Why are their air bubbles in the fuel filter of my GX 345 lawn tractor

SOURCE: Engine starts, but stalls when clutch is released.

The is a safety switch located underneath the mower, in the dashboard area. This switch will not pass voltage to the ignition system unless the pedal is depressed, or the deck is not all the way up. However, your culprit is most likely the pto (power take off) switch on the dash that engages the blades. It will not allow the mower to start, if pulled, and if faulty will shut off ignition power when you release the pedal. First. You'll need a volunteer to sit on the mower and operate the controls.  Now put the deck down and with the pedal depressed start the engine. Nothing should happen, if it does replace the deck switch Sears part number #176138 mentioned above. Now raise the deck and release the pedal. Again, nothing should happen. Same solution if it does. If nothing happens on both tests the switch is ok. NOW. Behind the dash, find the pto switch, and squeeze the sides, depressing two clips that hold it in the dash. You should now be able to slide it though the dash, wiring attached. Unplug the switch. With pedal depressed, deck up, someone sitting on the seat, start the mower. Now release the pedal (making sure to block the wheels and have the transmission handle is in the neutral position. If the engine continues to run, you found the problem. Replace the PTO switch. Sears part number # 174651. Also, check the plug to the pto, ignition and deck switches for corrosion as this is a common problem, though not likely to cause yours, it could. Good luck, and please let us know the outcome, good or bad. Thanks so much.

SOURCE: air in fuel line between fuel filter and injection

Hi, before the pump it is a loose connection or maybe a pin hole in the pipe, check all the connections and pipes for seepage, after the pump it will be a leak, i knowit sounds the same but after the pump the fuel is under pressure. It would appear that your system drawing air rather than forcing air in. daveg

SOURCE: Our new to us john deere 345 tractor won't keep running

You may try blowing backwards from behind the fuel filter into the gas line. Not to much air pressure though. Make sure the gas cap is off.

SOURCE: Stalling Craftsman LT 1000 Lawn Tractor

I have a Craftsman 21 HP Twin riding lawn mower and have replaced both spark plugs, filter and battery. New gas. New Oil....still will not start?? HELP!!!

SOURCE: I have a craftsman 19.5 hp lawn tractor model #

Carb is dirty and leaning out so the governor throttles the engine up & down causing a surge. You can try using a good quality fuel injector cleaner product mixed in the gas. That may help but if that doesn't work it will be best to replace the carb. That is an older engine and the carb is not likely fixable. It is a matter of how much money you want to throw at it. Putting a carb kit in it and giving it a through cleaning has no guarantees then you will still need to spend money on a new carb. The carb for that runs about $165. If you replace it yourself I'd recommend taking pictures as you take it apart so you can see where all the linkages go and you will be able to put it back together without problem. Hope this helps. Please vote yes if you find it helpful.