I have a Kohler MV16 Twin Cylinder Engine on my bench (1979 1300 hours)
that is using an excessive amount of oil. (lots of oil smoke out the muffler when running.) I have both heads off, trying to assess what is required to bring it back to normal operation. I have owned this mower since new, and it has never been bored, only one valve job four years ago. The cylinder bore is smooth, no scoring, and within specifications. (It should not need to be resleeved like my last one) There is a LOT of play between the piston, rings and bore. I do not have enough experience to determine how far to go with this. New standard rings, new oversize rings, use old pistons, buy new bigger pistions or what.

The last one was easy, I had the bore resleeved to original bore diameter and put in a new standard piston with rings. I don't know what to measure to determine what to do with this one.

 

You said the bore was "within specifications". If you know the specifications and are able to measure the bore it should be easy to know what you need to do. If you were just guessing that the bore was good then that's another story especially since you mentioned that there is a lot of play between the piston and cylinder.

What are the measurements of your cylinder? top, middle and bottom and is it the same at each when you measure 90 degrees (X and Y)? What are the measurements for your piston?

 

In my experience, measuring the bore accurately is very tricky, as Pilot mentioned. I'm not familiar with that particular engine, but I would want accurate measurements of everything he mentions, which will enable you to figure taper and out of round, which can be significant. I'd take it to a machine shop who does lots of small engine work. They know what to look for and have the tools to take accurate measurements. Good luck- Steve

 

If the bore is within specs and there is little to no ridge at the top of the cylinder, I would check the pistons and see how much wear they have, especially down low on the skirts. If they have a lot, put new ones in and check your ring end gaps. If the bore is in specs, then new standard rings will be fine but check the gaps anyway to avoid problems. The cylinders MUST be honed with a good cross-hatch pattern to stop the smoking problem and allow the rings and cylinder surfaces to seat in propelry. I'd be paying attention to the rod clearance too, if it has that much age and wear on it, it would probably be a good idea to put new ones in. You don't want to have a rod break 6 months after doing all this other work.

 

My local small engine guru measured everything for me today, and we determined that all the bore needs is to be re honed. I will get new pistons and rods, rings, valve guides etc just to be safe. I did something stupid in the transportation back from his shop and snapped off the oil dipstick fill tube right at the base where it inserted into the crankcase. Now I need a trick to get out the piece that is stuck in the crankcase before I have to call the guy who just got me going and tell him what an idiot I was. Any ideas here?

 

There are extractor tools. They are made for removing broken off bolts or pipe fittings.



You can also try inserting a drill bit one size larger than the inside of the dipstick tube. Turn the bit just enough for it to bite into the tube and hopefully you can spin and pull it free. You can also chisel the tube out if you are careful. And lastly you can drive it out with a punch and hammer from the inside of the case.

 

Thank you for the photo and the reply. The filler tube is about an inch in diameter, and I do not have any drill bits or extractors that large. I am going to try to make something that will do the job. Does anyone know whether Kohler used some type of adhesive when they inserted this tube into the crankcase? I was thinking that using some low controlled heat might loosen it up.

 

On both of my Kohlers (a 14HP & a 25HP Command Pro) the oil fill tube is just a press fit into the crankcase hole with an o-ring around it. It should pull right out if you can grab it with needle nose pliers, or you might be able to fashion a hook out of baling wire & grab the lower lip from the inside & pull it up and out.
Please provide the model & serial numbers of your engine, I have all of the Kohler manuals and might be able to look it up.
As for your burning oil, I bought a head and valves for my 25HP Command Pro (on a mechanics suggestion), and as it turned out all it needed was a pair of $3 oil seals on the valves. You have to pull the head & valves to replace them but it wasn't all that difficult. I rented / borrowed a valve spring compressor at the parts house. I ended up spending almost 200 bucks and really only needed a pair of $3 valve seals. I've been running that mower for 8 years since that repair & it doesn't burn a drop of oil.

TexasFire

 

I made a puller to remove the fill tube without more damage. The cylinder jugs are in the machine shop getting honed, new guides, valve job and seals. I'm just waiting for them to call so I can start reassembly.

Thanks for the reply!

 

I would have suggested just using a 'glaze breaker' when installing the new pistons & rings. If there were no scoring marks, a glaze breaker would help the new rings to seat. I would also have checked amount of wobble in the guides before replacing, holding the valve 1/4" off the seat and moving it around. It should have a bit of wobble, but not much when that close to being closed.
Be sure to torque the head bolts in steps of ~1/3 total value and in sequence. A 1/4" drive torque wrench is almost mandatory for small engine work.
tom

 

I got the cylinder jugs back yesterday, and am installing the pistons. Cheese suggested checking the ring end gaps but my Kohler Service manual does not have any specs for those. The rings compressed ok with the compressor to install the first one in the cylinder. This is the first time I went this far with a repair so I am not sure how snug everything should be. The piston requires some serious pressure to move it up and down, but it does move. Does anyone have end gap specs for a Kohler MV16S Model 56511 and if anyone has done a rebuild to this level, comments would be appreciated as to how tight the pistons should be in the cylinders.

Thanks!

 

Looks like the ring gap would be .010 - .023 for new rings which I assume you're putting in or for additional info used rings would have a max gap of .032.

As for how much pressure to move a new piston which has been lubed with light oil, it shouldn't take much, but if your piston is matched to either a standard size or whatever oversize the machine work took it to and the ring gap of the correct set of piston/rings is right then you should be OK.

For instance, you overbored to .020 and the piston and rings are oversized to .020 and the ring gap is .010 - .023 then everything should be OK and the piston will loosen up with use.

However, make sure everything matches the specs or the piston could seize up when it heats a little.

 

Oil the cylinder up good while you assemble.
As long as the piston fit loosely in the cylinder WITHOUT the rings, and the rings DO have an end gap. You should be fine. You will be surprised once you get the rod on the crank and turn it with the crank how much different it will feel.
I don't have any numbers for ya without looking, but I would say least .015-.025.

 

marbobj beat me to the numbers

Personally I would rather be on the high end of the spec rather than the low end. As everything heats up and expands, that gap will close, you need to make sure there is enough gap cold that it never closes completely when hot.

Sounds like you have a good "german" fit....Neizentite!!!

 

I'm putting new rings on the original pistons, (basically fell out of the engine when we took the jugs off. I can check the gap on the next one and that will tell me if I have to take the other one back out.

Thanks for the numbers!

 

Were the cylinders just honed at the machine shop and were they checked for taper specs?

 

Well that may not be accurate because each cylinder may have worn to a different bore.
IOW, did you mic the cylinders? It can happen that you can have one set of rings that fit one cylinder with .012 end gap, the other cylinder same rings have .022 end gap. The next set of rings could be vice versa.

 

As far as measuring taper, it should not be a big deal since you are using the original pistons.
However, you could still measure it by measuring the end gap of the ring at the top of the cylinder and again at the bottom.

 

I read you loud and clear on the wrong assumption on my part. I will be taking the other piston back out to re check the gap as well.(The cylinder bores were just re cross hatched) I found the page in the engine manual that deals with ring gap and it said to use .010 to .032 for a used cylinder bore. One thing was very unclear about installing the Oil control ring. It says to make sure the ends fof the expanders don't overlap, and I get that, but what about the the two rings that go over and under the expanders? Can they be lined up with the expanders, should they be lined up with the expanders, or should they be lined up in another position on the piston?

 

Offset the two oil rings 90 degrees either way to the break in the expander. Use that for positioning all the rings on the piston. None of the ring gaps should align with the next ring down.

If all that has been done with the cylinders is honing them and you don't plan on doing anything else, I would just check the ring gap with the compression ring down about an inch from the top of the cylinder, then again a couple inches up from the bottom of the cylinder, just to see how close you are to the allowable ring gap specs.

When you check the bottom of the cylinder see if you can see light between the ring and the cylinder wall. That's on the two sides that fall on a perpendicular line to the crank. That will give you an idea of how oblong the cylinder is at the bottom.

When you check a cylinder for a ring gap only put the ring in the cylinder, no piston. Then position the ring equal distance from the top/bottom of the cylinder.

Unless you plan on going to the expense of boring with new pistons and rings, I wouldn't take the other side apart. If the gap is way out of specs you may have to rethink the project.

 

10-4 on the oil ring off set, will move them now. The rings were uniformly, (top and bottom measurement) too close together so I opened them up a bit to specification, High side per Cheese suggestion. T!hanks for the help and suggestions!

 

I like to see ring end gaps between .010 and .025 to feel good about how well the rebuild is going to "take" and the longevity of it. Stagger all the ring gaps, make sure you get the rings right side up and in the proper order, oil the rings and piston well before installing, oil the rod journals before putting the rods on, oil everything prior to assembly. I like to use vaseline on the rod journals and other bearing surfaces. It stays in place well and as soon as it cranks up and warms, it melts into the oil. White lube works well too.

 

10-4 on the oiling everything, and the Vaseline trick for the Rod Journals. I purchased a tube of GE Silicone RTV (suggested in the service manual) but there was no suggestion on the package or in the manual as to what to best clean the old RTV off the crankcase. I thought I could use brake parts cleaner but you might have a better Idea?

 

That or aerosol carb cleaner. Spray it, let it sit ten minutes, then repeat.

 

The combination oft the two along with some serious scraping with a rubber bondo applicator worked. I would have imagined that some chemical whiz would have something that would work faster, but this will work for now.

Thanks for the tip!

 

I have everything lined up and the barrels are clean and ready to be fastened to the crankcase. These barrels require an initial torque setting per the sequence in the manual of 100 inch pounds. I have a torque wrench, but getting the sockets and extensions around the cooling fins is impossible with the tools I have. Do you recommend some type of lateral torque wrench or do you guys just wing it with conventional wrenches?

 

They make wrenches you can put on a ratchet:

S-K Offers New 3/8" and 1/2" Drive Crowfoot Open End Wrench Sets

The additional length changes your torque, so you'll want to calibrate by torquing a bolt and finding the torque to break it back loose, then see how much different it is with the wrench adapter on the same bolt, then use that information to adjust the torque setting on the wrench for the hard-to-get-to bolts.

 

Back in the Mower, wasn't sure about the electric clutch surviving the beating it took to get it off the crankshaft so I could even get the engine out. It rocks! Engine hit on the first go around and has mowed a couple of lawns and runs and sounds great! Thanks for all the replies and great advice!

WML 13

 

Great! I love it when a plan comes together! (said in my best John "Hannibal" Smith voice )