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51B Teardown Confusion

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greg

12-18-1999 17:35:44




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I am tearing down the engine investigating an acceleration knock. You know the engineer type with his first old tractor... Anyway, I have the manual and parts book and have been reading this board for a year. I am ready to pull the pistons and the manual says to set the rod bearing clearances now because the new rings change the feel. I guess I could but this is new to me. In looking at the top of the pistons I see a couple of conical shaped clearances and one piston has a chip missing (.12 x .38") in this region such that I can see a section of the top ring. I am familiar with plastigage and automotive engines but not babbit (sp?) bearings. Do I go ahead and set the rod adjustment now? I did notice location punch marks on the rods indicating someone has been here before. I guess tommorrow I will see the journal condition. The rest of the tractor is in generally good condition. Also , when I go back together will I have any problems obtaining new gaskets? I have taken the radiator apart as well. Thanks guys. Later, Greg

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Greg

12-19-1999 10:36:28




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 Re: 51B Teardown Confusion in reply to greg, 12-18-1999 17:35:44  

Well, I am now further into the 51B. I have a piston and rod out and it has automotive style rod bearings and no shims. The parts manual seems to acknowledge this (rod B3201R) but the service manual only refers to spun babbitt. One of the rod bearings is into the brass. A preliminary journal check (with calipers, I'm going to have to borrow larger mikes, etc.) doesn't look that bad yet. The top ring groove side clearance is .028". That sounds bad. I do feel some amount of ridge on the cylinder wall. (Rob, you were right on time with the engineer-fits remark, you certainly understand them!) So based on what we see now- Should I pull the crank? How do I deal with these automotive style appearing rod bearings as far as establishing clearances? Also, I see no indication of replaceable push rod tubes like the manual talks about. By the way, the size of some of these parts amaze me. Thanks everybody, This is getting fun! Later, Greg

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Village Blacksmith

12-19-1999 13:40:08




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 Re: Re: 51B Teardown Confusion in reply to Greg, 12-19-1999 10:36:28  
The guys have good ideas, but seem to have missed one of your important points. You do not have babbitt bearings!!! You have automotive type replaceable bearings. You should handle their replacement just as you would bearings in your automotove engine. Check the size, then order undersized bearings if necessary, or you may be able to use standard size. Your JD Dealer should have these availabe. If not, go to a good bearing supply company. No shims are used and none can be used with this type of bearing. Believe me, you have got lucky on this one. Re-babbiting rod bearings can get very expensive, compared to a few bucks for replaceable bearings. Your main bearings could possibly be the same, but not necessarily. Ain't it FUN!!!

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BIG SWEDE

12-20-1999 08:37:50




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 Re: Re: Re: 51B Teardown Confusion in reply to Village Blacksmith, 12-19-1999 13:40:08  
Village Blacksmith sure is right I got right into answer because my '51 B has babbit style bearings.Need to pay closer attention I guess.



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Greg

12-19-1999 16:59:37




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 Re: Re: Re: 51B Teardown Confusion in reply to Village Blacksmith, 12-19-1999 13:40:08  

Thanks for the input VB. I am enjoying my 'lucky' feeling. I think the others missed my question because I unintentially misled them. I am new to this and by reading the manual, it doesn't discuss replaceable bearings. I assumed I would find shimmed babbitt and hence I asked how to do it before I took it apart (sorry Guys-still good info though). Something else... the rod cap nuts have thin castellated type slots in them (not for cotter pin) like I have seen before on prevailing torque locknuts but I can finger spin them on. My gut feeling is these nuts should be tight to turn. I sure appreciate the help. Later, Greg

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Rob

12-18-1999 18:11:00




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 Re: 51B Teardown Confusion in reply to greg, 12-18-1999 17:35:44  
Greg, being an engineer, what I'm going to tell you now will probably give you fits. I have found that the rod journals on these tractors almost always wear out of round, or egg shaped. This makes it really hard to use plastigauge or measure to find the journal size. An old JD mechanic told me how to set the bearing clearance this way; Take one or two thin shims out of each side of the rod (keep the thick shims on the outside of the stack and take equal amounts from each side of the rod), then replace the caps and torque to spec. If the crank still turns easily all the way around, remove another thin shim from each side of the rod , tighten to spec and turn it over again. When you find a tight spot and/or can't turn it over, replace one of the shims in each side. The shims are approx .004" and this will give you sufficient clearance to run the motor without binding the bearings. This method works for the mains also. The reason for doing it at teardown is the new rings will make it harder to turn the crank after assembly. I know it's not perfect, but unless you are farming a hundred acres with this tractor, it will last you the life of the overhaul.
Hope this helps even if it is a bit long.
Rob

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Wind

12-20-1999 13:46:08




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 Re: Re: 51B Teardown Confusion in reply to Rob, 12-18-1999 18:11:00  
Another question Rob. On a 1935 B, S/N 5964, what do you recommend as far as rod bearing replacement? The block will have to be pulled for a clean out bore of the cylinders as one had been stuck at one time and is quite pitted. Should the rod bearings be replaced even if they seem pretty tight right now. Also, do you know of any place to get the overhaul kit for that early of Deere? All I have been able to see in catalogs at this time are post 200,000 s/n. Thanks for the info.

Wind

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Rob

12-20-1999 18:12:37




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 Re: Re: Re: 51B Teardown Confusion in reply to Wind, 12-20-1999 13:46:08  
If the babbit [babitt?] looks smooth and in good shape, and if the rods look good, there should be no reason to do anything more than clean everything up and reassemble. You say they are tight, so all you have to do is mark which side they came off of and make SURE that the shims from each rod are kept in their original locations. There is a recommended method for shaping newly poured bearings to the crank that involves shaving the bearing, but hopefully you'll never have to learn it.
I'll check my sources for parts for the older stuff and post it if I find some. Anybody else know of a good supplier?

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Greg

12-19-1999 17:42:55




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 Re: Re: 51B Teardown Confusion in reply to Rob, 12-18-1999 18:11:00  

I appreciate your detailed response. I was all ready to follow it to the letter and then discovered the replaceable bearings! Keep an eye out for me in future posts - I'll need the help. Thanks, Greg



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BIG SWEDE

12-19-1999 07:29:59




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 Re: Re: 51B Teardown Confusion in reply to Rob, 12-18-1999 18:11:00  
Rob is telling it just like a man who is still repairing two cylinder tractors today and has been ever since he was a boy. His dad owned a JD dealership and he continues to run it as a repair shop to this day and is in his late sixties or early seventies. He gets my nod when it comes to experience.



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mark

12-19-1999 08:36:12




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 Re: Re: Re: 51B Teardown Confusion in reply to BIG SWEDE, 12-19-1999 07:29:59  
when removing shims it's not necessary to remove from both rod bolts. you can remove one shim if necessary....



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BIG SWEDE

12-19-1999 13:29:54




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 Re: Re: Re: Re: 51B Teardown Confusion in reply to mark, 12-19-1999 08:36:12  
Never tried one side at a time. Seems like keeping them even would be a good idea.Also I suppose it goes without saying that if the babbit doesn't stand up to careful inspection it's back to square one once that is repaired.



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Dan

12-18-1999 17:47:56




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 Re: 51B Teardown Confusion in reply to greg, 12-18-1999 17:35:44  
Greg you will need to replace that piston. Try Two Cyl. Plus Salvage in Conway Mo. Ask for David at 1 417-589-2634. You can set the Rod clearance now before you tear it down but I would check it again when I reinstall the Pistons and Rods. The Gaskets can be bought from your Dealer or you can call Lubbock Gasket and Supply at 1-800-527-2064.



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