Small Engines (Lawn Mowers, etc.): Husqvarna rider w/B&S engine shuts down, Engine Stall under load.

Question
Husqvarna riding mower has a 23 hp Briggs & Stratton Intek V-Twin engine. Runs somewhere between 15 mintues to an hour then abruptly hesitates/sputters and stops. Might be able to restart after a minute or two working the choke.  Then, might run short time (10-15 minutes) or longer (up to around 30-45 minutes) and shut down again.  Or, on the warm engine re-start engine will immediately cycle/hunt a few times then shut down. After engine has cooled, it easily starts and will run for another 30 minutes or so with no problem but then shuts down again.  Is something overheating, causing it to shut down? Thinking there might be a vapor lock, I've loosened/opened the gas cap a few times while mowing, but it will still shut down.  Also, in experimenting, I've set a concrete block on the seat and let it run with the blade on and it runs forever with no problem (I stopped in at 1-1/2 hours).  So, it seems the problem occurs only when the transmission is engaged (hydrostatic trans).  Any thoughts on what the problem could be. Does Husqvarna have a problem with some sort of switch or other component apart from the engine that would shut it down.  It has a new air filter, pre-cleaner, plugs, and fuel filter.  Shop tells me the engine, plugs, ignition coils, etc., check out OK and they can't get it to shut off for them (because they ain't riding it!).

B&S Intek V-Twin Engine Model:  445577,  Type: 0755E1, Code 061205Y-G

Thank you for your time -

Ron


Answer
Hi Ron,

Re; Intermittent Engine problems

First, you provided a well written account of these intermittent problems. Unfortunately these are most difficult to solve.  The governor acts to respond to changes in the load on the engine. When the load increases or decreases the Governor responds by opening or closing the throttle.  This problem you've described sounds like it might be related to this.  

The hunting or surging you've described needs to be isolated to being the result of malfunctions of the Carburetor or Governor.

1. See that Springs - Linkages are moving well (easily) and the governor spring is properly inserted. If you have a mechanical governor then do a static governor adjustment.  Briggs & Stratton Small Engine Care & Repair (page 82).

2. Try to run your engine at various speed settings to see when the (hunting - fuel mixture likely is the cause of problem.  
There might be air leak or obstruction > carburetor causing air-fuel mixture to be uneven.
If so, > take carburetor off for service & or repairs.

3.  Engines sometimes have separate governed idle, spring and governed idle adjusting screw to prevent stalls under light loads.  If (hunting - surging occurs under light loads) look for idle speed screw, (a stop screw on top of carb).  This screw stops throttle from closing fully .  Hold throttle lever against idle speed screw and run the governed idle speed higher by turning the screw clockwise.  Determine if hunting / surging stops, replace idle spring and linkage.  Reset the governed idle speed.  If hunting - surging continues, then clean and adjust the carburetor.

I hope that this information proves helpful.

Howard
PS. I am not aware of any particular issues Husquvarna has with these machines.