Kubota L4740 Engine "knock" Help?

[TMGT]

Re: Kubota L4740 Engine "knock" Help?

Check in the Items For Sale section, member Harry in Ky was parting out a V2403 that has spun a rod bearing from being low on oil, block might be good though. Said he was scrapping it in a few weeks so might be gone already but worth a try.

Can't remember but thought the L4740 used the V2403

 

[jshwhite]

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!

 

[crazyal]

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?

 

[ericm979]

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.

 

[TMGT]

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?

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.

 

[TMGT]

Re: Kubota L4740 Engine "knock" Help?

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.

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.

 

[pmsmechanic]

Re: Kubota L4740 Engine "knock" Help?

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.

And it depends on if it can handle the heat in that environment. If it can it's also a good choice.

 

[TMGT]

Re: Kubota L4740 Engine "knock" Help?

And it depends on if it can handle the heat in that environment. If it can it's also a good choice.

-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.

 

[TMGT]

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

 

[pmsmechanic]

Re: Kubota L4740 Engine "knock" Help?

-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.

I'm with you on a different block and I'm with you on the above quoted text also. I don't think the pounding is any different on a gas or a diesel. Engineers size the bearings to take the load.