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JD B Compression ?

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EW

11-26-1999 13:56:03




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I have a 47 B that there seems to be a certain amount of crankcase gasses coming out around the belt pulley. Is there a breather that may be plugged? Or is there a bad seal in the belt pulley? I also concidered that maybe it was excesive blow-by from the rings,so I checked the compression and both cylinders were 65#/sq in. I thought that was a little low comparing it to automotive engines. What should the compression be? THANKS For Any Help.

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Terry Welshans

11-29-1999 19:11:12




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 Re: JD B Compression ? in reply to EW, 11-26-1999 13:56:03  
EW, there is a crankcase breather air pump on the fan shaft, right at the back, on the governor box. It is connected by a long tube up to the intake pipe ahead of the carburetor. If the air pump is not pumping, it won't pump the smog out of the crankcase and pressure builds up and oil blows out of the seals and gaskets.

Take the pipe off the pump and start it up. There should be a brisk flow of air out of the pump. If there is no flow, the pump may need rebuilding (a lot cheaper than engine rings and a valve job)

Terry Welshans

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Ron D

11-26-1999 18:14:08




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 Re: JD B Compression ? in reply to EW, 11-26-1999 13:56:03  
The early tractors should have aprox. 70 psi give or take five, later tractors such as a 47 on up should have a 100 psi again give or take five pounds. As john was saying engine should be at running temperature and be sure throttle is in the wide open position when making the test , it needs all the air it can get. Ron D



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EW

11-26-1999 18:50:18




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 Re: Re: JD B Compression ? in reply to Ron D, 11-26-1999 18:14:08  
Thanks for all the comments. The test was done with engine cold, no throttle. I will try again as you have described. The tractor really starts very good, but the harder it is worked, the more blow-by comes out. It can be barely noticed at idle,but work it on a chopper, it really comes out like steam.This is my first 2 cylinder JD, so I dont know much about them. I was thinking about finding a 3-point conversion for it. As I see it now, it looks like a overhaul kit too.

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Nathan(GA)

11-26-1999 19:26:13




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 Re: Re: Re: JD B Compression ? in reply to EW, 11-26-1999 18:50:18  
EW, I wouldn't jump to overhaul just yet. Recheck compression as described. Unless that blowby really bothers you, I wouldn't touch it. I have seen old tractors work many years with the blowby. As long as it cranks and runs good, keep on chopping.
Good Luck, Nathan



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EW

11-27-1999 17:42:19




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 Re: Re: Re: Re: JD B Compression ? in reply to Nathan(GA), 11-26-1999 19:26:13  
I retested the commpression and came up with 85# on both sides. I had it on the log spitter today and I noticed one cylinder was not firing right, but as soon as put a little load on it, it would striaghten out. When I pulled the plugs for the comp test the one on the right side was somewhat wet, not soaked, but wet. So, something is not right. I can pull the wire from the plug on the right side while running, and there is little to no change in sound or rpm. Do the same on opposite side almost kills it and sounds weaker. I have ruled out the plugs. Looks like tear-down time, would you agree?

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Nathan(GA)

11-28-1999 11:33:17




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 Re: Re: Re: Re: Re: JD B Compression ? in reply to EW, 11-27-1999 17:42:19  
Well, not yet. I don't know which plug you're running, but from what you said, sounds like a plug or plug wire. If you are running Champions, throw them away, according to everybody on here. Get some Autolite 386 or 388 or AC C88L. I ordered the 388, but haven't put them in yet. Try this and swap the wires and see if any different. Your compression doesn't sound that bad. You may have to rebuild, but I like to save money when possible. Let me know what happens.
Good Luck, Nathan

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EW

11-28-1999 15:37:10




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 Re: Re: Re: Re: Re: Re: JD B Compression ? in reply to Nathan(GA), 11-28-1999 11:33:17  
Thanks for the reply.
It has new points,cap, wires and was using d 21, or d23 champions. I switched plugs and sides and it is consistantly weak on right side. It would be cheaper to try a different brand plug than overhaul, especially since both cylinders have exactly the same commpression, witch rules out extreme wear on one cylinder.



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John T

11-26-1999 15:21:24




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 Re: JD B Compression ? in reply to EW, 11-26-1999 13:56:03  
EW, behind the pulley assembly there are some drain holes so oil in that aree will drain back down as opposed to slinging out on the exterior, which may need cleaning. The compression is a little low if thats a wet test after oil has helped seal the rings and still low, but not quite as bad, if its a dry initial slow turn over test. If you're getting a lot of crankcase pressure (blow by) and smoke out the crankcase, thats excess blow by past the rings which, along with a low compression reading, probably means the rings are getting worn. Low compression can also be caused by leaky valves you know, even if the rings are perfect. John Nordhoff aka Ol John T in Indiana

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Chuck

11-26-1999 14:50:03




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 Re: JD B Compression ? in reply to EW, 11-26-1999 13:56:03  
got some bad news, your compression is gone...you should have about 100PSI minimum



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MARK

11-28-1999 08:32:33




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 Re: Re: JD B Compression ? in reply to Chuck , 11-26-1999 14:50:03  
TIME FOR SOME NEW RINGS.



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