Crusty; good suggestion. I might try this as well on my mower since it is having a similar problem.
I wanted to throw in my two cents worth on another potential solution to the dying motor (and maybe this is a too simple solution but it helped me): be sure to clean or blow off all the contacts that kill the engine for safety reasons; such as the seat contacts, blade engage, brake, emergency brake, etc. I found that my motor would not crank but cleaned all points and started up.