L2250 spun bearing/rebuild

[LovesDauphins]

Can someone help my newbie eyes please? I believe after watching some videos that I have the signs of a spun bearing. Video of me checking the first cylinder that was knocking is attached: https://youtu.be/vqKG-SwZ9Q4

So as I began to tear into the engine....

1) Is this carbon build up unusual that's in the exhaust ports?


2) I notice rust on the valve springs - unusual? I feel like I see metal shavings and water or some type of sludge mixed in with the oil. When I drained coolant it was green as Spring grass...?




3) 1st cylinder (my failing cylinder) is on the left. I don't know what to look for on these cylinders but the #1 is black...#2 and #3 are just grayed out and not nearly as built up with carbon.


Thanks for looking!
Brandon

 

[motmow]

You need to pull the oil pan and remove that piston to see what the damage is, but it does look like a spun bearing. If so, you are going to have to pull the engine out of the tractor, because the crank comes out the rear. if its not to bad a machine shop can grind it and polish it smooth and you will have to rebuild with over sized bearings. good luck.

 

[North Idaho Wolfman]

I would bet based on colors and markings that that is a head off a different engine, the rust probably was from it sitting out, how did the valves look?
The carbon is a little heavy, while you in that far, pull all the rods and pistons and replace rings.
If you want to make sure you don't have an issue, have the head gone through and maybe a valve job.

Note:
Wet piston tells me it's not firing, and that alone will give you knock!

 

[Diydave]

Rust on the valve springs is can be common, if the engine has been run too short of a time, to get up to operating temperature. as others have said, pull the crank, so you know how bad the damage there is...

 

[LovesDauphins]

I'm back - I feel like a jerk asking for help and not replying/thanking everyone. You guys are more of a help than you realize! It started with getting called into work the day I posted the question and a couple of double shifts ...anyhow back to a normal schedule:

Took quite a while to disassemble the tractor and separate it. Pulled the motor and the pan....spun bearing on #1. Bearing was in shreds in the pan. This ain't going to be a cheapo..haha. new injectors, rings, bunch of misc parts that were rusted and broken as I disassembled...and no idea what the damage will be to the crank. Fun stuff learning how to do this though....




Going to try and pull the crank tomorrow for closer inspection before I head into work. I'll post those pics..thankfully vacation starts Friday so there will be time to work on it.

Link to more pictures-http://s110.photobucket.com/user/dauphinpilot/library/Kubota

 

[Tooljunkie]

So that knock was definetly the sound of parts trying to break out....glad you are making headway.

 

[LovesDauphins]

Thank you - I feel even better after yesterday.

I was able to remove the crankshaft. That was a somewhat complicated task... I didn't realize it was that tough to pull a crank shaft out of an engine. Although it was my first time. I ended up having to air chisel that 46 millimeter nut off the front. I also didn't know about the feather key and how it was removed.

I don't think the crank looks too bad. I dropped it off at a machine shop yesterday afternoon. I am attaching pictures if you good folks see anything that looks out of the ordinary please let me know. I did notice that the timing marks didn't match up is that a problem? It also appears the only damage was to the number one cylinder part of the crankshaft. The rest of the crankshaft feels very smooth and looks good. The oil galleys do not appear to be plugged. And the shaft does not show any signs of bluing or heat issues that I can tell



Close up of #1



Close up of the timing marks on the idle and cam gears



Now...I'm trying to get a grip on costs. I'm thinking it shouldn't cost too much to grind everything down that needs grinding which should only be the affected area on the crankshaft and rod. I was shocked to see that a new rod is $188. And a set of rings are $88. Am I right that a used D 1302 would be around thirty-five hundred bucks? I'm just trying to make sure that I shouldn't just buy a new motor as opposed to fixing what's there but I believe I can fix this for a lot cheaper than a new motor. The motor seems young -approximately 1200hrs...

 

[rbargeron]

Doesn't look like you need a ton of parts. The crank will clean up fine - even the rod might be usable if checked for non-binding operation assembled in the block with new bearing shells. Check your oil pump for internal debris and wear and make sure the oil passages in the block are clear. Was the initial bearing failure due to running low on oil? Repairing this engine should be a lot cheaper than replacing it.

 

[LovesDauphins]

I think it was a combination of low oil and finally giving up after years of neglect. I knew that it was low on oil but I didn't think it was out of oil or enough to calls the bearing to just break one time. The previous day it was run hard during the blizzard for about 6 to 8 hours but I'd run it several times like that before in the yard. I was hoping to make it until February when it's really cold around here to do the tear-down, rebuild, "help it in whatever way I can"....

They did mention cleaning the block at the shop and pressure testing. I'll see how much they want for that. I might do that just to make sure all the passages are clear unless someone can tell me if there's an easy way to do it.

 

[LovesDauphins]

Also, I am trying to figure how the bearing size or part numbers work. I've got the WSM and the parts manual...but I'm trying to figure it out? The machine shop told me he doesn't always deal with Kubotas...he usually has Chevy etc...so I'm dropping off the specs I found in the WSM...I was looking the part numbers up on Messicks but they aren't coming up.

 

[Diydave]

I'm not so sure that it's "not that bad". It doesn't take much non lubricated wear to mess up a crank. Not real sure what undersize bearings are available, either. Wait till your machinist get it cleaned up, mic'd, and tells you how much he has to take off, then talk with parts man, and see what's available, parts wise. If the undersize bearings are available, THEN count your chickens...

 

[LovesDauphins]

DIYDave - your right....just trying to stay positive...I feel alone without my best friend running!

This is where I definitely need some HELP /guidance from you guys... Finally got my phone call today: Machine shop says it cleaned up to factory specs with some minor pitting - bearing basically melted to it. He would like to grind it down further though to eliminate the minor pitting. I made copies of the WSM for him with the specs.

He had a question about the oil clearance between the crankpin and connecting rod. WSM says allowable limit is .0079...he felt that was way too much. I don't have the know how to tell him what is right or what isn't...although I am reading and trying! I noticed what the factory spec is a lot less and I think that is what I would be shooting for. He was also asking about the outer diameter of the connecting rod where it meets the crankshaft. He was able to clean that up but I am trying to decide whether to just bite the bullet and buy the new assembly for $188 (Part #17311-22310)I think we are trying to piece together the bearing sizes.

Also is it better to just grind all 3 crankpins to the same spec? I can't get a PDF file of the WSM to attach - too large. Took pictures of the manual and attached as pictures - tried rotating it and it was fine on photobucket but not here for some reason.

Kubota offers bearings (called "metal crankpin"?) 17331-22970 -2mm and a -4mm.

 

[Jim L.]

In general, I would want the same oil clearance on the 3. With the same oil pressure and same viscosity, that would give the most even lubrication.

So I would measure the oil clearance on the two good ones. Then take off enough material on the shaft to get rid of the pitting, and knowing the bearing diameters to trim the shaft to match an available bearing to bring all into close agreement on oil clearance.

As previously said, clean up of the oil pump and passages essential.

 

[North Idaho Wolfman]

He had a question about the oil clearance between the crankpin and connecting rod.

I think the answer he is looking for is the .00098 to .00343 in.

 

[LovesDauphins]

Thanks for the replies guys! I stopped by the shop and saw the crank which after being cleaned up is at the very bottom of the factory spec....The crank will be ground down though and will get the next size bearings for all three. The pitting was borderline from what he said - so we are erring on the cautious side.

Getting my shopping list together of replacement parts and ordering it all. Just a matter of waiting - I'll keep everyone up to date.