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JD420S starting/running difficulties

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Henry

12-12-1999 06:27:55




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Bought 420 that hadn't run for a couple years. Cleaned carb and fuel filter/bowl asm, drained and refilled tank, new plugs & wires, points/cond look OK. Can only get it to fire by using ether, and to run when at nearly full choke. Obviously lean mixture, suspect vacuum leak, but haven't checked for that carefully, yet. Haven't checked compression or timing yet, either. Supposedly the tractor ran OK when last used. Wondered if these old 2 cyl tractors are just naturally hard to start when the temperature gets below 40 or 50 degrees? Comments & advice appreciated.

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Ken Talatzko

12-12-1999 20:06:49




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 Re: JD420S starting/running difficulties in reply to Henry, 12-12-1999 06:27:55  
It sounds like you've got a fuel problem. Either gas isn't getting to the carb,or you didn't clean the carb well enough. Disconnect the fuel line at the carb and see how much gas runs out. It should be a steady stream. If it isn't the problem is in the sediment bowl or the bottom of the tank.If you've got good flow.the problem is in the carb. I believe the adjustment at the bottom of the carb is the load adjustment and it is suposed to look bent. The brass screw at the top of the carb is the idle mixture adjustment. Also I've had the fuel line completely plugged.

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Paul

12-12-1999 07:47:47




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 Re: JD420S starting/running difficulties in reply to Henry, 12-12-1999 06:27:55  
I'm not much of a mechanic, but I'd try a new condenser. The old 2 cylinder tractors are not naturally hard to start.



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lc

12-12-1999 11:40:17




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 Re: Re: JD420S starting/running difficulties in reply to Paul, 12-12-1999 07:47:47  
Have a 40 which is similar to the 420. One of the easiest tractors to start. Do always choke it. I wonder if your fuel adjustment screw at bottom of carb needs to be set richer, assuming the spark is ok.



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Tugboat

12-14-1999 14:08:43




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 Re: Re: Re: JD420S starting/running difficulties in reply to lc, 12-12-1999 11:40:17  
The screw at the top is your idle mixture but it sounds like it's running so bad that it never gets down to an idle. You may want to set this screw at about 1.5 turns out as a starting point for further adjustment after you find your main problem. Sounds like fuel starvation but a leaking manifold can cause a similar condition. When everything is right, these engines start great all the time. Especially on 12 volt. Find your problen and throw that ether away! Tugboat

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1c

12-12-1999 19:14:35




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 Re: Re: Re: JD420S starting/running difficulties in reply to lc, 12-12-1999 11:40:17  
Am going to try a condenser as suggested by Paul. Glad to have you both indicate starting isn't usually diffficult. The head of the adjusting screw at the bottom of the carb is damaged (bent over). I'll see what I can do. May need a kit. What is the slotted brass screw at the top of the carb for? I've messed with it a little but nothing seemed to change. Thanks for the help. Henry

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Sam

12-15-1999 21:00:18




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 Re: Re: Re: Re: JD420S starting/running difficulties in reply to 1c, 12-12-1999 19:14:35  
We have a 430S - very same engine that starts and runs the best with the origonal 6 volt system.



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