Tecumseh HM80 on coleman generator. won"t stabilize, backfires. new plug, fresh gas 'carb cleaned. starts first time'new air filter. any suggestions?

Replace spark plug. Replace air filter. Fill oil. 30w. When plug is removed pull rope several times to blow out cylinder. With air filter removed spray starter fluid into air intake hole of air filter, try to start.
Ensure fresh gas only is in gas tank. Always add Stabil to gas. If no start clean carb or replace. carb.

Clean or change air filter. Clean, gap or change spark plug. Empty gas tank add fresh gas with Stabil. When spark plug is removed pull rope several times to blow out cylinder. Spray starter fluid in spark plug hole before replacing spark plug. Clean outside of carb so choke works freely. Spray starter fluid into carb breather hole with air filter removed and try to start. if running replace air filter and cover. If no start disassemble carb and clean. If no start replace carb.

I have a Coleman Powermate 5000 with 10 HP Tecumseh engine. It is very hard to get started. once started runs great . But when you shut it off and try to restart it it will not start.
I have plenty of fire. I also replace the carb.
I still have problems getting it started. I tried to start it with out the filter also. What can i try next?

Thanks for any help

try sanding the magneto and adjust the fuel air mixture screw till it smooths out

plugged carb

I have an HM100 on a 5500 watt gen with the same problem. This motor calls for a J17 spark plug, but I found using a J19 (hotter) plug solved the problem. I think the J17 doesn't get hot enough for a complete combustion burn so it act like fuel starvation thus resulting in the black sooty and wet plug.

Check the air filter.

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Sound like you've done things in the correct order, tecumseh's are notorious for carb problems if you let as sit in them. Backfiring is timing related (flywheel key) or valve problems. I would take a closer look at the exhaust valve I don't believe it is closing all the way.

Sounds like the timing may be off or maybethe exhaust valve maybe hanging open.

To maybe convert your Flamethrower back to a generator, Make sure the fuel line is a good quality thick rubber material (like OEM )since it passes through the engine,HEAT is a issue, if it has been modified to steel, or it's thin rubber, it will overheat the fuel on its way to the carb and cause backfires after the engine warms up , ( vaporizing gas and pressure bypassing the jets flooding the engine) I use 1/4 inch Goodyear sold at Autozone , one of very few name brand quality parts you can get there. The other possible cause is carbon deposits built up on the leading edge of the valve not allowing the valve to close all the way, just clean the valve, it is caused by too lean or rich carb setting or clogged jets, if it is a newer style carb with a pink main jet then debris in this area will always cause backfire, check and make sure the old tiny O-ring on this jet is not still in the bottom of the shaft, people forget to pull them out all the time or give up trying to pull them out, I use a paper clip and bend the end 1/8 of a inch @ 90 degrees to fish hook it out of there, CLEAN THE SHAFT with carb cleaner and a Q-tip.... A Tecumseh engine will always backfire if the carb or airflow is not perfect and sealed tight !!!!!! it looks simple to rebuild the carb but you must take your time and look close, clean it very well, make sure the jet is SEATED properly and all tiny holes are clean, use guitar string not torch head cleaners as they will enlarge the holes and make your carb run rich.