Your 1973 Honda CB750 starts and runs great but when you put it in gear it dies why is that?

Not sure if this model motorcycle has a kickstand switch, but if it does, it may be shorting out even though you put the stand up. The other possibility is your clutch needs adjusting, if it is dying with the clutch pulled in and you put it into gear...adjust your clutch cable accordingly...per your manual or dealer specs. try turning ur idleing up or check ur timing belt. if its carborated then u need a new carborator and that will run u about 3 to 4 hundred dollars. depending on the year.