Carb Hose Question - Why would hoses be capped?

[shenquay]

Why would someone cap the carb vent hose and the vacuum hose that runs from the carbs to the back of the frame petcock?

Bought a 97 GS500 last summer that conked out on me in the fall. Over winter I rebuilt the carbs and now trying to get it started again. I'm having a lot of trouble getting the bike to idle and not continually climb in RPM's when starting. It always climbs to 7k RPM's with no sign of stopping before I shut it off. While rebuilding the carbs I realized the owner before me was an idiot. One reason is because he had the carb vent hose and the vacuum hose capped. I took off the caps and have the vacuum hose going to the back of the frame petcock and the carb vent hose draping over the air box like in diagrams I've found. But with the problems I've been having with the bike continually climbing in RPM's, I'm wondering if there was a reason he capped the hoses.

I'm pretty confident that I rebuilt the carbs right so I think the issue is somewhere else. If I cap the carb air vent hose the bike will not start at all. If I un-cap the hose the bike immediately starts but climbs in RPM's. From my research, this hose is just a fuel overflow hose and shouldn't affect airflow to the carbs. I'm just trying to get more info on my situation and get my bike running again.

[mr72]

If the choke is on then rpm rising to 7k is sort of normal. Lower the idle speed so it only revs to about 5k then dial in the idle speed and mixture only after it's fully warmed up.

Only way it revs too high at idle is if the idle throttle stop is set too open. Takes air to rev. A vacuum leak could cause it to not idle slow enough and high floats can exacerbate this problem but start with idle speed adjustment.

[Kilted1]

I can't speak to why someone would cap those hoses.  But if you have things the way they're supposed to be then it's just a matter of adjustment.  For a cold start you're naturally going to turn the choke on full.  As it warms up the revs are going to climb so just ease the choke back instead of killing it.  You'll probably have to do this several times before the choke is fully off and the bike idles normally.  Also we often end up with the idle set high because it's adjusted by impatient people who don't understand that it takes a good bit of riding before it's fully warmed up, so the idle gets set while it's cold and thus ends up being high.