Id reccomend pulling the cover off the valve chest and checking the clearances.
Its not hard to reset them if needed. A screwdriver and a bench grinder is all you need. If you want me to write something up to run you through it i can.
You can buy a cheap set of valve spinners, (wooden handle with a suction cup on the end) big one and a small one. And a tube of valve grinding paste. Its not hard to do.
Its never a bad idea, i pull the head off all the older mowers, You cant check to see how good the rings are but you can get a look at the bore and it does not matter how much messing and tuning you do if the bore is no good you wont fix the motor to a point where its worth having.
