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Rod Knock ?


clyde

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I picked up this thing awhile back thinking I would try and use the hydraulic lift on my Landord or 712. It is a Case 224 with a Kohler K321A 14HP engine. I pulled it out last night and got it running. It has a rather loud rod knock - at least I think it is a rod or bearing type knock. The reason I'm not sure is that is seems to 'come and go' and when driving up hill, where the engine was under load, it went away completely. Would this happen if it was a bad bearing / rod/ etc? TIA, Clyde.

BTW, someone had done a nice job of repainting it at one time (even if it is green) The designs and pin-striping are all painted on.
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quote:
Originally posted by clyde
.... Would this happen if it was a bad bearing / rod/ etc?
Yes it could....... find the problem now and fix it before major damage is done.
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Clyde, If it is a rod knock, there is an easy fix that most people on this site will probably scream about. I have repaired a couple this way with good luck. First find the clearance specs between rod and crank. Buy some plastigage and check the actual clearance. File a small amount of metal away on the seating surface where the rod and cap contact. Re-check with plastigage. To do this check the cap must be torqued to spec. Re-do the filing and checking till the clearance comes within tolerance. I have done this on a couple of engines that have run for years afterward with absolutely no problems. Just do not get the clearance too tight or it will sieze and possibly break the rod. The cap is somewhat flexible under load. I would try to remove metal from only one end of the cap, so that the other end can keep it sitting squarely. Always check the clearance between the rod and the crank. The small amount of flex in the cap can give a false reading that will indicate less clearance than you really have after torquing the assembly, while the rod is very rigid and will compress the plastigage correctly. Other alternative is to replace the rod and crank. Your choice if you would like to try it. It has worked for me, but I am not saying it is a method to do in all cases. I have used this technique only on a couple of engines that were not worth re-building, yet I had excellent results. It is not much difference than checking clearance and using different thickness bearings on an automobile engine as is done in race engines. I did this on a 2300cc Mustang engine after rod bolts came loose and mangled one of the bearing caps. I replaced the cap only from another rod, but since the rods are bored as an assembly, there was too much bearing clearance with the new cap. I had to tighten the rod bearing clearance, and didn't want to pull and re-build the engine from a car that was worth less than the cost of a re-build. We changed the cap and tightened the clearance by removing the oil pan and working from underneath. We drove the car daily for over a year before trading it off. Had good oil pressure and no knock. I also tightened a rod on a rototiller and used it for four or five years before giving it to a friend. OK, everyone, I have just opened myself up for a bunch of criticism. Let me hear it.
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Take off the head and see if there is a carbon build up and an impression of a piston in the fire deck. This also has been a source of rod knocking. If the engine has never been taken apart, there's a remote chance that you could do some de-carbonizing. Hold off on Rod's recommendation and pull the head first. Then if there is a knock still present go to Rod's suggestion.
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Thanks Guys, I don't plan on starting it again after my little test run. I just haven't decided what I'm going to do with it yet. Rod, your suggestion makes sense to me - I picture rod bearings wearing more on the top (towards the top of the piston) and bottom (towards the oil pan) so filing the ends of the rod cap would actually put it back 'in round'. I'm a couple up on the 'honey do' list (very short term situation:D) so I may get to spend some time on the tractor list and pull it apart this evening.
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CLYDE, I HAVE NEVER HEAD OF FILING THE ROD CAP BEFORE, BUT LIVE AND LEARN.YOU DON'T HAVE ANYTHING TO LOSE BY TRYING IT. AND IT MAY WORK AS LONG AS THE CRANKSHAFT DOES NOT HAVE A FLAT SPOT ON IT.THAT IS WHAT HAPPEN MOST TIMES, IN MY YEAR OF REBUILDING V.W. ENGINES, AND SMALL ENGINES. GOOD LUCK. LET US KNOW HOW IT TURNS OUT. KEN
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when filing caps; take very little off. Then use plastigage to monitor how well you are fitting cap to crankshaft. You can also get new oversize bearing and fit that also, may not have to file cap. Should consider cap filing last resort.
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As I started to take the engine apart it was obvious it had been dis-assembled fairly recently. Head looks new (or really clean):

Pulled the engine out and off with the pan. A little bit of metal in the pan: [img]/club2/attach/clyde/eng2.jpg[/img] Rod was pretty loose on the crank and when I pulled the cap it looks like this: [img]/club2/attach/clyde/eng3.jpg[/img] And what you can't see is a big hunk missing out of the bottom of the cylinder. The rod looks 'newish', so I suspect someone has replaced it once - probably when the previous one broke the cylinder wall. Guess this makes up my mind - I'll keep the hydraulics and part out the rest!
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The whole tractor looks like it'd be a nice project. They're nice to use too. Looks like you have a newer model with the hydraulic lift by the steering wheel. It looks like a nice tractor. The paint looks alright too.
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