1970 Eska Snowblower won't stay running

[62monterey]

1970 Eska Sno-Flyr with 5hp Tecumseh engine. Model #936. Serial #51897.

I bought it earlier this year. I cleaned it up, lubed the chains, replaced fuel filter, checked the spark plug, and ran it several times over the summer to make sure it was in good working order. Never faulted.

Now it doesn't want to run properly. Starts good at 1/4 throttle and 1/2 choke. However, when throttled up to blow snow, it will stumble and drop RPM. If the choke is set at 3/4, it will run mid to high RPM fine for a short time before stumbling. Fuel is flowing properly.

All information to solve this issue is greatly appreciated. Thanks.

 

[mechanic mark]

Tecumseh Service Manuals Check air filter for replacement.

"K&T Parts House Lawn Mower Parts and Chain Saw & Trimmer Parts"

Adjust your valves per specs., make sure you're using correct OEM spark plug as listed and gaped to specs.

 

[62monterey]

No air filter on this one. My 2003 Craftsman snow blower (with 5hp Tecumseh) doesn't have one, either.

Tons of info in that link. Thanks.