***"got 15 mintes out of it"***
Consistent with a clogged vent on the fuel tank cap.
You can simply loosen the cap when the power fades and stuttering begins to test whether the cap vent is the culprit.
If removing and reseating the cap restores good performance at once, the cap vent is clogged and needs to be probed out with a paper clip or other stiff wire. Blow compressed air through the cap vent also (if you have compressed air).

@ rcbe:

917.289031

runs fine with brake depressed. took seat switch out held it down, same, ran fine, remounted into seat, same... engaged blades, croaked. what is cl switch?

@ mowie

removed cap and blew thru it. it was hard to get air thru it (at first). bottom of cap has rubber gasket with donut ring and three air holes. got is so i could blow thru and take air in. replaced cap. i was able to get if going and fiddle with needle valve and after a few backfires it kept going. was able to stay on seat and play with valve while running until it ran pretty smooth for a good five minutes. as soon as i engaged the blades (while still in neutral), it sputtered/shuddered and died. i might remove deck tomorrow night/check belts...

thankd you both for your help

Are the deck pulleys in good condition; not seizing or binding? Often, I've found this to be caused by dirt in the carburetor jet.

My neighbour had the same problem with hers. I had taken the deck off and gave it a good cleaning, top and bottom. It needed it. Too much grass was built up on deck. Plus lubricated the pulleys with WD-40.

I'm having the same problem. The first thing I checked was the deck pulleys. Sure enough I had an idler pulley that was locked up. Got a new one cleaned the underside of the deck installed the belt fired it up pulled the PTO and down the engine went. It would still run but at less than optimal speed and if you actually tried to cut grass it would pull the engine down until it stalled. I put it back into the garage and started with the fuel system. Replaced the filter and checked for good output from the pump, it was very good. Pulled the plate off the top of the carb to check for foreign matter in any of the fuel journals, zip. I pulled both plugs and the left on was fairly black though not oily and caked with carbon. Replaced that plug and checked for good spark-none. Bad coil pack? Got a new on and used emery cloth on the flywheel. Still no spark at the plug. However if while the engine is running I short out the plug lead the engine slows down even more and runs just like you would expect with a plug shorted out. I still don't understand why there is no spark in the plug gap. I have observed the engine running looking for an errant spark in the wiring. Don't see any. Any body got a god idea what to do next? BTW the compression in that cylinder is 150. Now what?

Hello; This may be a long shot but my neighbors mower was doing the same thing. I finally took the carb apart and cleaned it. This seems to have solved the dying when engaging the blades issue. We still have some other issues to fix before a good test mow can be done. I have had to clean out a few old mower and weedeater carbs lately. I suspect the ethanol in the gas may be in some way at least partly responsible. I bought some fuel stabilizer specified for ethanol fuels but have not burned all of my can of the gas treated with the old stablizer just yet.

Fixed jet carbs are a PITA but thats the way it is. Buy a "Weld TIP Cleaner" and do a good job of probing and pokeing every hole in the carb and blowing it out. Tip cleaners have 10+ different diameter wires suitable for every size hole in your carb.

Agree with "weld tip cleaner" suggestion. I have used one for many years when cleaning small openings in carbs, welding tips and also many other small openings. Be cautious when blowing out a carb with compressed air. Cleaning fluids have a way of squirting out at unexpected angles and can hit your face and eyes. Also if you have left some small part in a cavity it can be blown away never to be found again. I sometimes place a cloth in a deep bowl and blow the carb parts inside that with very gentle air at first.

Might also try the interlock safety switch. On a craftsman riding mower it is Inside the engine compartment. Blade engagement lever has a tab that presses down on it. If switch is shorted and blades are engauged, the engine will die.

The contact surface on my flywheel that contacts the ignition coils was rusty. Removed rust, VIOLA! Purrs like a kitten. Lower deck engages with no drain on engine of sputter. Just sayin.