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120 john deere


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#1 Justin2655 OFFLINE  

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Posted July 12, 2015 - 03:28 PM

i have a john deere 120, ever since i got it has ran great, no problems at all, the other day i was driving it and while i was driving it started running like crap and back firing, tried adjusting the carb, that didnt work. pulled the carb apart and cleaned it, put a different coil on, different condensor, cleaned points, checked point gap, fuel line isnt plugged, and it still doesnt run right. put a different carb on it, that didnt make a difference either. it runs fine at an idle but when you throttle it up past idle, it back fires. just kinda weird that it all of a sudden just started running crappy.  what do you soppose it could be? has me stumped on this one :wallbanging:    thanks justin



#2 Trav1s OFFLINE  

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Posted July 12, 2015 - 04:45 PM

So beginning with the basics...  Does it still have the K301 in it?

 

New points/condensor/plug and known good coil tells me it is not an issue of spark.

 

Carb swap with known good carb tells me it is not fuel.

 

How about carbon or sticking exhaust valve.  I would pull the head, clean the carbon, lap the head, and reinstall with a new head gasket installed to the Kohler manual guidelines.



#3 lyall OFFLINE  

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Posted July 12, 2015 - 08:33 PM

Have you checked the throttle shaft for play.  If you can move the throttle shaft over .010 you are getting a vacuum leak.

It can be fixed, if you know how.



#4 farmerall OFFLINE  

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Posted July 12, 2015 - 08:40 PM

Maybe the head gasket blew.



#5 Justin2655 OFFLINE  

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Posted July 13, 2015 - 03:44 AM

I didn't think about the throttle shaft, I'll have to check that out. Pulled the head off and everything was fine there, head gasket was fine. Gonna throw it back together and check the throttle shaft. Hope I can get it figured out one way or another lol. Thanks justin






Have you checked the throttle shaft for play. If you can move the throttle shaft over .010 you are getting a vacuum leak.
It can be fixed, if you know how.


Edited by Justin2655, July 13, 2015 - 03:45 AM.


#6 Justin2655 OFFLINE  

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Posted July 13, 2015 - 06:36 PM


I pulled the head off and nothing looks abnormal. I don't get it



So beginning with the basics...  Does it still have the K301 in it?
 
New points/condensor/plug and known good coil tells me it is not an issue of spark.
 
Carb swap with known good carb tells me it is not fuel.
 
How about carbon or sticking exhaust valve.  I would pull the head, clean the carbon, lap the head, and reinstall with a new head gasket installed to the Kohler manual guidelines.






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