I just bought a used riding lawn mower. It had started fine each time I went to look at it. Looks like it was been treated well although quite dusty. I was told that it was used very little in the last few years. It is a MTD 16.5hp riding mower.

So I brought it home today and mowed the front yard with it. It backfired twice when being shutdown. From what I have read that is because it was not sufficiently idled down. Now I cannot even get it to start. I have removed the air filter to get a better look at the carb. When I tried to start it and had the carb exposed, it would have some gas coming from the carb, but would not start.

I have not tried any real troubleshooting yet. I wanted to get a few leads as to where I should start.

I am not particularly mechanically inclined, so any help is sincerely appreciated!

Thanks,
Miah

Have you used the choke? If not, pull the choke so the butterfly valve in the throat of the carb restricts the air intake. If this works, ease off on the choke once it has started. I have noticed when I am running my rider with the choke in the wide open position, the engine will sometimes backfire when I shut it off.

Hope that helps,
Rick

Rick,

Do you mean use the choke to start it or to alleviate the backfire when powering down. My biggest concern right now is getting it to start. Do you think the plug might be bad? I plan to replace it tomorrow and to see what happens.

Thanks I appreciate the help.

What brand engine, is it a over head valve engine or side valve (flathead)?

I meant when you start up. Certainly, the plug is a good place to check if the choke doesn't work for you.
Good luck!

Had this happen to my MTD.. it`s something worth looking at... mine is a 14.5 hp Briggs engine.I hit a bump and the engine died.. wouldn`t restart yet there was plenty of gas getting to the carb.there is a wire going to the bottom of the carb... its a shut off.. works like a needle and seat on a automobile carb but in reverse.. it shuts the flow of gas off... that wire has to be live when the key is turned to on.. mine lost contact when I hit that bump.. but it looked connected.well anyway I made a mess of fixing it so I just jammed the plunger in the open position and finished the lawn... be careful when working on it though cause nothings holding back the flow of gas while you`re fixing replacing the part... the plunger unscrews from the carb... hope this helped..

First, see if you have spark. Disconnect the spark plug wire, pull the starter, and see if you have a solid spark, when you hold the plug wire about 1/4" from from the tip of the plug or a cylinder head bolt. If you have a solid spark, then you know the problem is with the fuel system; e.g. gasoline, carburetor, fuel line, or fuel pump.

This site should help you with lawn mower repair and care. It's got a few general trouple shooting lists you an try.

Have you checked the flywheel key?

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Originally Posted by miah

I just bought a used riding lawn mower. It had started fine each time I went to look at it. Looks like it was been treated well although quite dusty. I was told that it was used very little in the last few years. It is a MTD 16.5hp riding mower.

So I brought it home today and mowed the front yard with it. It backfired twice when being shutdown. From what I have read that is because it was not sufficiently idled down. Now I cannot even get it to start. I have removed the air filter to get a better look at the carb. When I tried to start it and had the carb exposed, it would have some gas coming from the carb, but would not start.

I have not tried any real troubleshooting yet. I wanted to get a few leads as to where I should start.

I am not particularly mechanically inclined, so any help is sincerely appreciated!

Thanks,
Miah

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I'd suspect your shear pin or woodruff key to start with. A serious backfire can damage the key just enough to take it out of time. It's not a big deal to change. Pull the flywheel and check for any marks on the key. If there are marks, it probably moved enough to cause problems or will shortly.

Thanks for the tip about the valve on the bottom of the carb. My mower also had gas getting to the carb, and had a spark, but would not start. I never smelled gas when I was cranking it so it made sense. I removed the valve, cleaned around it and retried, still no luck. Then I jammed the needle open with a piece of wood so I could mow the lawn. That worked fine. Now I have to determine if the valve is bad or is it the wiring.