All Merry Tillers had four stroke engines and those with B & S engines had hardened valve seats, so normal petrol is fine except that E10 absorbs water so, if left for a long time in the tank, water forms along the bottom, which is where the pickup pipe sucks from. So best to use Super unleaded if you are not going to use all the fuel in one session.
If it has the original engine it will probably be B & S and they had points until about 1984. These fir up if the machine is left unused for a while. The little plastic pushrod that opens them can also stick. Check for a spark before trying anything else. If you are getting a spark, the engines with fuel tank under the carb need fuel pumping up into a chamber just under the carb, so these are best started with a full fuel tank to avoid lots of pulls while the pump lifts fuel into the chamber. A teaspoon of fuel down the air intake can be used instead, the engine splutters into life and lifts fuel into the chamber, though probably not enough to keep running at your first attempt. The kill mechanism for the spark is operated when you shut the throttle fully, so be sure the throttle is partly open when starting, often fully open with full choke, works best. All this assumes the original engine. Replacements may be "contactless" and use a different "STOP" mechanism.
