What is up with vacuum?

[Anonymous]

I have noticed my bike runs great without the the vacuum tube(on carb three) plugged, in other words,open to vac the outside air. When plugged the exhaust pops and the number two carb backfires. I installed a K&N airfilter and have been told that could cause the carb backfire(I'm currently checking into that), I have found no leaks in the exhaust, however I could be looking in the wrong places.
Why would the bike run better without the vac line plugged and how does one check the exhaust for leaks?

[Anonymous]

Not sure what you are talking about here. I have a 1000 and the input between #2 and #3 is the fuel line input with the 5/8" nipple. My vacuum line is above that coming off #3 carb. Could you have those hoses switched? One vacuum line goes back to the petcock to pull the diaphragm open to allow fuel into the carbs only when the engine is running. the other two vacuum lines should have long rubber hoses on them and can just drop down behind the engine since they are not used.

[frosty5011]

If the hoses are hooked up correctly, and bike runs without vacuum tube hooked up, then your vacuum-operated petcock (assuming that is what you still have on the bike) is shot.

(Unless you're running it in the PRIME position)

[Anonymous]

The vac line runs from the #3 carb while the other hoses are routed up and around the back of the airbox. The diaphram of the petcock is non-functional(a rebuild kit is on the way) so when I bought the bike it was not hooked up, just hanging. Another member said I should plug the vac hose so I did and all heck broke loose!(see above!). When I UNplugged the hose all returned to normal and it rides just fine. I just completed about 5 laps around the neighborhood without any pops, backfires, and without the bike running way too hot, something else it was doing with the hose plugged. When hooked up to the petcock is the hose completely "plugged" or does it take in "some" air? It certainly does NOT like being completely stopped up! 8O

[moto_dan]

The vac line runs from the #3 carb while the other hoses are routed up and around the back of the airbox. The diaphram of the petcock is non-functional(a rebuild kit is on the way) so when I bought the bike it was not hooked up, just hanging. Another member said I should plug the vac hose so I did and all heck broke loose!(see above!). When I UNplugged the hose all returned to normal and it rides just fine. I just completed about 5 laps around the neighborhood without any pops, backfires, and without the bike running way too hot, something else it was doing with the hose plugged. When hooked up to the petcock is the hose completely "plugged" or does it take in "some" air? It certainly does NOT like being completely stopped up! 8O

Not sure, but if you were told to disconnect and plug the vacuum line, then you were probably also told to switch the petrooster to Prime. If not then this would explain the erractic running and overheating condition...
Bike would be starving for fuel...extreme lean condition.