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I mow for half an hour and the engine starts missing now and then and abruptly shuts down. the 21 hp Kubuto has 1300 hours new filters and the fuel line is clear so I can see no bubbles. I've checked for loose conectioons have got fresh fuel. Good temperature readings. When its running it is strong but quits and I wait a couple minutes and go back to cutting for 15 to 20 minutes, repeat. Could it be the fuel soleinoid?

if you don't have air leaks then the soleinoid would be my next item to troubleshoot....russ

173abn said:

if you don't have air leaks then the soleinoid would be my next item to troubleshoot....russ

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Thank you for the reply 173ABN. I'll check it. When I figure out what the problem is I'll post it.

5119andygsh said:

I mow for half an hour and the engine starts missing now and then and abruptly shuts down. the 21 hp Kubuto has 1300 hours new filters and the fuel line is clear so I can see no bubbles. I've checked for loose conectioons have got fresh fuel. Good temperature readings. When its running it is strong but quits and I wait a couple minutes and go back to cutting for 15 to 20 minutes, repeat. Could it be the fuel soleinoid?

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I have the same problem with my 722d that is a 2005 with 850 hours so it you find out what the problem is please let me know and I will do the same. Thanks , this is my email rollrite@msn.com

Are you sure that there is no fungus in the tank. There is a fungus that grows in diesel fuel and can cause strange problems. It shows up as grey, soft particles about the size of a BB. There is a product called "Biogard" that will kill it.

Hope this helps.

MBDiagMan said:

Are you sure that there is no fungus in the tank. There is a fungus that grows in diesel fuel and can cause strange problems. It shows up as grey, soft particles about the size of a BB. There is a product called "Biogard" that will kill it.

Hope this helps.

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I will try anything at this point, Thank you very much for the info.

My Kubota 25hp gas had a simular issue. It was the fuel shut off soleinoid. Not sure what the diesel one looks like, but on mine, its 2 small wire going into the bottom of the carb. The connections were corroded. If I turned the key on, (but not start mower), I wiggled the wire and could hear & feel it shutting off. I've seen diesel soleinoids on ebay for around $70.

5119andygsh said:

Thank you for the reply 173ABN. I'll check it. When I figure out what the problem is I'll post it.

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by passed seat safty switch and no more hiccups. ordering a new switch 13.00 bucks

It is not shutting down like when you get up off the seat, it is slowly powering down and then it return to normal high RPM's. Seems like it maybe getting air in the line but it doesn't do it all the time. I have changed all of the filters,

Check the fuel pick up tube . Remove the fuel line then unscrew the pickup tube and see if the tube is blocked with grass

Did you find the problem?? My 721d just started doing the same thing..will run perfect for an hour then it starts missing and if you look at the fuel return line it doesn't have a strong flow. If you shut the mower off and start again it will run fine for another 5 min. or so.....I'm going to take off the fuel pick up tube tonight to check if there is a blockage...side note, there is less then a 1/4 tank of fuel in the 9 gallon tank.