Just clicked on this thread for the first time and I see several things happening.
1. In the original post, you "flipped the petcock to on". These petcock don't have a position called "ON". They do, however, have one called "RUN", which is with the lever pointing straight down. THAT is where the petcock should be about 99.9% of the time. If you are running low on fuel, rotate the lever clockwise, so it is pointing forward to the REServe position, you will be able to use the last gallon or so in the tank while you find a gas station. In both of those positions, a properly-operating petcock will flow fuel when the engine is running and stop flow when the engine is stopped. If you rotate the lever fully anti-clockwise to the PRIme position, fuel will free-flow. This is only used if you have not ridden your bike for several weeks or have drained the float bowls for some other reason. If you use the PRIme position without the engine running, it is possible to overpower weak float valves and cause some overflow.
2. Terminology. What is the "needle at the bottom of the carb"? The only two needles that I know of are the float needle, which is
inside the carb and allows gas to fill the float bowls and the needle that goes up the middle (also inside the carb) to control fuel flow through the needle jet for mid-range fuel metering. There are no needles visible from the outside.
3. You "need a picture book"? Click
HERE for your picture book.
4. You "tapped the carbs, now no gas flow". If it was a stuck float valve, tapping on the carbs will sometimes dislodge the problem, allowing the float valve to work properly. When the bowls are filled to the proper height, no more gas will flow until the engine uses some or you wait long enough for some to evaporate.
4. There is a "cheap fuel filter" installed. Why? You said you had just lined the tank, it should be CLEAN now. There is a filter on the petcock that should take care of everything downstream. Too many times, an
automotive fuel filter is installed. The problem with those is that they are designed to be used with cars that have fuel pumps. A fuel pump will push fuel through the rather restrictive filter media. We have gravity-fed systems that do not generate enough pressure to do that. If you insist on using an external filter, go to Lowe's, Home Depot, Auto Zone, wherever, get a filter for a lawn tractor. Most of them also have gravity-fed fuel systems.
5. Your '79 bike should have the VM carbs. As mentioned, the VM carbs have a cap that is sort of a domed rectangle that is held on with three small screws. The '80-and-newer four-cylinder GSes came with what are known as "CV" carbs. They have a much larger cap that is square-ish with a raised round dome inside the four cap screws.
What to the initials stand for? VM is the model name of the carb. Your carbs should be VM26SS for the full name. "CV" is actually a
type of carb, and it stands for "Constant Velocity", referring to the way a vacuum-operated slide controls the velocity of the air over the jets. If you wanted to refer to them the same way as the VM carbs, you should call them "BS" carbs, for their model name. The '80 750s came with BS32SS carbs.
There were many other manufacturers that also made CV-style carbs, each, of course, had their own model name for them, so it just seems a bit strange to me that we refer to one model by its name and the other model by the way it works.
6. You installed pods. Hopefully, they are better than the cheap EMGO pods, but somehow, I doubt that. Either way, I hope you have re-jetted the carbs for the pods.
7. You are "standing on the right side of the bike... Where do these little valves need to be going? " What "little valves"?
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