I don’t have a manual for your motor but I’m betting the .073″ dimension you were given is for the piston height before top dead centre. Most small engines such as found on lawn mowers and chainsaws set the ignition timing by this method. Obviously, the points will have to be gapped correctly first before measuring the piston height. Points are usually set at .015 – ,020. depending on the make and model of the motor being worked on.
You might want to contact a Tecumseh repair shop as special tools are required for this job. If you have a dial indicator and a degree wheel, you should be able to do it yourself no problem.
