Kubota L4740 Engine "knock" Help?

[jshwhite]

From what I understood, maybe this is an old thing now, is that to get the gap between the rod and crank correct you just file the end of the rod down. When the ends meet while tightening up the bolts the bearing ends meet and compress the bearing which makes it thicker. Maybe now to make things simple and because the machining process is much tighter the bearings just fit.

I talked with a local machine shop years ago about connecting rods that spin bearings. Obviously a rod can be replaced easier but in some cases they would recondition them by shaving a few thous off of the cap and then reboaring the rod. One of the other things they would do is use a thicker bearing. There's nothing magical about them. If it's designed for a larger diameter (which is what you want) they just shaved the end off and bent it to match the crank. As long as it fit tight, it was the right width, it had the oil passage hole in the correct spot, and the gap between it and the crank was correct it would work. It's more messing around on the mechanic's end vs just putting in the correct size but it can be done. I suspect that if this is correct it would work with a main as well.

Did anyone actually measure it to see how much larger it is compared to the other mains?

Yeah this one is a bit newer/different. Actually if I'm not mistaken the front main is different size than the others (it's a different part reference on the diagram), so comparing them wouldn't help much.

Instead of JB weld you could use one of the LocTite products made specifically for filling in gaps between parts that are supposed to be a press fit.

Thanks for that pointer. Will check into that.

For all the other bearings this would work, however this happens to the the 1 bearing that does not use a split bore.

A lot of manufacturing has gone to a cracked cap design for the connecting rod big ends, this requires boring and oversized bearings since the mating surfaces the rods big end cannot be ground down.

Exactly. Don't have the same options you would have with a split bearing.

Loctite 640 sleeve retainer is what I'd probably use for this, use it regularly but never tried it on a main bearing. Depends on how lose the tolerances are.

-65 to 400F, should be good, the only worry I have is the pounding a main bearing can take on a diesel.

If the fit is too lose I wouldn't trust anything other then boring and sleeving back to size.

Agree. Just waiting for the new bearing to come right now. Will check the fit when I get it and go from there.

Although I would see if that one used block is still available first!

I messaged Harry in KY and he said the block is bad unfortunately. Something about it having to be "ruined beyond repair" for Kubota to replace the engine. Thanks for the lead though...

 

[TMGT]

Re: Kubota L4740 Engine "knock" Help?

Well that's a bummer, since it was a warranty deal most likely they had to drill holes in the block so it was unusable. Heard it had something to do with manufacturers liability for new tier3 engines after tier4 implementation, has to be a 1 for 1 deal I believe.

Or it was already destroyed enough (ie. it made its own holes!)

 

[ruffdog]

If the bearing bore is mostly there and near size, Loctite 680 bearing retainer is a super product. It has a 4000lb shear and will fill up to .015" voids. Like I said, if the bore isn't too bad, and it doesn't seem it is, I would trust using 680 as a permanent repair.

 

[TMGT]

If the bearing bore is mostly there and near size, Loctite 680 bearing retainer is a super product. It has a 4000lb shear and will fill up to .015" voids. Like I said, if the bore isn't too bad, and it doesn't seem it is, I would trust using 680 as a permanent repair.

The only thing I'd worry about with the 680 is its only rated to 300F, which while its higher then most oil temps, is a little closer then I'd like.

 

[sixdogs]

If the bearing bore is mostly there and near size, Loctite 680 bearing retainer is a super product. It has a 4000lb shear and will fill up to .015" voids. Like I said, if the bore isn't too bad, and it doesn't seem it is, I would trust using 680 as a permanent repair.

The only thing I'd worry about with the 680 is its only rated to 300F, which while its higher then most oil temps, is a little closer then I'd like.

Call Locktite and speak with tech dept. Ask questions. I did that on something last week because I needed help with a situation and they helped me out. A woman answered the phone and I got a little suspicious but she really knew her stuff.

 

[ruffdog]

The only thing I'd worry about with the 680 is its only rated to 300F, which while its higher then most oil temps, is a little closer then I'd like.

Yeah, if your oil is over 300F, you're going to have more than a few issues.

Why use a retaining compound? | Machine Building

https://www.tractorbynet.com/forums/kubota-owning-operating/370683-l4740-hst-engine-knock.html?highlight=l4740

 

[fried1765]

I love the old time solutions! These days they just throw new parts at it and don't bother with the effort to fix it.

I wouldn't have thought of JB weld, but that's a good idea. I guess as long as you were careful not to get it in the oil channel, it wouldn't hurt.

Alien, I'd never heard of metal spraying before. Looked it up on YouTube. Quite interesting!

I had 2 marine engine shafts sprayed 25 years ago.
Then had them turned to spec.
Worked out well.

 

[ericm979]

Loctite makes a lot of retaining compounds. Call them and ask, or read the specs.

Did you find out what caused the lack of oil to the bearings?

 

[The Fred]

Call these guys and ask about a complete kit for your engine, usually $1500 bucks or so all real Kubota parts, stay away from Kumar Bros parts, all junk ask me how I know!

These guys are the best and far cheaper than buying from your tractor dealer.

Kubota Diesel Engines | In Stock New or Remanufactured Diesel Engines

 

[jshwhite]

Got the bearing yesterday. Fits like new. I'm going to call Loctite and see which compound they recommend and put that on for good measure.

Next up is order the rest of the parts needed, then will clean the block, check/test all the oil passages, and press the bearings in.

Thanks for the tip on countrysales. Will check out their rebuild kits.

Can anyone tell me where to find the serial number on this engine? Some of the gaskets have a serial number break. I can't find it though.