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620 compression

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jack

10-09-2000 08:26:57




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My brother just purchased a JD 620 gas. The tractor needs carb and distributer work to be in running condition. While going over the tractor trying to decide what all else she needed we found that the compression readings were 90 in one cylinder and 70 in the other. These readings were on a cold engine as it is not yet running. My question is are these compression readings acceptable or a sign of a worn engine in need of a rebuild. Any help will be appreciated.

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burnsOmatic

10-09-2000 16:31:55




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 Re: 620 compression in reply to jack, 10-09-2000 08:26:57  
Jack, I found that my 48 A varied only 8-10 psi between a cold engine and engine brought up to operating temp



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Bill {Antique Acres}

10-09-2000 08:41:45




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 Re: 620 compression in reply to jack, 10-09-2000 08:26:57  
You really need a hot reading to be accurate. But if you go with those, the one is getting pretty low. A fresh engine should run 110 - 120. 90 will get you by for a while, but 70 isn't to strong. It could be if it hasn't run in a while the rings are somewhat unseated and the valves are not closing tight. I would check it again after you get it running and go from there. Bill {Antique Acres}



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Chuck

10-09-2000 10:31:41




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 Re: Re: 620 compression in reply to Bill {Antique Acres}, 10-09-2000 08:41:45  
I agree with Bill, also if you go into the engine and put rings, be sure you have valves checked.



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G Taylor guides too

10-10-2000 08:36:43




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 Re: Re: Re: 620 compression in reply to Chuck, 10-09-2000 10:31:41  
New valve guides are cheap insurance too. New or newly ground seats and valves will rapidly fail when the valve doesn't hit the seat squarely. Try the compression with a squirt of oil in each cylinder to check for a difference. I assume you are electricaly cranking the engine with both sparkplugs out and the throttle wide open? We figured out only ancient Champions without the "U" in the number work in Deere's. Go with new non resistor Autolites, AC or something and solid core wires. If ordering pistons go with propane (LP). The new gasoline has enough octane to use them. power and fuel efficiency will be improved. The aircleaner will be full of oily mud. You must at least remove the inner mesh and steam clean.A better cure is a cheap upgrade to a paper element from Renaissance Tractor. 1-360-748-0026.

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