@Imola Nice first post it might be worth heading over to the bar and say hello .
As for the 2nd gear issue
The problem only affected a few k2 bikes(Suzuki upgraded the gear on later bikes )
Do you have a problem the 2nd gear issue made it jump out of gear .
Other things that can a
Effect the gear box are wrong oil,
Sticking clutch slave cylinder and or pushrod and gear leaver being fitted in the wrong postion
If your taking the gear box out it might be easier,cheaper and better long term fitting a 2nd hand k5 onward gearbox .
Good luck
