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My john deere 345 mower is running rough ,popping, no power, backfiring, using over halve the gas it should, with some black smoke. can mow halve may yard, take a brake and it will start right up, but will not stay running. have replaced the plugs, shot off fuel solenoid, fuel filter, and the carb and air filter are clean. never posted in a forum before, so thank you in advance.

Sounds very much like the main jet has fallen out / come loose
Or a valve seat has come loose

How many hours on the 345?

395 hrs

Have a 1996 345 with about 650 hours.

Similar problem; It will run for about 10 minutes then quit. It will restart but will only run for a minute or so. I have done the easy stuff; cleaned carb a couple times, changed fuel filter, plugs, air filter.
It ran well for years; even though not many hours. Has anybody found that non-ethanol gas is better?

I'm also curious if coolant is not circulating; thus engine is overheating. It's very frustrating as I really need it to work right now since grass is growing so fast.

Any insight greatly appreciated.

Did you check to see if it is only running on one cylinder? Pull one spark plug wire and see if it starts. Reinstall and repeat on the other plug. If the unit starts with only one wire attached, the other cylinder is not firing.

So still having the same issue as in it dies after 20 minutes or so. The oil is not low but old; probably could use a change. Could old oil cause it to die after a running a while? Doesn't seem so to me but any insight would be great.
thanks,

Westhp said:

So still having the same issue as in it dies after 20 minutes or so. The oil is not low but old; probably could use a change. Could old oil cause it to die after a running a while? Doesn't seem so to me but any insight would be great.
thanks,

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No.

I have found that the Non-Ethanol gas keeps longer with less issues. My old mower took me 4 1/2 hrs to mow my yard and a full tank of gas so I used Ethanol gas because of price but at the end of the year my last few tanks were the Non-Ethanol because it was going to be setting up over the winter. I have found that the alcohol in the Ethanol gas attracts water and that causes problems down the road.
As far as your problem, I have a JD 757 with a Kaw engine and through much research I found out they were subject to over heating. Mine did the same thing, would run for maybe an hour or two and then it was like you had shut off the fuel and would only run with the choke pulled out if at all. Let it sit for a little bit and it would start up and run for a little while then the same thing would happen. I ended up pulling the carb and figured out that the bowl had actually warped just enough that the float would hang almost closed on the side. I took a flat file and removed about .003 to .004 of material from the side and it has been running like a champ since.

thanks for the info; that makes sense. I definitely plan on using non-ethanol gas moving forward. You talking about the carb really makes me think it has to do with that. It's ran fine, well a little rough, all these years, never died like it does now. I'll take the carb off again and check the float.

talking to a colleague... he mentioned the fuel hoses could be breaking down and contaminating the carb; he's that that happen. I may replace those too.

Westhp said:

thanks for the info; that makes sense. I definitely plan on using non-ethanol gas moving forward. You talking about the carb really makes me think it has to do with that. It's ran fine, well a little rough, all these years, never died like it does now. I'll take the carb off again and check the float.

Click to expand...

Just look at the side of the bowl and the float to see if there is or has been any rubbing