UK '98 GS500 Only firing on one cylinder, bogs and dies after 1/4 throttle

[NapalmMachete]

Hello, I have been cleaning up my '98 GS500 after sitting for a year over the pandemic and it currently only runs on the right cylinder. Anything after 1/4 throttle and the bike bogs and dies. I have scoured the internet, forums, and manuals for ways to isolate the issue with no success.

Things I've tried:

- Charged the battery.
- Cleaned the carbs (multiple times).
- Replaced the jets with standard UK sizes and the needle clips to the 3rd slot.
- Set the fuel/air mixture screws to 2 1/2 turns out.
- Emptied the tank and filled up with fresh, premium fuel.
- Replaced all of the rubber parts (carb boots, diaphragms, seals, etc) with official Suzuki parts.
- Checked the valve clearances - all within spec.
- Replaced the spark plugs.
- Checked the ignition coils, cables and boots with a multimeter - all within spec.
- Swapped the ignition coils, cables and boots (left to right, right to left) - problem persists on the left-hand side.
- Run without airbox fitted - no change.
- Blocked air intakes separately while running the engine - no change to the left-hand side, engine dies blocking the right-hand side. Interestingly, the cardboard I used to block each side got sprayed with fuel on both sides.
- Unplugged the spark plug boots while running the engine - no change to the left-hand side, engine dies pulling the right-hand side. Interestingly, I get an electric shock from the frame/tank when the left-hand spark plug boot is disconnected.
- I've checked the earth wire to the negative terminal and all seems OK
- I've followed Kerry's (?) guide to checking the signal generator wiring with a multimeter - everything is within spec.

Logically, I believe I've ruled out air and fuel as fine, and it's likely something to do with the shorting on the frame.

I feel I've been extensive in my testing and it's starting to get frustrating so any suggestions would be greatly appreciated 

Cheers

[Bluesmudge]

Have you checked the fuel level on the carbs? Try running clear tubing up from the drain tube and see if the gas levels out to be at or just below the float bowl gasket when you open the drain screw.

Since the coils and boots test well with a multimeter and swapping them makes it persist on the left side, I'm guessing its still something to do with the carb.

[mr72]

It's definitely carbs. I'll let the others chime in about the cause. But since you've had it apart and done lots of work, the likely thing is some accidental mis-assembly happened along the way.

[Suzukirider74]

Have you measured the compression in the cylinders?