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Hey folks, this is my first post and hopefully someone can help me out. I am 34 and not very familiar with engine repair of any kind. However, I am very mechanically inclined and can pretty much disassemble, repair, and correctly reassemble anything I put my mind to.

Now for the problem. I have recently purchased a Poulan Pro 131 31cc heavy duty straight shaft trimmer from Goodwill for the very high price of $12.99, I figured at that price why not take a chance, what could it hurt. After getting it home and looking at it I saw that the fuel lines were done for. I replaced them with a kit from Lowes. The trimmer started right up. I stopped it and restarted it right away with no problems. I stopped it again and let it sit for a few minutes while I cleaned up the head. Tried to restart it...no go. I double checked to make sure the fuel lines weren't kinked and they were fine. I delved further into the engine, foreign territory. I paid very close attention to how things went and snapped pictures along the way.The carb looked clean but I took it apart to clean it anyway. It was spotless in every way, the diaphragms even looked new and flexed just fine. I delved further, the spark plug had a little buildup on it but sparked fine. The cam and piston moved freely and the piston was clean. The cylinder was spotless, no scratches to be seen, though I didn't disassemble any further on that part. The muffler was clean with no buildup whatsoever. There is no spark arrestor screen over the spark plug, but there is a screen in the muffler that I assume acted in the same way, it had no buildup either. Pretty much everything looked practically new. I reassembled everything correctly according to my memory and the pictures I took. The engine will start right up when it is cold, however, if I stop it for any reason, it will NOT restart until the engine is cold again, usually an hour later. I have fiddled with the two screws on the carb while it was running in order to get the idle smooth and the acceleration (right word?) smooth. Now, the fuel/oil mix is just barely oil rich, I mixed 4 ounces of oil into 1.25 gallons of new, clean gas, trying for a 40:1 mix like the trimmer stated.

Now, like I said, the engine starts fine when cold, but will not restart when hot. I only have 30 bucks invested in this thing, but I really want to get it running. I can't afford a new trimmer and I hate my dad's battery powered Black and Decker. With all of the above in consideration, what else can I do, or needs to be done, to get this thing running?

If I remember right it is 3.2 oz to 1 gallons of gas. Put a little more gas in and try again. Add 32 oz more gas for 40:1 some engines are very touchy. Also chuck bulb for leak.

If it starts un assisted cold, but not warm I would look to the coil. Get it hot and whiles its hot check for spark you probably won't have any and will need a new coil

Update...

So, after retesting the spark plug, I found I was getting a weak irregular spark. I replaced the plug with a new one and tightened everything, all the bolts on the trimmer, down nice and tight. Filled it with gas and after fiddling with the screws on the carb a little, one full rotation from a gentle tight on the screw (idle) and 1/2 turn from a gentle tight on the orange cap (throttle), it started right up. I stopped it and it restarted just fine. I stopped it again after letting it warm up, went and changed shoes, came back out and it restarted with no problems. I trimmed the entire back yard with it. Then I stopped it and tried to restart it. After a number of tries it started back up. I fiddled with the screws a bit to try and reduce the idle a tiny bit, stopped it and it wouldn't restart without resetting the screws back to a full turn and a half turn. I stopped it again, tried to restart it and fuel just came running out of the choke on the carb. I had to drain the gas to get it to stop. None of the hoses had come undone, no bolts were loose, the carb was tight up against the diaphragm and the piece it bolts to. I couldn't find any reason why it was dumping fuel. The only thing different was that it was low on fuel and the fuel filter was not completely submerged.

In case it helps, here are pics of the ID tag and the Walbro carb model number.




Now, what does slender white smoke snaking out of the choke and downward mean? That happened after repeatedly starting it and having it die. I was carefully adjusting the screws every time it died, then it wouldn't restart period and the smoke started snaking out. It did it the other day as well. There was no gas pouring out this time though. BTW, I broke down the carb, cleaned it, removed the needle valve and cleaned it. I made sure all the diaphragms were flexible and reinstalled correctly.