Piston Inspection/Assembly/help

[rancher41]

Oh and svcguy. I am really particular on how I take care of my equipment as well. My little tractor is showing terriable cosmetic signs but filters, oil changes and grease it has not seen a shortage of.

Funny thing, when I started tearing it down thoughts of a new coat of paint came to mind. However, the realization hit today ,that right now, I hope just to hear it run again.

If the rebuild works out maybe I will treat to a coat of paint.

 

[svcguy]

I am sure your overhaul or rebuild will work out just fine. In fact, anyone doing their own work will almost certainly be happy with the result if they are careful. The chances of a poor job is almost impossible if you follow the instructions in a manual and use the manufacturers recommendations. I wouldn't worry too much about the burn, but ensure it has no high spots before reassembly and would recommend using a high temp sleeve retainer like Permatex or an equiv. This is a space age plastic that seals between sleeves and the block. You can read more at:

http://www.devcon.com/techinfo/HI TEMP SLEEVE RETAINER.pdf

If you have removed your sleeves, you will need to replace them. I am not sure what you mean by honing out. You don't want to hone the block after removing the sleeves, but will want to lightly hone the new cylinders to ensure for a good ring seal if they are not honed already. When replacing your sleeves, watch your surface rise on the sleeves. Your engine may call for it and may not. It has a lot to do with sealing the head gasket. Search the internet for examples of a good, 'light' crosshatch before honing. Don't hone too much. You want enough to seat the rings, but this is a lightly honed surface, barely able to be felt with your fingertips. I find the ball hones work well, but don't over do it. I have seen some pretty enthusiastic honing, where the person would have been better off leaving the original cylinder in place. An original .008 taper isn't impossible to work with, but I have seen people hone .010 off a new wall by not understanding the idea of breaking the glaze on a cylinder. I would make sure the head is in good shape before replacement. If you had excessive ridge, the chance you need new guides is pretty high and at that point, clean up the valve margins. Don't lap your valves, either reface them or take them to a shop to do it for you. You can easily see if there is excessive wear on the crank journals by using a micrometer to measure them. At the very least, check the new bearing clearance with plastigauge.

Cheap Way to Measure Bearing Clearance

This will remove any doubts you may have about the bottom end. And check all your torques at least three times, that way you won't obsess about them afterwards. You sound like a very capable person, I am sure you will be fine.

 

[MJPetersen]

Machinist said check rod bearings for copper color. Sure enough. He said this could indicate crank journal excessive wear. What do you think?

Jim, No reason to be discouraged. This may turn out to be one of those projects where your initial thinking is that you want to go a yard but since you are there you might as well go another step and since you are already this far then another and another--We have all been there. I have done it more than once on an engine rebuild too. Initial thinking rings and then a complete rebuild at the end.

However, a little "copper color" does not necessarily mean it is necessary to turn crank. You should mic the rod journals to find the smallest size and the largest. The difference will tell you your out-of-round (the largest and smallest will be 90 degrees apart). Yanmar has a spec for that too. if it is within tolerances then new bearings and go. If it is outside the specs then turning and oversize bearings are necessary. The top rod bearing and the bottom main will be worn.

Do not hone the bore for the cylinder liner! Just carefully remove any high spots, maybe with a dremel tool. I do not know how thick the walls are, but the cooling jacket is behind that wall and you do not want to put a hole there or your block will be junk. I do not recommend honing because you want a tight fit and do not want to enlarge the hole at all. The dry sleeves rely on the tight fit for the heat transfer and you do not want any relative movement of the liner to block.

Take heart and just push ahead!!

Mike

 

[rancher41]

Appreciate the comments fellas. I will let you know what I find out. I feel much better about the project and going out to work on it today after reading you imput.

Jim

 

[rancher41]

Crank measured (with plastitape) .002 with old rod bearing. Machinist says that should be ok!

Noticed copper colored gunk in oil pan while cleaning it today?
Not sure what that is?

Parts will be here tommorrow and head might be done.

jim

 

[svcguy]

Interesting question and one I wish I could answer. Over the years I have noticed what seems to be very fine copper suspended in oil after a change (if viewed in sunlight). No one has ever been able to give me a definitive answer as to what it is. Have been told it's an acidic reaction with heated oil, bearing failure and all kinds of other stories. I have seen it in tractor, truck, car, motorcycle and airplane oil, none of which ever failed to my knowledge. Don't know if that is what your copper colored sludge is, but my YM240D manual actually calls for removing the pan and cleaning it out every 300 hours.

 

[rancher41]

Would it be ok to VERY lightl hit the block cylinders with the hone just to clean them up?

What are the chances my oil pump and injectors are bad?

Bought one new injector thinking I was getting all three. Should I return or buy two more.


Jim

 

[rancher41]

Oh yeah, any advise on installing the piston bushings. I do not have special tool shown in manual. Heasd will not be ready until next week.

While the crank journal speced ok, I hope the main bearings don't come back to haunt me. I am about out of time and money for repairs. Any thoughts?

Jim

 

[art]

I see a lot of good info on a basic rebuild. Every engine has it's own specs that are more important. If you are to hone the sleeves then let them be in the block! That is the same as boring or honing with a plate to simulate the torque of the head bolts being torqued down which is a must.They do change you know! With a diesel to make it start good I like to make sure the valve protrusions are right.

 

[svcguy]

Jim, I wouldn't worry too much about your mains if the rod bearings weren't bad. As a rule, your mains will hold up much better than the rods. As for the block, I really wouldn't advise honing before inserting the cylinders. The block will be machined to fit the cylinders perfectly and I just wouldn't recommend putting a hone to them. Clean the block really well of any contaminants, ensure any nicks are smoothed and leave it at that.

I doubt your oil pump will cause you any problem if it was working before disassembly. Injectors are a different story, but wouldn't worry at this time unless they were suspect to begin with. You can change them out easily at any time. There is no end to what you can spend, but ask yourself this - if you could have run it another 6 months or a year without the rebuild, would you have changed them out? I doubt it. I would reassemble with close attention to torques, triple check everything before closing up and see how it runs. You will have plenty of time to change out the injectors if necessary.

Not sure what you mean by piston bushings. Are you meaning wrist pin bushings in the rods?