Small Engines (Lawn Mowers, etc.): Carburetor, toro 826, fuel mixture

Question
I have a Toro 826 Snow Thrower with a Briggs %26 Stratton 8 hp motor the model # is 190402. The problem is that it will not run unless you hold the choke down in full choke position or slightly up from that from full choke and then it runs full speed never idles. I have adjusted the idle mixture screws and the high speed needle valve screw by turning them in all the all and then backing them out 1 1/2 turns with no change in the out come. When I stated the engine it started right up and  I adjusted the idle mixture in all most all the way the in (it never missed or started to die) engine finally idled and then died. When adjusting the high speed needle valve is ran full speed until it was almost all the way in and then is die (it never missed or slowed down just quit) I have checked the shaft running thur the carburetor and connecting to the magneto it is free and the magneto is in the right position to be at full speed. What is up with this down draft carburetor?

Answer
Hi Paul,  

Check that the gas tank is at least 1/2 full.  See that the gas is reaching the carburetor okay.

Check the setting on the carburetor.  it sounds like you have done this.

The mixture screw controls the flow of gas through the carb.   If the screw is not properly adjusted or damaged this can affect the operation of the engine.

Check the tip of the screw tip see if it is bent or worn.  Don't try to straighten it.  If the o-ring is damaged then you should replace the screw completely.

After checking the screw re-install it (with fingers) and then back it out 1 1/4 turns until it stops.

Start the engine and turn screw clockwise until the engine runs slower.   Fuel mixture will likely be too lean at this point (with engine slowing down).  Turn the screw counterclockwise and see if the engine will run smoothly.  Do this process slowly until you notice an unevenness to the engine operation.

Do the same adjustment for idling.  AFTER SETTING THE LOW-SPEED SETTING - CHECK THE HIGH SPEED SETTING.  THIS CAN BE AFFECTED BY THE IDLE SETTING.  

SOME CARB'S HAVE AN IDLE SPEED ADJUSTMENT SCREW.  

I HOPE THIS INFORMATION HELPS YOU SOLVE THE PROBLEM PAUL,

Regards,

Howard