Small Engines (Lawn Mowers, etc.): engine sputters and bogs when blade is let down, internal passages, riding lawn mower

Question
i have a yard machine, 20 hp 46 inch cut riding lawn mower. When i let the blade down to cut its bogs down and tries to shut down. it does not matter if it is warm or cold.i have cleaned the spark plugs and air cleaner. the lawn mower runs very good when the blade is not down. any help would be appreciated.

Answer
It sounds like either the engine needs more fuel or there is a problem with the seat safety switch.  If equipped, try opening the high speed mixture screw 1/8 of a turn at a time to enrichen the mixture.  If this has no effect or the carburetor has no adjustment, you will need to clean the carb thoroughly, including pushing a piece of tag wire through all of the internal passages.  If the carb is not the problem and the engine is shutting off as opposed to bogging down, try bypassing the seat safety switch with a jumper wire.  If this corrects the problem the switch will need to be replaced or adjusted.  Do not continue to operate with the switch bypassed.  Hope this helps.