Small Engines (Lawn Mowers, etc.): One Problem Leads to another, fly wheel, fuel compression

Question
Hi Michael
I pulled the fly wheel off my briggs 3.5   engine as you suggested and found the flywheel key to be in good shape with no dammage. It has not done the strange   carburator thing since i last emailed you but still refuses to start. I suspect a carb problem so I decided instead of riping the carb to peices and checking everything i switched the carb and fuel tank assemblies with yet another engine of the same make that doesnt run thinking that assembly would work. there are some  of life mainly a loud crack followed by some exhaust smoke but it won't start. The engine is getting air, fuel, compression and spark. Do you think that perhaps the screw that adjusts the amount of fuel in to the carb needs adjusting? The carb is one of those diaphram ones mounted on the fuel tank. If it continues to put up a fight starting would you think a carb cleaning would be in order or could there be a more serious problem?
thanks, Dan

Answer
Hi Dan,

If you have good spark at the plug, then the problem is most likely fuel flow.  I forget our past mailings but try squirting fuel into the carb and see if it will start and stay running as long as you add fuel.  If so then the carb is blocked with dirt or gummed fuel.  Check the screen at the bottom of the carb's in-tank fuel inlet tube.  If okay, I would add a carb rebuild kit which would include a new diaphram.  The large fuel mixture screw is initially set at 1 & 1/2 turns out.

Keep me posted.
Michael