Vacuum hose question

[substudio]

Just a quick question for the vacuum hoses of the carburetor.

Do any of the vacuum hoses need to be plugged?

I found my bike when I purchased it plugged with a screw.
Is it necessary to plug the:

-Vacuum hose to the left carb
-Vacuum hose from the upper-T connection
http://gstwin.com/images/how_to/fuel%20hose/www_gs500_de_HoseRouting.jpg

[starwalt]

I can recall no plugged hoses for my 90 carbs.

It could be that someone plugged the vac hose that attached to the diaphragm side of the fuel selector switch. When in ON or RES, the diaphragm opens a fuel path to the carbs.

If you are running in PRI constantly, you would not know the difference.

There are some caps for the top parts of the carb for Vac balancing but that was not your question.

[Boone13]

 Hello. My question is similar to the first question. I have a 1990 GS and I was looking at the racing mods page on the website. The author of the mods page suggested a Power-Flo fuel valve to replace both the tank and the frame mounted fuel valves. This mod would simplify all the hose routing and connection problems. My question concerns the vacuum line. I should probably plug that inlet on the left carburetor if I make this modification. Am I correct in surmising that the purpose of the vacuum line is to keep the fuel valve open, on the stock set-up?

  I'd like to make a general comment about this site. I LOVE it. I bought my GS brand new as a leftover '90 model in 1991. Over the years, I've been deployed many times for the military and the GS has been largely unridden for the past 15 years.
I had many inquiries for selling the bike, however, I am glad that I kept it. Over the past few weeks, with the help of this site, I've cleaned up the carburetor and my current project is taking care of the rust on the tank, both inside and out. I wouldn't have had the urge to start these projects if not for wandering upon this website. 
                                                                                                                          Boone 

[starwalt]

I believe you are correct that when you go to the other fuel selectors, just cap the vac line.

GSTwin is a great resource. I have lots of pics of my 90 rework/repairs on my AT&T/Bellsouth website. Look in my profile for the link.

BTW, thanks for your (and all our other military members) service. 

[Boone13]

Thanks Doug.
                     I'm just doing my job. I've been deployed for the National Guard more than I've been deployed while I was active duty. In hindsight, I would've put twenty in on the Active side. I could be retired right now!

I'll just be happy when I get the GS running again and I can enjoy my summer and not depend so much on the House of Saud for my petroleum needs.
                 
                                                       Boone.

[ben2go]

The top T between the carbs is for venting so the fuel bowls don't become pressurized by the heat from the engine.The only vacuum line plugged on my carbs is the one to the petcock.My petcock has been modified to not use vacuum.If you are running on PRIme all the time you will experience fuel starvation.The orifice inside the petcock is half the size of the hose fittings.Here's to solutions.

This eliminates the vacuum operation.I do this mod for $10 and that includes return shipping.Takes me over night to do it and ship it back.
http://gstwins.com/gsboard/index.php?topic=19363.0

This is a cheap solution that uses no vaccum.
http://gstwins.com/gsboard/index.php?topic=36958.0

WARNING!
You need a way of stopping the flow of fuel when the engine is not running.If a float in the carb should stick,the crank case and air box will become flooded with gas.This could cause an engine to blow up while riding.If an engine locks up while riding the rear wheel will lock up.