Welcome aboard.
What Chinewalker said. As long as the timing belt is aligning the magneto to the flywheel properly, the magneto most likely needs a tune-up. Another thing I found on mine was the carbon button in the magneto cap was sticky because of wear. A new button fixed the sticking.
But let me add this because I had the same situation after replacing a timing belt because I didn't remove the flywheel the correct way.
After putting the flywheel back on with the new belt on the crankshaft timing pulley and leaving the flywheel nut and washer off, remove the top spark plug and turn the flywheel by hand CW until the #1 piston is at top dead center. Also TDC is when the flywheel key is pointed directly at the magneto pulley shaft. Make sure the belt doesn't jam up.
Remove the flange over the magneto timing pulley and find the arrow cast on top of the pulley.
After fitting the belt on the magneto timing pulley, the the cast arrow will point directly at the flywheel key when the flywheel pulley and magneto pulley are aligned at TDC. The cast arrow will also point directly at one of the two timing marks on the flywheel. That's unless you did what I did when I removed the flywheel incorrectly.
Hope that helps some.
