Well... Here I go with overhaul

Post your questions or problems you are haviing with your Yanmar tractor here.

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gwp
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Well... Here I go with overhaul

Postby gwp » Fri Jun 28, 2019 8:40 pm

Ym2000
Was hoping to do this after grass growing season but oil light (verified with gauge) is now coming on after warm up even at high rpms. Plan to start tearing down tommorow (sat). Would appreciate some affirmation that I'm on the right track. My symptoms are:
*Super low oil pressure... As stated above
*Very hard starting in cold weather (under 60 degrees)
*Very quick starting in warm weather (coastal Alabama}
*Runs very well with very little exhaust smoke
*Quite a bit of blowby
I had head-valves totally reworked a while back and have not done compression test but feel certain I have low compression due to hard starting in cold weather.
Would you suggest I plastigage the rod bearings or if crank looks ok just order stock ones?
Any advice appreciated

winston
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Re: Well... Here I go with overhaul

Postby winston » Sat Jun 29, 2019 4:42 am

If possible I would inspect and measure the crankshaft to see if in tolerance before ordering parts. Same for cylinders and pistons.

gwp
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Re: Well... Here I go with overhaul

Postby gwp » Sat Jun 29, 2019 7:46 am

Will do. I still can't stop wondering if I could have a weak oil pump or bad relief valve (the valve behind the oil filter) I know that is unlikely but sure would like to eliminate this before overhaul only to put all back together and still have low oil pressure. Thank you

winston
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Re: Well... Here I go with overhaul

Postby winston » Sat Jun 29, 2019 10:44 am

Hoye could probably advise you as to how many of those oil pumps they sell. I do not hear of many being changed. I would look over all clearances real close and maybe decide from what you find. It would be quite a job to remove that front gear housing.

gwp
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Re: Well... Here I go with overhaul

Postby gwp » Sat Jun 29, 2019 5:45 pm

Ym2000
Got engine torn down and here is what I found:
*no broken rings
*Though very slight, I can catch my fingernail on one section of one cylinder wall at highest point of ring travel and some vertical scoring on cylinder walls and Pistons.
*Rod bearings have significant scoring.
Being as precise as I could, i am measuring .105" difference in the two crankshaft journals. That's scary. Your thoughts appreciated.
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gwp
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Re: Well... Here I go with overhaul

Postby gwp » Sat Jun 29, 2019 5:50 pm

I'm thinking top end is the least of my problems.
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winston
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Re: Well... Here I go with overhaul

Postby winston » Sun Jun 30, 2019 5:49 am

.105" is nearly 1/8". Hoping you just made a mistake in measuring. I think .030" undersize is as much as you can go.

Your bearings are no doubt shot. You need to get accurate measurements on the crank journals. Need to be measured at different intervals around the journal assuring the crank is not worn unevenly. Are they smooth or grooved?

Looking at wear on bearings and pistons I would be suspicious of your main bearings also. Maybe some gurus will step in here and give their opinion. Looking at pictures is not a fool proof way of accessing what you need to do next.

Getting expensive but if your wanting to put this back in service for the long haul it may be sleeve and new piston time. If you can hand a fingernail that is to much wear and your pistons are grooved pretty bad.

gwp
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Re: Well... Here I go with overhaul

Postby gwp » Thu Jul 04, 2019 10:26 am

Looks like I was a little anxious and way off on measurements. The difference between crankshaft journals is 0.0125. the readings I'm getting are:
Front - 2.1230"
Rear - 2.1105"
I'm not totally confident of my readings as it is very difficult working thru the engine housing.
Anybody happen to know what they measured originally?
The crank journals have extremely light scratching which can be seen but barely felt so I wouldn't consider them "grooves". I'm feeling better about the crank but still inclined to split tractor and replace main bearings and further inspect the crankshaft. I only want to do this once. Used to have an old Ford Jubilee which I had to split to replace ring gear and clutch but never gotten this deep with crankshaft, etc. I read that the shop manual is not specific to the ym2000 so I'm hoping it will not be a waste and help guide me thru the project. Nice having the resources on this site. Thanks

winston
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Re: Well... Here I go with overhaul

Postby winston » Thu Jul 04, 2019 10:51 am

Crank journals 2.124-2.1246, wear limit 2.12241

The 2. 123 is allowable, the other journal if turned to a .010" under would still be nearly .002" out of specs.

Did you check the journal for roundness? If journals are worn they are likely not round.

gwp
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Re: Well... Here I go with overhaul

Postby gwp » Thu Jul 04, 2019 11:47 am

Thanks Winston. Well.... There you have it. Will definitely have to tear down. Gonna show my ignorance and ask......
Can a journal be built up or will crankshaft need replacing?
Hoye lists a new one for $+500. If it can be built up should the machining labor exceed this?
Was shocked to see that a new one can be bought... Which is good news even at the cost. If already known to be out of specs and the likelihood of main bearing wear, further tear down is inevitable. Agree?

winston
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Re: Well... Here I go with overhaul

Postby winston » Thu Jul 04, 2019 1:55 pm

Crankshafts can be turned to undersize. Note the bearings sold here. Main bearings: https://www.hoyetractor.com/PROD/MB-525.htm
Rod bearings: https://www.hoyetractor.com/PROD/RB-45.htm

Machine shops that do this work will need this information.

I am not telling you this is what you need to do. Just giving you tolerances and parts advice. On sight inspection and determination as far as how you proceed.
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gwp
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Re: Well... Here I go with overhaul

Postby gwp » Fri Jul 05, 2019 7:14 pm

YM2000 - removing crank shaft
Thanks again Winston. Waiting on shop manual but thought I'd get a head start. I have removed radiator, alternator, hydraulic lines and everything necessary to split tractor exposing both ends of crank. I am assuming I can avoid removing engine from frame by jacking up both sides of tractor and pulling apart. Gotta get a plan for that honking flywheel nut.
Am I on the right track here? Anyone's advise appreciated. Thank you

winston
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Re: Well... Here I go with overhaul

Postby winston » Sat Jul 06, 2019 4:50 am

I have not done it but looks to me like the engine will have to be removed for crankshaft removal. The I&T manual says to remove the engine. If you have a Yanmar shop manual coming it should cover that.

jimjumper
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Re: Well... Here I go with overhaul

Postby jimjumper » Fri Jul 19, 2019 8:18 pm

I'm not going to be any help but it would be greatly appreciated if you would keep posting about your progress. I going to do mine this winter and since I am pretty clueless what I am doing, the info and pics you are posting is really informational. I also think with over 400 views so far, that a lot of people are watching for the same reason.


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