‘75 GT550 carburetor questions

[GTandcbr]

If you intend keeping the bike this tool makes float height an easy task.
https://www.ebay.co.uk/itm/Suzuki-GT750 ... SwnLdWrojv" onclick="window.open(this.href);return false;
Or make one yourself i did

[pgb123]

Ok, so something strange happened. I replaced the petcock with a new one and the fuel leak stopped. Not just the leak from the petcock, but also from the carb overflow tubes! Why would that be?

Also, funny thing. The bike surged at idle. I couldn’t really hear it, but the odometer bounced all over the place. I adjusted the air screws and thought I fixed it. While riding yesterday, the needle started bouncing again. Turned out I didn’t insert the odometer cable correctly when I repaired the gauges. Duh!

[GTandcbr]

Okay the likely source of your overflow problem was that the diaphragm in the petcock was stuck open and therefore petrol continued to flow even when the bike was switched off. Which would be like leaving it in the prime position. Glad to see you have solved some of your problems

[pgb123]

It didn’t flow while the bike was off. The petcock leaked only when it was running. The other issue was that fuel came out of the carb overflow tubes at a pretty steady rate while it was running. I figured I needed to adjust the floats, but when I replaced the petcock, the carb overflow problem disappeared. I just don’t understand why.

In any event, I’ve finally gotten a chance to really ride this bike and it’s awesome!

[GTandcbr]

There are only 2 things in the system to control the fuel flow,the diaphragm in the petcock and the float level needle valves. I suggest that perhaps the needle valves were unseated but sorted themselves with the engine vibrations? Anyhow it's all sorted for you now