So my blue GS needed a carb cleaning job and since the bike is far away from Lahore so obviously I did not have the option to take it to my mechanic and get the job done easily, so time for a DIY attempt.
On my previous bike, the FZR, I had opened up the fuel tank so many times without much problem but the same job with a GS500 is a bit more complex thanks to the fuel key system of the bike which does not come with the "Off" option. To reach the carbs we have to remove the tank first and in fact, getting the tank removed is what gave me a bit of a tough time, so here is how I managed it.
Step 1. Remove the seat
Step 2. Remove the tail
Step 3. Open the tank bolts/nuts located on each side of the main frame
Step 4. Open the fuel key bolt so the key hangs loose.
Step 5. Raise the tank rear end a little bit and put some support under it so you can reach the screw under the tank and turn the screw to "off" position to cut the fuel flow from tank to carbs.
Step 6. Take out the Air Filter box.
Step 7. Loosen the clamps holding the carbs to the engine and pull out the carbs.
Step 8. Take out the throttle and choke wires. This will detach carbs from the bike.
Step 9. Carb cleaning.. Since I did not need to adjust the mixture so simple cleaning is not too much of a task, however when you open the main jets you may need new small O rings so the jets sit back properly so do not open the jets unless you have got a pair of the exact size with you. Clean the jets with fuel, nothing big.
Step 10. Put back the carbs and repeat the above steps inverse. Job done
Posting some pics below..
Here is the fuel key after removing from the bike:
I do not know if some other bikes follow the same technique but Suzuki's old models like GS500, 750 and 1000 have a similar fuel key. Options available on the fuel key are On, Prime and Reserve and no Off option. While removing the pipes make sure you memorize well which pipe goes where else there will be problems 
