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Discussion Starter · #1 ·
Last summer I rebuilt my Kohler K321 from my JD 314 Lawn Tractor due to oil consumption and powerloss issues. I noticed when I removed the piston that the upper edge of the piston that faces the intake and exhaust valves had very heavy wear. Infact, it almost looked gouged or filed off at a sharp angle. Anyway, I did my rebuild, bored out to + .20 and began using the tractor again. Everything seemed to work fine, but then I started losing power (after about 20+ hours of operation). I opened up the engine this weekend and found the exact same type of wear on that top edge near the valves. Its not very bad yet, but I'm sure it will get worse. Does anyone have any idea what the root cause for this wear could be?
 

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Discussion Starter · #2 ·
Last summer I rebuilt my Kohler K321 from my JD 314 Lawn Tractor due to oil consumption and powerloss issues. I noticed when I removed the piston that the upper edge of the piston that faces the intake and exhaust valves had very heavy wear. Infact, it almost looked gouged or filed off at a sharp angle. Anyway, I did my rebuild, bored out to + .20 and began using the tractor again. Everything seemed to work fine, but then I started losing power (after about 20+ hours of operation). I opened up the engine this weekend and found the exact same type of wear on that top edge near the valves. Its not very bad yet, but I'm sure it will get worse. Does anyone have any idea what the root cause for this wear could be?
 

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MARK ,a few things come to mine ,the engine might be over heating ,do to point setting .020 this would do it ,and how much clearance ,dose the piston have ,and do you mow in a hilly area,,lack of oil ,if the tractor is leaning to much ,and is the air over the head being blocked .hope this helps David
 

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...also check that the fuel/air mixture is not too lean, as that is another possible cause of excessive EGT and heat build-up (and hence the metal erosion of the piston.)

Chuck
 

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Discussion Starter · #6 ·
Alright. Thanks for all the advice. I'll check the points for clearance (.020") and verify that the fuel mixture isn't too lean. Here's some interesting developments though any maybe there's something more going on here...some background info first. I had bearing inserts installed in my connecting rod because the crank was beyond the wear limit for the (.010) undersize. I ended up going (.020) undersize on the journal. The picture at the bottom shows the part number if any one is interested in having this done.....anyway, I'm noticing irregular wear patters on the bearing inserts. The top and bottom half of the shells have wear on the opposite sides (when assembled) which makes me think that the piston might not be moving true with the cylinder. The picture might help?bearingwear.bmp (62.3 k) What might cause this irregular wear pattern? If the bore isn't true I've heard this could cause the problem. Could my connecting rod main bearing be out of true with the wrist pin since I had it bored to fit my insets?
Has anyone had any experience like this in the past?
One other quick note....when I pulled the bearing plate off, it came off really easy, almost no pressure at all. Shouldn't I need a puller to remove the plate?
Thanks for your help.
 

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Mark,i believe this yet another ,of the kohler things that the block is not true,to its self ,i,ve ran into this as well ,first as far as the rod goes ,when they bore rods they are set up on a fixture,when they are bored ,so they ate true, i don,t believe the bore is true with the crank journels in all blocks ,you ask about the bearing plate being loose ,and not needed a puller ,if the bore for the bearing is oversize .you could, get this pattern,and if the bearing plate its self is loose in the block ,you could get this pattern as well .you would need to have them miced to know this .and if either part is over or under size the can be repaired .the bearing plate could need to be set up in a lathe .and a insert placed in the old bore ,and the od of the bearing plate ,need to be spot welded or up set by peening .fit and re machined to fit the block.so as you can see this would take time and money ,hope this helps . David
 

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Discussion Starter · #10 ·
This picture shows an interesting gap between the cylinder and the wall. You'll notice that the clearance between the piston and the cylinder near the valves is much smaller than the clearance that I point to with the arrow.
Any ideas?
 

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MARK ,when you installed the rings ,can you remember where the ring gap was ..i hope they were 120 degrees apart.,meaning not all on one side .after all the clearance is going to be where it is .i din,t think i would worry about where the piston is right now ,hope this helps David
 

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looking at the pictures and thinking about the "mechanism of damage" - the piston has to move to the side to be damaged so either the wrist pin is "loose", the rod/crank connection is "loose", or the whole crank is shifting - other thought, shouldn't the rings be "centering" the piston?
sorry about all the " "s but since I don't have a more technical explanation, I use "
 

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Discussion Starter · #14 ·
Both the wrist pin connection and the rod/crank connection are a good fit, but the crank on the other hand could be shifting in its bearings...definitely a possibility. I did notice that the bearing plate came off with ease (didn't need a puller)...possibly loose bearings? The only other thing I can think of is that the bore isn't aligned "true" with the crank. I'll find out tomorrow from my machinist what the prognosis on this stuff is....You make a good point though, i normally would think that the rings could provide enough outward force to center the piston (though they shouldn't have to).
 

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MARK .the only real way to check all of this is to set up the block in a boring mill ,on a turn table .and dial the bearing bores .on both ends .because the bore on the bearing plate end would need to be done by its self .to be sure it is true ,and not over size .and or out of round ,so before this takes place .you would need to dial the fit in the block where the bearing plate fits ,and once you dial the block ,he would need to turn the block 90 degrees and dial the bore at top and side ,to be sure it is true with the rest of the block .and if not the block would need to rebore the bore for the piston ,but now that you have the bore .020 it don,t leave you much to play with .,i have went through this on some of my kohlers and found lots of un true areas in the blocks .and had to re machine them .and or lap them true ,on yours its sure looks like heat or lack of lube .or just heat .?i do have some pictures of what i have done ,if you would like to see them .David
 

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just bought a MC 519 cart over the phone from a guy and I want to put it on my 455. from the pics the guy sent me it has the hooks on the front, my question is where does it hook to on the tractor?
The seller bought it with the intention of trying to make it work on a zero turn and never got around to it so he has no answers for me.
I was thinking maybe they hook on to the pins where the 3pt arms are attached to?
thanks
 

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Steve

Deere makes the actual pins to bolt onto the outside of the frame in the back.
I went and made my own set with bolts,nuts,washers,spacers from the hardware store.
The picture is of the bracket on my 322 but my GX345 uses the same pins.Should be the same frame width on your 455.

AJ

 

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Steve,

Here is a better view of that bracket on the hitch plate on my 322 tractor... Like AJ, I made my own shoulder bolt/bushing equivalents from local hardware store items.




And here is an exploded view from the PC 2355 which has all the parts/pieces to your MC519.


Watch your e-mail for some larger files...

Chuck
 

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What Chuck said.

You shouldn't need a bracket for your 455.There should be holes on the outside of the frame like on my GX345.99.999999% certain.

Here is a picture on my GX345,455 frame width should be the same.
Maybe someone who has an MC519 on a 425-455 will chime in for sure.

AJ


 
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