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620 running problem

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John VB

11-03-2002 20:41:05




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My 620 was running great this morning. It had been leaking fuel into the crankcase. Thanks to a tip here, I replaced the diaphrams in the fuel shutoff assembly. They were shot. I also replaced the o-ring on the fuel metering needle in the carb as it was leaking there. Now I have no leaks, but the tractor runs poorly. It lacks power and has kind of a tinny sound where before it had a nice deep good sounding pop. It also resists accelerating when the throttle is advanced. My guess is that it is not getting enough fuel. I set the fuel metering needle at 2-1/4 turns out and went both in and out a full turn and it made no difference. There is a bubble at the top of the sediment bowl that doesn't seem to want to go away, but that may be normal. The bowl filled fine by pushing the primer down. I didn't really do anything that should affect the way it runs, except maybe broke some gunk loose and it is now causing problems. Any suggestions would be appreciate. Thanks.

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John VB

11-05-2002 06:38:04




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 Re: 620 running problem in reply to John VB, 11-03-2002 20:41:05  
Close but no cigar. Read my previous post about the plug wire problem. Anyway, I installed new plug wires and guess what, same problem. Left cylinder still not firing. To verify, I pulled the left plug wire off the plug. The cyclinder wasn't firing, but something sounded different as I pulled the wire off the plug. Turns out that the tractor runs fine when I hang the rubber boot of the plug wire on the end of the plug, but the cylinder won't fire when I actually connect the wire to the plug properly. I have never seen anything like it. I am hoping it is a bad plug and will replace both of them today. Hope I have good news to post.

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Clooney

11-05-2002 06:42:36




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 Re: Re: 620 running problem in reply to John VB, 11-05-2002 06:38:04  
John, when it fires with the wire just close to the plug it is usually a sign of a partially fouled sparkplug.



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John VB

11-05-2002 12:02:56




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 Re: Re: Re: 620 running problem in reply to Clooney, 11-05-2002 06:42:36  
Thanks again Clooney. I put a new set of plugs in and the 620 runs great again. Man I learned a lot with this little episode. Guess that is what makes it fun!



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Clooney

11-04-2002 03:42:34




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 Re: 620 running problem in reply to John VB, 11-03-2002 20:41:05  
John, you could have a carb problem or maybe you fouled a spark plug with all the diluted oil that was in it.
~Start with a fresh set of spark plugs then if it still acts up move on to the fuel system.
~Open the carb drain plug on the bottom of the carb, then hold the knurled knob in on the strainer assemble & MAKE SURE you have a small pencil sized stream of fuel for AT LEAST 30 seconds, if not, you have a restriction in the fuel system. Don't stop too early & let a bowl of fuel fool you.
~If a restriction is noted, start with the carb inlet screen just above where the fuel line enters the carb.
~Can you visually see the strainer valve open with the engine running ? If not make sure the diaphragms are in correctly.
~You won't get much action out of the load screw as that is more of a fine tuner instead of a true load screw on the dual DLTX carbs. The actual load jets are built into the carb..

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John VB

11-04-2002 11:52:47




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 Re: Re: 620 running problem in reply to Clooney, 11-04-2002 03:42:34  
I THINK I have found the problem. When Clooney mentioned spark plugs, I pulled them to have a look since I couldn't think of anything else to do. One plug was soaked with fuel and one was dry. So I started the engine and pulled the plug wire on the dry plug and the tractor stopped. I then pulled the plug wire on the wet plug and it ran like it had been running. It was only running on one cylinder. I then pulled the distributor end of the plug that wasn't firing and the connector wasn't even in the socket and it was baddly charred. I have a new set of wires to put in and am sure it will run fine then.

Question: Why did this problem show up the exact same time that I had replaced the fuel shutoff diaphrams? Coincidence? I wonder. I will let you know later today if the problem is solved.

Thanks again.

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John VB

11-04-2002 06:11:35




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 Re: Re: 620 running problem in reply to Clooney, 11-04-2002 03:42:34  
Thanks for the reply Clooney. The strainer valve opens about 1/4-3/8 of an inch with the engine running. Easy to see with the nice clean glass bowl. The drain plug on my carb bowl is not removable. Previous owner completely rouned it off and it is well corroded in place. I will loosen the fuel line where it enters the carb and check for fuel flow. At least I will know it is ok to there. I will also check the carb inlet screen. I found out about that late last night while reading the manual. Thanks again.

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G Taylor

11-04-2002 07:32:31




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 Re: Re: Re: 620 running problem in reply to John VB, 11-04-2002 06:11:35  
As Clooney pointed out to us one time the seal between carb fuel bowl and carb body is vital. Any corrosion and stress trying to loosen parts may have broken the seal. It would tend to make the engine run rich at light loads however. Fortunately Mother Deere still has the bowl & gasket in stock for a modest fee. The carb's gas screen can corrode with time letting dirt through into the carb.

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