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Discussion Starter #1
I just inherited my deceased grandfathers 1978 JD 312. It's been sitting for a few years now. The last time I saw it run, it was smoking pretty bad and blowing the oil dipstick out, and blowing oil everywhere. I haven't started the engine yet, but I did a compression check, and I read a consistant 120 psi(no wd-40 or oil put in the cylinder). Think it needs rings, piston, and valve job?

Any ideas out there?

Thanks,
Ryan
 

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Maybe your breather hole is plugged in the valve chamber...
I dont think 120 psi is that bad...
 

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Below the carburetor is a square cover. One bolt holding it. It has a vent. Under the cover is usually a fiber suare that is supposed to catch dirt on its oily fibers. Clean it and oil it, make sure the vent hole is open.
 

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Discussion Starter #6
sounds good guys. Thanks

I'm going to order the operator and service manuals today...

I'll have to post some pics soon of my little project....
A few years ago I "restored" a little JD 111, and she still runs looks great! So this will be number two....

thanks for your help

Ryan
 

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Discussion Starter #7
FOUND IT! Sorry I'm not much on mechanical terms. But usually once I put my hands on it, it all makes sense! :)

Dirt dobbers had totally plugged the rubber tube going into the carb breather area!

Check out my new posts with pics...give me your opinions, and advice!

Thanks,

Ryan
 

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Discussion Starter #8
PLEASE HELP K301 smoking bad!!!

OK. I just got the tractor somewhat assembled, but I got it running. Kindof a preliminary test run. I just piped and wired up the basics until I see what I'll have to tear back down and repair/replace. Cleaned carb, ect....

It smokes like crazy! Blue smoke= OIL burning! I did a compression test after it got to normal temp and it read about 129 PSI. According to the service manual, anything between 110 and 120 PSI is good. ****, I got 129 PSI. :) Now I think it's my worst fear...valve problems!:praying: I've read that worn valve guides can cause it to smoke/burn oil?

PLEASE HELP!:praying:
 

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That would be my first action--immediate oil change in any engine--especially one sitting or not sure of....Add a couple teaspoons of MM Oil--and change it again after a couple hours of hard use....Fresh gas!!

Put in a new spark plug/like said--clean the breather vent out good--make sure there is a clean air filter on it..

Lot of little things--but any and all can cause problems....:goodl:

glenn
 

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Discussion Starter #12
Thanks Glenn. I've taken this tractor down to the frame. Replaced all fluids, a few gaskets, breather filter, cleaned carb very good, ect. I even bought some $9 SeaFoam and drizzled it into the carb with it running. But still got lots of oil burning smoke.???????
All I can guess is the valve guides are worn very badly, allowing oil to get into the combustion chamber? B/C i have tons of compression!
 

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Figure on a piston and rings replacement. You still have good compression because the oil is helping to seal any compression leakage, and carbon deposits from oil consumption have probably slightly increased the compression ratio.
 

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Discussion Starter #15
thanks rscurtis.

I just pulled the head off tonight and lots of carbon! But everything "looks" great. I see a 010 on the piston, so I'm pretty sure it's been rebuilt before 010 oversize. I'm going to take some cylinder measurements tomorrow.

One thing I did notice is the piston can move side to side just a little bit. Enough to see it noticeably?
 

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Discussion Starter #16
Update, the piston is pretty loose in the cylinder. I guess the piston is worn, but not the cylinder?? The cylinder is pretty much in spec, but the piston has like 1mm of clearance to the bore?? I guess a worn out piston?
 

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Discussion Starter #17
well, I removed the piston and took some measurements. One thing I don't get is the service manual's cylinder bore specs. It says something like 3.38 inches new, but then says that the out of round and taper of the bore has to be within .005 The bore spec doesn't even go into the thousands place??? Again, the cylinder is .010 over and the crank journal is .010 undersize. But back to the measurements. Nothing is way out of wack, the bore measures almost perfect. The piston isn't that bad either. The rings look great too. The only thing I wonder about is the oil ring. It doesn't spring out like the compression rings at all. What should a good one look/measure like?

thanks again guys!

Ryan
 

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Push a ring into the cylinder with the piston (so it is in squarely), and measure the end gap with a feeler guage. If it is more that .004" per inch of cylinder diameter, the ring is worn. I think you'll be surprised at how much ring wear you will find.
 

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Discussion Starter #19
one more silly question before I take it to the machine shop. Does anyone have a picture of a newly installed oil ring? I think mine is broken or something. The service manuals have terrible pictures in them. I found a couple pieces of what looks like plastic that was broken on the oil rings...

thanks!
 

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Discussion Starter #20
Proper oil control ring installation?

Here are a few pictures of the piston and rings. I would think that the "oil control rings" should protrude out just like the compression rings? Mine has two very thin "rings" and a "spring" underneath them. But the rings do not spring out?

thanks!
 

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