Kubota L4740 Engine "knock" Help?
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pmsmechanic
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Re: Kubota L4740 Engine "knock" Help?
Either the front oil passage is blocked/partially blocked or someone sat the tractor on it's tail with the engine left running.
Either the front oil passage is blocked/partially blocked or someone sat the tractor on it's tail with the engine left running.
TMGT
Elite Member
Blockage would be my first guess also, depending on how the oil is fed it could be some other things.
Just like to find root cause so history doesn't repeat!
Just like to find root cause so history doesn't repeat!
jonsstihl
Veteran Member
sorry to see that. looks like a bunch of casting flash to me but I have no first hand experience rebuilding engines.
Hilbilly
Veteran Member
Very interesting thread and thanks for taking the time to document your journey and taking pics. Not really something a guy wants to do when he's dealing with problems.
Sure glad you have the skills to do this yourself.
Sure glad you have the skills to do this yourself.
Gregster613
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I second all that Hilbilly said! Very informative and well documented thread. I'm glad that you have the skills. space, and equipment to do this yourself; saves you mucho $$ on labor. Great job.
crazyal
Super Member
Really makes you think about getting Kubota insurance when you buy a used tractor. It could have been just bad timing or it could have been the previous owner knew something was wrong (or he did something wrong) and sold it to avoid a big repair bill.
Agree completely. Definitely will clean/check every oil passage. Also replace oil pump and pickup.
I guess misery loves company
Sure is nice to bounce ideas around and get other thoughts. Not sure about the skill level, but I'm always up to learning something new. It's what you have to do when you don't have a bunch of money to throw at it. Necessity makes a great teacher...
I really do wonder if the previous owner knew something. Especially since he sold it at a really good price. I thought I was just getting a good deal, but I guess you get what you pay for.
So I talked to the Kubota service department and their recommended machine shop today. I misunderstood originally. They do NOT offer oversize bearings - undersize for turning the crank, yes, but not oversize if you need to bore the block. And since there's no cap on that end, there's no way to clip the cap and line bore it. The machinist looked at it and thought it might actually not be too bad and you might get away with just putting a new bearing in it. But obviously the official recommendation from them and the dealer is a new block - $$$
So I took it and showed it to a friend of mine who is one of the best engine rebuilders in this part of the state. He's got lots of experience and is a bit of a legend around here in building racing engines. He's also good at coming up with innovative solutions He said he thinks I very well could get away with just replacing the bearing. Yes the block is scored, but since it's pressed in it might hold.
So I ordered the bearing and will see how it fits. If it's too loose, he said there is a possibility of boring it very oversize and fitting a steel bushing, then the bearing inside that. At this point I'm open to any of that, as the block is junk otherwise.
Considering that a new block is $3500, I'm game just go with a new bearing, provided it's reasonably tight. Worst thing that could happen is I end up right back where I am now.
One other thought I did have: what about finding an aftermarket oversized bearing? Surely there's a company out there somewhere who offers stuff like that. Anyone know anything about that?
pmsmechanic
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It wouldn't cost $3500 to have the block bored and a steel sleeve pushed in. Also if the new bearing is reasonably tight and in alignment with the other bearings a little JB Weld would go a long ways towards keeping the new bearing in place.
If anyone doubts the effectiveness of JB Weld my friend tells of how they would glue broken cylinder liners together on Detroit diesels in the 70's to keep them running till new parts came. And the liners were broken through the windows in the liner that the intake air entered the cylinder through. I would think that would be a harsher environment then just helping keep a bearing in place.
If anyone doubts the effectiveness of JB Weld my friend tells of how they would glue broken cylinder liners together on Detroit diesels in the 70's to keep them running till new parts came. And the liners were broken through the windows in the liner that the intake air entered the cylinder through. I would think that would be a harsher environment then just helping keep a bearing in place.
Alien
Elite Member
I remember we used to get bearings metal sprayed to make them tight. Long time ago. You could also get crankshaft journals metal sprayed and re-ground too.