need some help

[IRISH-RACER-14]

so i bought a 300ex bottom end for 70 but the sprocket is welded on. i plan on putting a few goodies into this motor. should i strip the whole motor and build from the beginning and replace the sprocket shaft? ive never done anything like this before. would it be wise. i plan on buying a service manual to help. what should i do?

[ridein'red7]

carefully cut/ grint the welds until u see a crackwere it was welded and the shaft and hit it with a hammer well tap it easy n it should pop off

[IRISH-RACER-14]

yes ill try that. do you think i should try rebuilding it my self with the help of the service manual and the internet? im 16 and have not done anything like this before. i have done some top end rebuilds on a 2 stroke blaster but that was all. i bought this motor as a project and hope to learn something out of it