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JD 730 Gas Misfiring Badly

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DG

08-09-2002 13:25:27




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Any ideas on what to try with a JD730 (gas) misfiring terribly. New dist. cap, plugs, wires, coil, etc. & timing checked out ok. Junkyard carb. installed recently, suspect a fuel problem. Any suggestions appreciated.




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gwh

08-09-2002 20:01:59




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 Re: JD 730 Gas Misfiring Badly in reply to DG, 08-09-2002 13:25:27  
DG, Clooney indicated a tight valve as a possible problem, for what is takes to check the valves i would pull the valve cover and do it. Leave the feeler gauges in your tool box and with each valve closed adj. the adjustment screw to zero lash and back off just 2 flats of the screw this will give you a hair over .020 operating clearance. Don't worry about the engine being hot just do it cool(cold), this may not be a perfect adjustment and the valves may be a little noisy but will elimiate a tight valve as a misfire concern.

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Jack

08-09-2002 13:31:34




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 Re: JD 730 Gas Misfiring Badly in reply to DG, 08-09-2002 13:25:27  
Is it doing it under a load,at high idle,or just idling?How does your points look?Have you had the carb apart yet?Just need a little more info.Jack



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DG

08-09-2002 13:36:12




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 Re: Re: JD 730 Gas Misfiring Badly in reply to Jack, 08-09-2002 13:31:34  
Starts fine. Begins missing after warmup, at idle with no load & same at full-throttle with load. Points also are new. Haven't touched the carb yet, that's next to try, although it was running same way with the old carb before junkyard carb instralled. Cleaned sediment screen, its ok.



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Clooney

08-09-2002 15:18:41




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 Re: Re: Re: JD 730 Gas Misfiring Badly in reply to DG, 08-09-2002 13:36:12  
DG, run a [hot] compression test to see if you have a low compression cylinder or tight valve.
~Check the coil [ign switch side] to see if the ignition resistor is there & working [should be 6-8 volts] if 12 volts or over, the resistor is missing.
~Does running with the choke on help? If so suspect carb problem or intake/intake gasket leak.
~Make sure the heat valve is turned to EXACTLY hot or cold & not in between.

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Jack

08-09-2002 13:42:07




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 Re: Re: Re: JD 730 Gas Misfiring Badly in reply to DG, 08-09-2002 13:36:12  
Make sure you are not running Champion plugs.I have seen the coil act up after warm up and cause simular problems.Have you got another coil to try on it?



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DG

08-09-2002 13:54:41




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 Re: Re: Re: Re: JD 730 Gas Misfiring Badly in reply to Jack, 08-09-2002 13:42:07  
I'll show my ignorance here, but why not Champion plugs?



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Clooney

08-09-2002 15:04:05




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 Re: Re: Re: Re: Re: JD 730 Gas Misfiring Badly in reply to DG, 08-09-2002 13:54:41  
DG, that's a good question. While a lot of people seem to have a problem with Champion plugs I run Champions in many of my 2-cylinder tractors & don't seem to have any problem with them. [I run the plug gap at .040" though & maybe that makes a difference].
~I've heard [the reason given for the problem with Champions] is everything from the plating on the Champion metal to the porosity of the center porcelain to the length of the center electrode but haven't been able to prove or disprove any of it.....

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Jack

08-09-2002 14:17:09




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 Re: Re: Re: Re: Re: JD 730 Gas Misfiring Badly in reply to DG, 08-09-2002 13:54:41  
These old Deeres don't like Champion for some reason.I had an A with a brand new set in it and just went to sputtering and cutting up and after going through the carb and cleaning the tank and replacing the points I said what the heck and throwed in an old set of plugs I had(prestolite) and smooth as silk.Seen it a bunch,and I have heard why they don't work well in twobangers but it's been so long ago I would be afraid to go into that.There was a 50 JD at a pull one day and he was cutting up badly and after checking everything somebody asked what kind of plugs he was running and of course,Champion.He ran to the parts store and came back with Autolite 386's and installed them.It was like a whole different machine,ran perfect.

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