Small Engines (Lawn Mowers, etc.): Onan 448 stalling, case 448, wits end

Question
Mr. Bridgers,

I saw a posting you gave to Phyllis back in June 2006 which is very similar to the problem I am having.

I have a case 448 with an Onan B48M engine.  The mower runs for about 20-30 minutes cutting the grass and then stalls.  I can get the mower restarted fully choked, but as soon as I  close the choke it stalls again.  Running under choke is not fully powered.  I have drained and blown out the fuel line.  I replaced the condenser and points mechanism.  You suggested to Phyllis having the valves reground and lash reset in the June 2006 posting. Did it fix the problem?  I am about at wits end.  I would like to know if this was the resolution before either I go down this path or a pay someone to do it for me.

Thanks for your time.

Sincerely,

Ethan B.


Answer
Hello Ethan:

Check the Gas Tank Cap and Ensure it is Venting Properly. If the Cap is Not Venting the Tank, a Vacuum Builds Up and Stops the Gas Flow from the Tank. Even with a Fuel Pump this Occurs. It Takes 15 to 30 Minutes for this to Occur in the Tank. Since you are Able to Run the Engine on Choke; I do Not Suspect the Valves being the Cause of this Problem. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John