Oil Soaked Plugs

[White Oak Dave]

Hello,
I have been working on a Kohler Command Pro CV23S 23 HP twin cylinder in a L130 John Deere. I got the tractor for free because the previous owner blew one of the rods but did not appear to hurt the case or the cam. I replaced the crank, rods, rings, coils and head gaskets. It fired right up but after several minutes it started to stumble under load and blow some blue/white smoke. It now smokes when you start it for several seconds, as if to clear oil that is built up in the cylinder and still stumbles on acceleration. Both spark plugs (new) are wet with oil. I mic-ed the bore and pistons and they are well within tolerance and the end gaps are good on the rings. I also have a 150lbs of compression on both cylinders.
The last thing I have ordered to replace is the seals for the intake valves in the event they are sucking oil in.
Does anyone have another suggestion for the source of the oil in the cylinders before I button this up again and try it? Any advice is appreciated.
Thanks,
Dave

 

[sgkent]

Assume you cross hatched the bore for the new rings?

 

[hlw49]

Might check the crank case reed valves. There is one on each cylinder between the lifters.

 

[White Oak Dave]

Good morning, I did cross hatch the bore, but not sure if I was aggressive enough. It appeared the walls were almost smooth again after the hour of running that I did before tear down again.

As for the reeds, they are in place and laying flat in each lifter bore. I could not find a test or specs for them but did pull each out and ensure they we intact.

Thanks for the quick response.

 

[StarTech]

Did you check the cylinder at twice at three levels (top, middle, and bottom of the piston stroke) and at 90 degrees of each mic check? Otherwords mic'd the cylinder in six places. This done to check for both ovaling and tapering. On top honing should be done with a rigid hone as a flex hone can just make things worst.

 

[White Oak Dave]

Thanks! Yes, I did check top middle and bottom and side to side. All are very close to the 3.149. I will look into the rigid hone. It would be a good addition to the shop. Mine is the flex one that goes in a drill motor and the stones are worn.
Since you folks are so helpful.... I can't seem to get an accurate reading on the valve guides. The ball gauge I have is showing tighter than the stems and the valve stems are right on the money. They seem fine, not sloppy or anything in the guides.
Also, the piston itself is tapered? It only says to measure .25 from the bottom on the skirt and nothing about the top measurement. I am showing a uniform taper of about .017 on both and have read that aluminum pistons are tapered for heat expansion at the top. Just confirming, because both pistons have a slight back and forwards rock to them but not parallel to the wrist pin.

 

[sgkent]

clean the valves, oil the stem and put it in a guide sitting up about 1/2". Wiggle the head. If it is tight then they are Ok, if it is sloppy then they are worn. If it rattles around they are really worn. When a guide is replaced on any motor the hole will be slightly different than before so pay close attention when lapping to be sure that the whole seat is contacting and not just one side. There will be a bit of play but it should not be loose side to side. Example, new would be a rock of maybe .003: to .004" but if the valve head say rocked .005" or .006" side to side I would consider that worn but workable. If it rocks .020" to .040" side to side it is really worn.

Pistons are usually wider on the bottom or the sside just above the wrist pins. If the skirts taper in they are collapsed and will rattle a little. If the skirt has a tang on it so part of the skirt is cut away, and they are collapsed you can use a rawhide mallet to gently tap them back out a bit to the same as just above the wrist pin. Check the ring lands to be sure they aren't worn out.

All my training comes from being an automotive machinist but small engines should be similar.

 

[White Oak Dave]

Great advice on the valves. I will try that tomorrow. I should get my new hone from Amazon as well. Thanks to everyone for all the great help. My first time on a forum, this one is awesome.
I post back my results.

 

[White Oak Dave]

clean the valves, oil the stem and put it in a guide sitting up about 1/2". Wiggle the head. If it is tight then they are Ok, if it is sloppy then they are worn. If it rattles around they are really worn. When a guide is replaced on any motor the hole will be slightly different than before so pay close attention when lapping to be sure that the whole seat is contacting and not just one side. There will be a bit of play but it should not be loose side to side. Example, new would be a rock of maybe .003: to .004" but if the valve head say rocked .005" or .006" side to side I would consider that worn but workable. If it rocks .020" to .040" side to side it is really worn.

Pistons are usually wider on the bottom or the sside just above the wrist pins. If the skirts taper in they are collapsed and will rattle a little. If the skirt has a tang on it so part of the skirt is cut away, and they are collapsed you can use a rawhide mallet to gently tap them back out a bit to the same as just above the wrist pin. Check the ring lands to be sure they aren't worn out.

All my training comes from being an automotive machinist but small engines should be similar.

Great advice on the valves and there is very little side to side movement.

Quick question about honing. I received a new hone today with 4" 220 grit stones. I plan to hone this weekend. Is is okay to use the new rings that I ran in the engine for 30 minutes or so when the honing was not done well enough? Have I ruined them? They are still well within spec as far as the end gaps.

 

[sgkent]

I think you will be ok. try to get the crosshatch lines at 45 degrees to one another. You do so by controlling the speed. The stones should go about 1/3 past the end of the cylinder on both sides. Maybe 3 or 4 passes, then check it. If that looks even, stop.