Small Engines (Lawn Mowers, etc.): Toro Snow Thrower starts hard / runs rough, wear eye protection, free cloths

Question
Ben,

I have a Toro S-620 2 cycle snow thrower that is about 12 years old (model 38165).  Over the past couple of years, it has been progressively harder to start.  Once started, the engine revs up and down and stalls under heavier loads.  After it has run for awhile, it has less of a tendency to stall.  Something new this year is that as I back the choke off, it wants to stall also and has trouble handling any sort of load.  So far this year, I have only been able to keep it running by keeping the choke turned all the way on.  The spark plug was last replaced quite some time ago (about 6 years ago, I think).  Does it sound like I just need a new spark plug or do you think I have carburetor issues or other issues?

Thanks for any insight you can provide.
Bruce

Answer
Bruce
Condition of gasoline: Old or contaminated gas will make any engine harder to start. If the problem is with an engine using last year's gas, drain the old gas completely and dry out the residue in the fuel tank if possible. If debris or water is found in the old gas, the carburetor may need to be drained and cleaned as well. Then add fresh gas (not from the batch sitting in the can since last year!). In cold weather, the water can turn to ice inside the carburetor float bowl causing all sorts of problems including flooding of the engine. This problem sounds like a carburetor This is what you need to do.

Cleaning the carburetor parts
Use carburetor cleaner and lint free cloths or paper towels to remove all built up brown or green gunk, varnish, and other contamination from the metallic parts. Pay particular attention to the machined passages and metering holes.
WARNING: Carburetor cleaner is both flammable and the fumes are toxic. Do all cleaning away from open flames and outdoors if possible. Wear eye protection. The stuff will also eat plastics including some plastic eyeglass lenses.

Take care where non-metallic parts are still in place as extended contact with harsh solvents may degrade their properties (inlet seat and primer bulb, if present). Low pressure compressed air may be used to blow out passages but only use this on the fuel line from inside the carburetor body - else you may end up with the inlet seat clear across the driveway never to be found again.

DO NOT use wires or metal instruments to clear any of the passages as their size is critical.

The small hole in the hollow bolt on the bottom is most critical. Make sure it is cleaned down to the shiny brass and that this hole is unblocked and fully open:
GOOD LUCK REPLACE THE SPARK PLUG EVERY YEAR ALSO THEY ARE CHEAP AND KEEP THE ENGINE RUNNING