How to start the gsxr 750 after running out off

Question edited to add full 'year maker model'.

Code 21

https://www.google.com/search?q=2008+Suzuki+GSXR-750.+Error+Code+C21

All about Code 29

https://www.google.com/search?q=2008+Suzuki+GSXR-750.+Error+Code+C29

..

have you checked the carbs are clean and all seals are good ? floats float if you put in a jar of fuel ?

Check sidestand and clutch lever lockout switches...

so you can fix the fule tap if it ever starts to leak?

Hi ,
The jets in the carbies will have to be replaced as they may have been temped with to give more fuel .
if the seats have been changed , the float will have to be reset as well to avoid too much fuel in the carbies .
The rust in the tank will have to be flushed out by filling it up with fuel and tip the tank out .

try some aero start, starting spray, it may help work out what may be wrong.
Try a compression test
drain the carby bowls.though the little drain screws
Did it stop for any reason or it just wont start after it has sat for a time.?
What have you tried?

Backfiring can occur from many things. First thing I would do is have the timing checked. If the timing hasn't been checked in a while and you ride regularly, it may just be that time. If the timing is fine, you may be running either rich or lean. If you are running lean, it could be from a semi-clogged fuel filter. If the fuel filter is fine, you might just have too much air in comparison to the amount of fuel being delivered. In that case it isn't a serious problem. If it bothers you though, you could install a digital fuel modulator to increase the amount of fuel that is delivered.

Another problem may reside with the intake valves

You left your petcock on, the fuel bowls over filled and the gas went into your crankcase

DON'T START THE BIKE WITH GAS IN THE CRANKCASE YOU WILL BLOW THE MOTOR.

Empty the gas, put in fresh oil, run engine, then change oil and filter again and you are done.

they will more than likely fit but doubt that it'll run smoothly