LA140 724 intek V twin rebuild questions.
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    LA140 724 intek V twin rebuild questions.

    I have a 2012 JD LA140 started using a lot of oil. This is one of the ones with the compromised air filter. A few years back I switched out the parts to use the newer style canister filters. I still was seeing dirt inside the housing with a oily coating that had to be coming from the breather from excessive blowby. I did a leakdown test and one cylinder had 10% leakage the other 50%. I took apart the engine and found the 50% leakage cylinder head had a bit of exhaust leak from deposits under the valve. When I removed the pistons the top ring end gap was 3/4 of an inch so that is a classic sigh of dirt ingestion. Here in central texas I mow in a cloud of dirt dust so it is about as extreme a condition as you can get. Anyway the manual says max taper is .003 and that is what I am seeing exceot and the very top where it goes to about .0035 then the very top looks to have a relief on it. Anyway I have a precision hone and I can hone it straight but I would think to get a good cross hatch the top will need to be at a minimum .004. I wanted to go .010 over but all I see is .020 piston/ring sets. I'm thinking I will just hone the bore straight and round and replace the rings. Has anyone done this and did it work out OK? I will need to hone straight then check bore size. Wondering what the max piston skirt to bore clearance is as it is not in the manual just the max bore of 3.120. Thanks for any help on this. I am also going to need to see why dirt appears to get around the cartridge filter.

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    I think you are asking for trouble

    Why not just go with the .020 over piston and rings?

    I think if you bore .005 over you will have piston slap and excess oil consumption then will wonder why you didn't go all the way.
    Last edited by denverguy; 06-15-2018 at 05:51 PM.
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    Run a fine hone in the bad cylinder and look for vertical scratches. If you find any no amount of honing will get rid of them. You will need to bore it out first. Them scratches will cause oil consumption every time.
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    Quote Originally Posted by H-D dealer dude View Post
    Run a fine hone in the bad cylinder and look for vertical scratches. If you find any no amount of honing will get rid of them. You will need to bore it out first. Them scratches will cause oil consumption every time.
    Thanks guys for your feedback, so I just took some more measurements and the taper up to a half an inch of the top is .0022. The big issue is and something I have never see before is what looks liked a machined recess on both cylinders that is .005 larger I can't for the life of me figure out how that happened but I am sure it was not factory and now I will have to go .020 over even though .010 would work. Looks like there are no .010 piston ring sets to be found. Here are some pics of the measurement and the recess. The bore was smooth as glass and if not for this strange top wear I would have been able to hone straight and re-ring. Click image for larger version. 

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    I wouldn't worry about boring it out, but would just hone it and then measure it and see what it is.
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    rebuild progress

    I went ahead and ordered two pistons .020 over. I also ordered some other parts including the valve seals and two intake valves. I reground the valves but one intake has .002 stem wear so I just ordered both. Exhausts have chromed stems and had little wear. I have so far been unsucessfull in getting off the old valve seals. Looks like they press onto the valve guide and are on pretty tight. Click image for larger version. 

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    I started honing and after removing .006 the worn top area is still there, looks like at least .010 till it is gone. Finished cleaning up the heads and am waiting on two new intakes and a 6mm pilot so I can cut the seats. Thinking of milling the heads to give them a better finish to hold the gasket and to insure flatness. Crank looks great and pistons should be here tomorrow. Picture on Amazon shows them with a moly looking coating on the skirts, old ones had no coating. Still wondering why Briggs only sells .020 over pistons and rings. They used to supply .010,.020, .030 years ago.Click image for larger version. 

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    Last edited by ole4; 06-20-2018 at 12:32 PM.

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    did you try simply lapping the valves?
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    no lapping on this one, the valve seating area on the valve was recessed and required grinding, one valve to clean up the seating area wound up with insufficient margin but I did not want to replace just one valve so I ordered both intakes. The exhaust seats actually look OK but the intake seats were not flat. Lapping is fine if seats and valve surfaces still are OK in this case they were not. I also like to cut the seats to make sure they are concentric with the guides.
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    Hmmm, Maybe I'm old school here, but I've never heard of honing a bore round. With time & patience, you can hone a bore straight, but a hone "follows" the out of round bore...and you'll end up with a straight top to bottom egg shaped bore. I'd bore .001 under spec'd size and then hone for size & finish/cross hatch. Bob
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