1250 Engine Trouble

[dwhipple]

Looking for a little help with a 1250 Quiet line Cub. The trouble is with the engine. I can start the engine and engage the mower deck and let it sit in place and it will run fine but, I start mowing and after driving about 60 feet the engine will sputter then just shut down. I can restart the engine right away, but when mowing it will still shut down. I have replaced the points and condenser and it is still doing the same thing. Please email me at: apollo57@ptd.net Any help would be appreciated.
Thank You

[ksanders]

Coil can possibly do that. Usually takes a bit longer though. Poor fuel flow to carburetor? I've had more quietline than anything with sticky exhaust valves with similar symptoms. I'm guessing the shielding traps more heat and is tougher on valves?

[dwhipple]

I cleaned and rebuilt the carb, changed the fuel filter and replaced the spark plug when the problem first began. I know the older "K Series " engines had valve adjustment issues is it possible that could be the issue?

[Klapatta]

If you are running an inline fuel filter bypass it. I have experienced both fuel starvation and over pressurization blowing open the carb float while at rest using them.

[ksanders]

+1 on the fuel filter. I was talking more about valves sticking than the adjustment of the valves

[dwhipple]

Ok guys, I'm still having trouble with my 1250 K301AQS engine. I have replaced the coil, points and condenser. I have also removed the fuel filter ran a fuel line from the tank directly to the carburetor, warmed the engine and readjusted the carburetor. I then started mowing my grass, mowed for about 70 feet and the engine shuts down. It didn't sputter or backfire. Cranked the engine and it started right back up at idle but for some reason, even with the engine warmed up, it will not start up with the throttle opened without choking the engine. After restarting the engine, I managed to mow some more and this time before it shut down the engine was hesitating (like a miss fire) this time. I don't have the money to take it to a repair shop for a major overhaul right now so I'm trying to fix it myself. Any help would be appreciated to get it properly running.

Thank You

[dag1450]

I'm sure this is frustrating. Sounds like it's starving. Have you checked the fuel flow out of the tank with the new fuel lines? It should flow pretty good. Cap on or off should be similar. Could be cruddy down on the screen in the tank. If you have good flow then I would look for another carb or clean it again. I really like the 2+2 carb cleaner along with compressed air. I have no idea of your carb skills ...if their not super strong maybe watch a couple videos on proper clean and assembly. Please let us know about the flow.…

[davis2]

Dave, could it possibly be related to a loose ground wire/bad ignition switch?

[Bsmith]

I had a similar problem with a 1000 quietline. Would die out while mowing. It would lose power and then die out. If I sat on the tractor for a bit while the engine cooled I could hear a slight pop. It was the exhaust valve sticking and popping back into place. I started giving the gas and the oil strong doses of Marvel Mystery Oil. This stopped the valve from sticking and I mowed with the tractor for a few more years before selling. If the valve would have continued to stick, I would have pulled the head and redid the valves. Please try the Marvel Mystery Oil and see if it helps. If not it may be time for a valve job.

[BigMike]

Is the gas cap vented?
As soon as it dies look at the fuel tank and unscrew the cap and see if it expands.