Motorcycle Repair: fuel vacum, petcock, manual

Question
Hi. I have a 1991 Suzuki GSX600F and on the fuel tap (petcock) there two fuel outlets and one vacum. Can you tell me where, or what dose the fuel tap vacum connect to please. Regards Tony.

Answer
This information should be in your shop manual. If you don't have a shop manual you should get one - your bike is old and you will have a hard time finding a shop that will work on it. The sad fact is that a lot of the mechanics working now are too young to remember bikes this old and aren't interested in learning about them so that they can do a proper job since yours may be the only one they see this year. This means that you will have to do most of your own work, and working on a bike without a good shop manual is just not worth the headaches. (My bikes are even older - that's why I fix them myself.)

I recommend that you get two manuals - a Factory Shop Manual and a Haynes or Clymer. That way when you don't understand the explanation in one you will probably figure it out when you have read the other too. If you spend some time on Google you might even find a factory manual available for free download.

That said (& not having access to a manual for your model), I don't think your petcock actually has two fuel outlets. Older vacuum operated petcocks generally have an outlet and a vacuum port. The outlet is connected to the fuel inlet of the carb assembly by a 1/4" or 5/16" fuel line and the vacuum is connected to a barb on one of the carbs by a smaller hose. Later petcocks came with a third connection to a drain hose so that if the diaphragm became torn or punctured the fuel would exit via the drain instead of running down the vacuum line to the carb and flooding that cylinder.