Do not have to weld your crank now, not until more major engine modification.
There is plenty of modifications that can be done. All depends on what you are wanting performance wise, and of course the almighty $$$$
Upgrading the stock reeds would definately give you imporvement over stock.
Assuming that you are looking at performance mods....you could
Advance timing,
Change gearing,
Lighten Flywheel,
Aftermarket head (or mod the stock one)