Snapper mower trouble; please help

Alright, here's the situation. I recently was given a Snapper self-propelled mower. It's in great shape just a little dirty. However, I cannot for the life of me seem to get it to start. I took the carburetor apart and cleaned it with a wire brush and carb cleaner-nothing! I replaced the spark plug-nothing! I made sure it had enough oil-nothing! I checked the fuel lines for leaks-nothing! I replaced the primer bulb-nada!

It seems like no matter what I try I just can't get it to reliably start. The only way to get it to start is by removing the spark plug and putting a small amount of gasoline in the spark plug hole, then putting the spark plug and wire back. Then, and ONLY then will the mower start when I pull the cord. However, it will only run for 2-3 seconds and then promptly cut off. I can't get it to restart after that unless I put more gas in the spark plug hole.

The mower is a Snapper self-propelled with a Briggs & Stratton Quantum XM 5hp. Any ideas?

 

Hello bigbob1122,


Sounds like you may have missed properly cleaning the bowl retaining (main jet) nut, Here's a detailed guide; Disassembly, Cleaning and Repair of Briggs and Stratton / Walbro LMS Carb on Briggs Engine 125K02 0137


As for getting it started without putting fuel in the plug hole, These plastic air filter bases are known to warp over time. This reduces the sealing quality leaving the primer bulb non functional.

One fix is to replace this base with a new one or use 2 or 3 gaskets between it and the carb, I've added extra gaskets many times just to save the customer money and extra down time to order a new base in, Just don't over tighten the base screws.



Good Luck

 

I agree. The priming problem will likely be fixed once you clean the holes in the bowl nut.

 

Well, I tried cleaning the main jet but it still won't start. I had already tried cleaning the main jet but I went ahead and did it again just to be sure. I used carb cleaner and a paperclip to clean out the holes. I even checked it and gas is able to flow from the 2 lower holes and into the top(center) hole. It's about as clean as it's going to get.

Still, it won't start. Same symptoms. If I put a small amount of gas in the spark plug hole the mower will start for roughly 3-5 seconds and then immediately die and stop running. Also, gas has NO problem getting into the carb bowl.

Any other ideas, or do I just have a pile of scrap metal here?

 

Something is still clogged in the carb. You may have to take the whole thing off and clean it. There may be a small hole in the side of the post that the bowl nut screws into to hold the bowl on. Make sure that is clear as well, it this carb has it. Some just have a notch at the bottom.

 

Well, I already removed it once before and cleaned it about 2 weeks ago. Should I try it again?

 

Not just yet bigbob,


With the air filter removed, Shine a flashlight into the carb air inlet. You will see the emulsion tube sticking up into the carb throat, Push the primer bulb 2 or 3 times and see if fuel bubbles up out of this tube into the throat of the carb.

If your getting fuel into the throat when pushing the primer bulb and it still doesn't want to start up, You likely have low compression (not enough vacuum to pull fuel in) as a result of worn rings or non-seating valves. I've also seen worn exhaust valve guides cause this same symptom.....

 

Sometimes I have to clean a carb several times before the blockage finally comes out. Sometimes it's not apparent where the blockage is, but there is one somewhere. The only other thing I can think of is a problem with the intake to carb area, either the o-ring behind the carb missing or a broken or loose intake pipe.