Hello,

I was trying to fix a problem that is probably related to a vacuum leak.
When I removed the tank I discovered that one of the connectors of the left carburetor was broken off.
However, I do not know what the part is that it is supposed to be attached to.

So, what is the part circled in red?
And is it a problem that the connector circled in blue is broken?

The part circled in red is called a vacuum chamber.
See: https://www.bikebandit.com/2004-suzuki-gs500f/o/m6061#sch503304

It might be possible to drill out the broken off pipe to the same diameter and epoxying in a short piece of brass tube... or even the broken off piece of plastic tube, depending on where it broke off. It is quite long. I recommend using J-B Weld as it can withstand 500 °F (260 °C).

Thank you for this insight!

I don't think welding is necessary, since it is a plastic part that is broken off, see the attached image.

Could the broken part explain a high, erratic idle when the motorcycle has warmed up?
That's the problem I'm trying to fix, the idle hangs at around 3000 rpm when the motorcycle is warmed up.

It's not clear from your picture if the hose is attached properly and leak free. I'd make sure that it is before trying other troubleshooting options. Having said that, I'm not adept at tuning the GS500 engine and I have never had a hanging idle problem with my bike, so can't advise you on it.

But I can show you a trick I use to better search the GSTwins forum. I use Google with very specific keywords separated by "OR". Try entering this in Google: hanging or idle or site:gstwins.com

Or click here: https://www.google.com/search?q=hanging+or+idle+or+site:gstwins.com

You should be able to find your answer in one of the links. Good luck.


PS The aspect ratio of your last picture is wrong because the width and height values are swapped.  (width="922" height="435" should be: width="435" height="922")

An airleak into the carbs definitely can give  a hanging idle.

SK, you bring washed away with all the rain?

Quote from: herennow on November 08, 2020, 12:39:07 AM
SK, you bring washed away with all the rain?

Nope.. ?

Quote from: SK Racing on November 07, 2020, 09:57:15 AM
The part circled in red is called a vacuum chamber.
See: https://www.bikebandit.com/2004-suzuki-gs500f/o/m6061#sch503304

It might be possible to drill out the broken off pipe to the same diameter and epoxying in a short piece of brass tube... or even the broken off piece of plastic tube, depending on where it broke off. It is quite long. I recommend using J-B Weld as it can withstand 500 °F (260 °C).

I've been known to make repair such as that!

A small piece of tubing that sits into both pieces will work as a mender .

This is the best epoxy I've found for that sort of repair. It's pale yellow in color, smells strongly of acrylic solvent when mixed, and is strong.  The only time I use the clear is when I want a less noticeable repair.

Thanks for all the information!

What I don't understand is, why is the left nozzle of the right carb not connected to anything? Won't that also cause a vacuum leak? Should it be connected to the vacuum chamber?

You're correct. There should be no unconnected pipes or nozzles. Fortunately, the carbs are off my bike and I took a few photos to show where all the vacuum pipes are connected. Keep in mind it is a 2004/5 GS500F without PAIR.


This view from the front of the carbs shows all the vacuum pipes that should be connected to your carbs.


Coming round to the right hand side, you'll notice two pipes going down to the solenoid at the bottom of the right hand carb. Note the check valve on the one pipe.


And in the rear view, the two pipes connecting to the solenoid.


PS You'll notice that the solenoid has a third connection, a small brass pipe. Yours may have a small plastic part covering the brass pipe. Mine hasn't. It's not important whether it has it or not. It will run fine either way.

Thanks for the pictures and descriptions SK Racing!

Today I changed the vacuum hose connections to how they should be according to the service manual, which is almost the same as how you have connected it.

The hoses were routed really strangely originally (see vacuum_hose_before.png), now they are routed as shown in vacuum_hose_after.png.

It still runs fine, I'm not sure that it runs better yet, only time will tell.
However, I have a fear that a previous owner decided to bypass the solenoid for a reason, maybe it doesn't operate correctly, I will have to see if I experience any problems.