Small Engines (Lawn Mowers, etc.): Snow Thrower vibrates excessively, craftsman snowthrower, belts and pulleys

Question
I have a Craftsman Snowthrower 5HP/Single Stage which vibrates excessively after starting it.

It will run like this with full choke in place and also after moving it off.  It runs about a minute or two and then dies.  It also backfires when trying to start it.  
I replaced the spark plug however,
-the vibration is still extremently high
-it cuts off after two minutes and
-it still backfires when trying to start it.

Now I have to say that last year I did not remove the little fuel from the SB.  I left it in until the next winter.  I have not had any problems with it before this.  What do you think the problem is and how can I correct this?

Thank for your help.
Post this question on the Message Board)


Answer
Hi Sharper,

This is confusing.   You may have one or two problems. The running only on choke problem, indicates a lack of fuel flow.  Probably due to storage with old fuel inside.  The vibrating and backfiring could be a timing or valve problem or ??.  

The carb most likely has dirt, debris or gummed fuel inside.  You will need to remove the carb, disassemble it, clean all the small internal openings and blow it out with compressed air.   Probe each and every hole with a small wire.  

Do a compression test to check the valves.  

Check the belts and pulleys.  If it still vibrates, I would suspect internal damage.

Let me know how you make out.
Michael