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Bad idle on 40

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Mark Wengert

07-15-2001 18:39:12




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I have a Jd 40 and since I have had it I have not been able to get it to idle smooth. I rebuilt the carb with a JD kit and it improved a little. I have new rings in it, 110 psi compression on both cylinders. The gap is correct on the distributer and tappets. Govenour has no broken weights or any signs of wear inside. So where do I go next? Valve not seating good some times? It reves up the longer you run it and soon just doesn't idle at all. Back fires a little through intake. Any suggestions would really be great. I am lost now. Runs good on high idle and load. Think about it and please give any ideas. Thanks for the help.
Mark

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CPeter

07-17-2001 08:24:47




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 Re: bad idle on 40 in reply to Mark Wengert, 07-15-2001 18:39:12  
Did you replace the throttle shaft, bushings, and seals when you did the rebuild on the carb? The first one I did, I wondered what all these parts were for until I took the carb apart and saw how much wear there was on the shaft and bushings. They wear because they are in a dusty environment and because the governer has them in motion all the time. You can get quite a vacuum leak at this location which will cause exactly the symptoms you describe. I got my kits from Central Tractor.

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MN Bob

07-16-2001 19:33:30




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 Re: bad idle on 40 in reply to Mark Wengert, 07-15-2001 18:39:12  
Mark; Do you have the service manual? I bought one and I see it has the normal carb adj procedures, then how to adjust for black smoke and backfire when clutch is released, Then says if it cannot be satisfacorly adjusted, refer to carb cleaning and overhaul. If copies of these pages could help I could scan them for you. Bob



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Prune Picker

07-16-2001 11:58:13




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 Re: bad idle on 40 in reply to Mark Wengert, 07-15-2001 18:39:12  
Mark, make sure you have the throttle linkage set correctly. It's simple to do. Then I would suspect either a vacuum leak on the carb, or a passage that wasn't clean when you rebuilt it. The carbs need to be thoroughly cleaned...all air and fuel passageways. Does the condition change by screwing in the idle jet? Lastly, check your intake manifold for cracks or a bad gasket.



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L.C.

07-15-2001 19:56:53




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 Re: bad idle on 40 in reply to Mark Wengert, 07-15-2001 18:39:12  
I would suggest checking the timing because of the backfire, but that may not solve all of your problems. I'm a little suspicious of the carb, but I'm no expert there.



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