum-operated petcocks (on the Standards) or the octy (on the Specials). If you have manual petcocks, all 4 ports should be capped off.

[whiskey pete]

When I put the carbs back on I will attach the advance to the #2 carb. Just like my wife...Works no matter what hole you use.

[crazy steve]

http://www.xs11.com/forum/showthread...=ported+vacuum

Again, go to this thread and look to see if that port on #2 is the same as shown in the pics in post 21. If it is, that's where you want to hook your vacuum advance (without the 'inline' damper).

The main thing to note here is the port is only open to manifold vacuum when the throttle is open. If it's open at all times, that may explain why yours is set-up the way it is; the PO may have got the 'best' results that way. But you may still have issues with the vacuum advance coming in at idle/too fast/too slow/not enough, depending on how your damper is adjusted.

[whiskey pete]

The exploded view of the carb shows the Cap over the port as a vacuum cap. Why the PO used the manifold who knows..If I hook up to the #2 Carb and it does not work out changing back to the manifold is a easy fix. Thanks for the help.