If your engine is running rough, a problem with the carburetor is a likely cause. Rebuild or replace the carburetor to fix a fuel delivery problem.
A clogged fuel filter will also prevent the engine from getting fuel, causing the engine to sputter or run rough. Check the fuel filter and replace it if clogged.
A dirty spark plug won't ignite the fuel consistently, causing the engine to miss and sputter. Check the spark plug and replace it if necessary.
Incorrect valve lash could cause the engine to run rough so check and adjust the valve lash.
Check the engine sump gasket because a leaking gasket can cause low compression and a rough running engine.
A thorough snowblower tune-up can also help the engine run smoothly.