You have found one of the "truths" about pull start lawn mower engines! They do not like cold weather! They are designed for warm weather! Grass doesn't grow in cold weather-therefore, no need to start the mower! Simple, huh?
Better just run it dry, and store it away til spring! Or, add some Sta-bil to the tank, slosh it around some, then put it away! A torpedo heater will warm it up, if ya really have to use it, but be careful! And, a clothes dryer sheet stuffed around the engine, will discoutage mousies from using your mower for an apartment!

Think about the last time you bought new fuel. The stuff starts and runs better if the gas is less than 4-6 weeks old. Lots of times I see gas bought mid-summer just doesn't cut it when it gets cool. If it is difficult to crank, 10w30 rather than straight 30 would be helpful. If course, it is good to know that the choke is fully closing, the air filter clean and the spark plug is new.

If it is convenient, you can set up a 60 watt light bulb, incandescent type, not a compact fluorescent, so that the carburetor is warmed. The light should be about one foot from the mower, to avoid overheating. The engine should be ready to start after one hour of this treatment. However, if the lamp is far enough from the engine, you can forget to check it, and nothing bad will happen. Use a 120 watt heat lamp, and set it too close to the engine, & you could have a fire.

still have lots of leaves to grind up. october was brutal this year. probably 50deg on average and 20 days of rain. i have gotten fresh gas about every 6 weeks this summer. i only get a small amount each time. pretty weak summer too. long periods of dry weather and a few weeks where i did not mow too. and now the pull handle cord snapped.

If it started in the summer, and not now, easily, I'd say you should switch to 10W-30 for this cool weather, as suggested above.

i tried syn 5w-30 in my snowblower last year. only blew 2-3 times. starting effort was marginally better. the mower is a 33" troybilt walkbehind. the blades do not turn during starting. pulls over fine. just no start. yes, i use 30w oil.

The Tecumseh carbs seem to have problems with the jets varnishing over. Pull off the bottom bowl nut and check the holes shown in the pictures below for varnish.

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