Small Engines (Lawn Mowers, etc.): question on craftman rotary lawn mower: gasoline leaks and wont start, carburetor body, gasoline tank

Question

front of lawn mower Dear John,
I got a second hand 6.75HP propelled lawn mower (model # 917.37657), which was bought in 2005 but I never tried it until last weekend (the seller told me it was functional). I changed the oil and filled the gasoline tank. The problem is that the gasoline leaks out from the from a rubber "nob" in the front, inside the red circle in the attached picture. I can see the gasoline bubbles out from a pinhole. Will replacing the rubber cup helps or it supposes to have the pin-hole there? Please advice.
Thanks. Deli

Answer
Hello Deli:

Replacing the Primer Bulb is Required, but Will Not Solve the Problem. You Need to  Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl, Float Pin, Float (if Applicable)  and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. The Carburetor Float Needle has Stuck and Requires Cleaning. When this Happens, the Carburetor Really Needs to be Soaked and Cleaned. If this Engine is a Tecumseh (will have Model Numbers like:143.XXXXXX); You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.outdoordistributors.com/ and Select the T. Then Select Tecumseh. Then Select Don't have Part Numbers. Then Enter the Model Numbers. Then Select your Model and Download the File for Online Viewing. If this Engine is a Driggs and Stratton (will have Model Numbers Like 125K02 - 0500-E1); You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model (5 or 6 Digits) and Type Numbers (first 4 digits Only). Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. Have a Happy Holiday Season and May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John