I have a 8 HP snow blower engine that runs smoothly when fully choked, but very poorly with no/part choke?

Even after it has warmed up and would normally die if it was choked, it still runs smoothly. What could be wrong with it?
If it is leaking-in air somewhere, where are the likely points of leakage? Could it even be a head gasket?

When I checked the spark plug, it appeared black a sooty, but maybe that's becasue I've been running it full choke for a while.

Comments

4 Responses to “I have a 8 HP snow blower engine that runs smoothly when fully choked, but very poorly with no/part choke?”
  1. adam/penny says:
    July 22, 2009 at 9:52 pm

    it sounds like the carb is sucking in air somehow, that’s why it’s not shutting off when it’s full choke and is hot.

  2. GTB says:
    July 22, 2009 at 9:52 pm

    This is very odd. You need a fuel rich engine to start because the fuel is insufficiently volatile. As it warms the aerosol of liquid fuel vaporizes and displaces the air needed to support combustion and this is why you release the choke.

    Since your engine does not seem to need extra air, I wonder if you have air leaks into the fuel / air mixture between the choke and the engine itself. There has to be a way for more air to get into the combustion chamber for this to work.

    I suggest you regap the plug or replace and regap if it is worn, check for air leaks, change air filter (if there is one) and see if this eliminates the behavior.

  3. damo1313 says:
    July 22, 2009 at 9:52 pm

    you need to have your carburetor rebuilt. no other way.

  4. Jim W says:
    July 22, 2009 at 9:52 pm

    The carb is not working properly, before you do a rebuild, check the needle valve adjustment, it may be out of proper setting. Typical was 2 to 2 1/2 turns open. Then again it may not have the needle valve so it needs a rebuild.

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