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Kevin, Technician
Category: Small Engine
Satisfied Customers: 732
Experience:  Over 10 years as a Deere Service Tech.
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I have a John Deere Z425 with a Briggs 23hp OHV V-twin... Starts

Resolved Question:

I have a John Deere Z425 with a Briggs 23hp OHV V-twin... Starts w/choke on and dies after a few seconds. Won't start w/choke off. Replaced: fuel filter, fuel pump, fuel line, fuel solenoid, spark plugs, cleaned and rebuilt carb & air cleaner, replaced head gasket. Has good spark, gas getting to carb through clear fuel lines, but acts like it starves for gas. Any ideas?
Submitted: 7 years ago.
Category: Small Engine
Expert:  Kevin replied 7 years ago.

Hello, my name is XXXXX XXXXX I can help you with your question.


Deere found that some Z425 mowers below serial number 060579 have had a common carburetor problem. It seems that the carburetor float needle sticks in the closed position and causes to the engine to starve for fuel. If your mower is below this serial number then there is a new needle valve available from your local Deere dealer that will resolve this issue. The new needle is part number LG690985


If this has helped to resolve your issue, please hit the green "Accept" button so I get paid for helping you. If you need further assistance please reply to this message and I will do my best to help you out.




Customer: replied 7 years ago.
Yeah, I read about that. My first approach was to clean and rebuild the carb, thinking it was gummed up. I did that and noticed the new needle in the rebuild kit was metal, as opposed to the plastic one that came with it new. After I put it back together, I was still having the same problem, so took just the float bowl off to see if the float and or needle jet was sticking, but it isn't. It toggles up and down freely.
Expert:  Kevin replied 7 years ago.

While the carb is still the most likely cause of the problem I'm glad to hear that you have already changed the needle. If your engine runs with the choke on but not with it off then it would indicate that the carb bowl is still not staying full or the main jet is plugged. If you disassemble carb and hold the top half with the float upside down the carb float should sit parallel to the carb mating surface. If your float does not sit level then there may be a problem with the float itself. Old floats were copper or brass and could be adjusted but the newer ones can only be replaced when they wear or deform.


As far as the main jets the newer carbs are very difficult to clean properly. I like to use torch tip cleaners (which consist of a series of different size ribbed wires) to push through the jets in the car. some of the passages are not straight which makes them very difficult to clean. You could also get some carb cleaning dip to soak the carb in for 24 hours. The cleaning dips will dissolve many of the varnish deposits that occur naturally when the engine sits.


Let me know how you make out.




Edited by Kevin on 7/11/2010 at 9:27 PM EST
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