Export thread

I have a 1997 Craftsman 50" riding mower with a Kohler Command CV25S 25 hp and it's burning oil bad enough to foul one of the plugs in less than an hour of mowing. It has just under 600 hours on the clock. Compression seems really good with just over 180 psi on the affected side and a little over 200 psi on the good side when warmed up. It's burning oil on the side with the breather on the valve cover. The breather doesn't seem to be plugged. I've read here somewhere that the reed valve could be a culprit but I only have side that burns oil. I had to replace a the valve stem seals on one of the heads before at around 100 hours but I don't remember which side. It seemed to have fouled a little differently that time.
I would really appreciate some help to point me in the right direction this time around.
Thanks in advance.

Some of the original CV25 engines had issues with blowing head gaskets. Later models used a head gasket with a fire ring.

I'm sure we can rule out any head gasket problems with my compression test results. Aside the oil burning, it runs really good until the plug fouls. I'm still running the original carburetor but I've replaced both ignition coils this past winter.

Oil rings are responsible for getting excess oil off the cylinder walls. You can have good compression and bad oil rings. That's one possibility.

Another is worn valve guides. They won't be detected with a compression test, either.

The fouling doesn't happen as quickly when I keep the small hose running to the breather disconnected.

So how do you think the oil gets into the combustion chamber ?
The grenlins didn't put it there.
I am sorry there is no can of magic fix sprayed into the air at midnight while dancing naked around your mower.

The compression figures you quoted are garbage the engine does not pack 200 psi brand new.
So you either have a bad head, bad head gasket ( the breather points in this direction ) or bad rings ( only oiling on one cylinder points that way )
One of the 3 or all of the three

Bert, I don't know what to say about the compression numbers but they are what they are. I used a good quality compression gauge and it was done with a warmed up engine. I was a little amazed at the numbers myself. I had used the same gauge on one of my cars recently and the readings I got were normal.

Kohler says that engine should have a minimum of 160 but doesn't give a top number. Just says 160 or above. So your reading may be within the normal range.

Other than the oil burning the engine runs good and still has plenty of power. The biggest issue is I'm poisoning myself when riding the mower, especially at higher RPM's. I can deal with fouling plug easily as it only takes a few minutes to remove, clean and replace it. I'm mowing around 2-1/2 acres about once a week now and spending lots of time in the seat.
I'm not about to buy another mower even though this mower has a lot of other issues but it still cuts grass well.

I'd also be checking for a bad head gasket on that cylinder, but wouldn't rule out a worn oil seal on the intake valve. cylinder leak down test would give you a better picture of what is happening in the cylinder, without tearing anything apart.

I've ordered new valve stem seals for now. I don't have a leak down tester. I've never felt I needed one. Could I have a bad head gasket with a 180 psi?

A few weeks ago I replaced the seals. It seemed to have slightly cured the oil burning problem for a few hours. It was still burning some oil the last time I mowed but not so bad as to foul the plug. Yesterday it was back to burning oil bad enough to foul the right plug to where it started sputtering. I have a feeling there's more than it needing new seals. I'm thinking the head needs rebuilding or even the rings are bad on that side. The tractor itself is pretty worn out. The steering is so sloppy that I'm turning the wheel a 1/4 turn each direction to go straight and the frame has cracks on both sides near where the rear of the engine mounts. I probably need another buy another mower than to waste any more money and time on it. I'm disappointed the engine is needing so much work at just over 600 hours. I'm not buying another machine with a Kohler nor a Craftsman (or whoever builds these things) if I can help it. I just don't what to buy next. I don't want some else's headache and I need something durable to handle mowing around 3 acres of lawn with bumpy terrain.

I'm not a fan of Kohler, Briggs or any other vertical shaft air cooled engine, but don't make a decision when you are pissed. 600 hours doesn't sound like a lot but without knowing the history of those 600 hours, you really can't make a judgment as to whether the oil problem comes from bad design, faulty materials, or failure to perform required maintenance.

At this point, you have nothing to lose by performing a general autopsy (take off the heads) and you just might find the problem is something that's inexpensive and easy to fix. If it is, great. If not, just throw the pieces in a basket and take the whole shebang to the Floral Hills Lawnmower Cemetery (aka, junkyard).

edit: Oops, I see that you've owned it since the 100 hour mark. So you DO know the maintenance history...

Before you spend a lot of time and money on this engine why not try a heavier weight oil?

cpurvis said:

I'm not a fan of Kohler, Briggs or any other vertical shaft air cooled engine, but don't make a decision when you are pissed. 600 hours doesn't sound like a lot but without knowing the history of those 600 hours, you really can't make a judgment as to whether the oil problem comes from bad design, faulty materials, or failure to perform required maintenance.

At this point, you have nothing to lose by performing a general autopsy (take off the heads) and you just might find the problem is something that's inexpensive and easy to fix. If it is, great. If not, just throw the pieces in a basket and take the whole shebang to the Floral Hills Lawnmower Cemetery (aka, junkyard).

edit: Oops, I see that you've owned it since the 100 hour mark. So you DO know the maintenance history...

Click to expand...

I've given it good maintenance so that shouldn't have been an issue. I don't really feel like tearing it down that far as it still runs. I don't want to be without a mower right now. I would if it were at the end of the growing season. I was thinking of using heavier oil like 40wt or adding something like STP.
If the heavier oil helps it enough to just keep the fouling down I'll be able to wait long enough that I might consider tearing in to it but then there's the issue of the worn out steering components. I could always weld the cracks so that's not too big a job.

Oh BTW, I'm not really pissed with it, just disappointed. I'm just faced with the reality that I probably should get something else. I got this thing free when I bought my house nearly 20 years ago. The previous owner probably didn't maintain it right as it was burning oil then at somewhere around 100 hours. I changed the valve stem seals then and they lasted another 400 or so hours. I changed them again, same side and they didn't last very long at all this time around. I have a feeling the valves and/or the guides might be the problem now. The valve stems didn't look damaged but I didn't have them out to mic them or really closely examine them. I could take the head somewhere and have it checked out or rebuilt but I don't know of any shops that work on small engines that I can trust in my area.

If you are going to do a complete overhaul its not cheap unless you have a machine set up in your shop. It sounds to me like you have a 20 + year old mower that's getting worn out. You might find a better used mower cheaper then putting a lot of labor and money into that one. I also find when I get the older mowers into my shop it gets hard to find parts.

I haven't had a problem finding parts after I figured a better way to cross reference the applications. My biggest issue is the down time if I were to tear into this thing majorly. It probably is time to move on. I've been looking to see what's out there. There lots of Craftsmans and Kohler powered machines that I wouldn't consider anymore. There are John Deeres but the prices seem inflated in my area compared to other parts of the state.

Yes it is all about greed & ignorance
Greed = I want everything but I don't want to pay a fair price for it
Ignorance = I have no idea how these things work so I will buy the cheapest so I won't get ripped off.

Thus mowers are made to the cheapest possible price and no one gives a tinkers cures about quality.
Manufactures that take pride in building high quality mowers have all gone broke because people won't pay a fair price for their products.

Most of the repairs I do are from strait out neglect.
I don't check my cars oil every trip so why should I check my mowers oil ?

You may have had a simple problem like a broken oil scraper ring.
However running it like that for so long you will have damaged the bore effectively making the engine scrap.

I used to run a fleet of motorcycles.
They got monthly services, including a compression test.
A loss of compression of 10% was time for new rings.
Plugs did not foul till the compression loss was nearer 50% by which time it was a rebore + pistons & rings.

I will not argue about vertical shaft engines, they are just barely good enough to do the job required.
However so few people would pay the extra for a horizontal shaft engine they have been dropped by all but top shelf commercial models

Bert your advice is spot on. I would pay a fair price for a good piece of equipment if it were offered. For some reason I can't figure, It's hard to find a fair price on anything(not just lawn equipment) used, good or bad, in the Portland metro area. I always find reasonable prices on things outside my usual traveling distance. I never buy big ticket items like vehicles new because I can't afford them. I wouldn't buy a lawn tractor for that same reason. I'm kind of happy I've made this thing last as long as I did. It would have been scrap long ago if I didn't try to take care of it. I was hoping I could keep it going without throwing a lot of money into it. I probably would if the steering wasn't so bad and the frame wasn't cracked in two places.
My understanding is, tractors like I have in that price range, were built better then they were just a few years later. I have a feeling comparably priced mowers, adjusted for inflation, are no better now.

BTW, I check my oil before every mow. If I didn't the engine would have been toast long time ago. It's compression is still more than I would have expected. If it has a broken oil ring I would probably need rebuild the whole engine anyway and I rather just get another mower and be that much ahead. My hydro drive is probably the next thing to go as it gets sluggish after a few hours of running.

Bleach said:

Bert your advice is spot on. I would pay a fair price for a good piece of equipment if it were offered. For some reason I can't figure, It's hard to find a fair price on anything(not just lawn equipment) used, good or bad, in the Portland metro area. I always find reasonable prices on things outside my usual traveling distance. I never buy big ticket items like vehicles new because I can't afford them. I wouldn't buy a lawn tractor for that same reason. I'm kind of happy I've made this thing last as long as I did. It would have been scrap long ago if I didn't try to take care of it. I was hoping I could keep it going without throwing a lot of money into it. I probably would if the steering wasn't so bad and the frame wasn't cracked in two places.
My understanding is, tractors like I have in that price range, were built better then they were just a few years later. I have a feeling comparably priced mowers, adjusted for inflation, are no better now.

BTW, I check my oil before every mow. If I didn't the engine would have been toast long time ago. It's compression is still more than I would have expected. If it has a broken oil ring I would probably need rebuild the whole engine anyway and I rather just get another mower and be that much ahead. My hydro drive is probably the next thing to go as it gets sluggish after a few hours of running.

Click to expand...

Yep.
It has been a good & faithful old horse, but it is time for the knackers yard.
You might just have to bite the bullet and do some long drives.
I have been acquiring 2000 series Cub cadets for a while to resell as these are excellent quality mowers.
Unfortunately they use a unique blade spindle and that was dropped last year.
I bought 10 of them for the time being.
being a tapered roller bearing set up, if the owners remember a couple of shots of grease every season they will last for decades.
The 3000 series are better still having full hydraulics but use a different spindle that is still i production.

Any mower with a drive shaft will be a quality mower.
All hydro drives have a limited service life.
They have a rotating cylinder block with pistons & oil in them spinning on a plate that does not move but has holes in it for the oil to pass through.
Eventually wear between the two kill the unit and there are two of these as the motor is just a pump running backwards.

Generally Garden Tractors ( GT ) will be better than Lawn Tractors ( LT ) as they are built on stronger frames to allow earth working attachments to be fitted.

Beware of Eaton drives.
While Eaton were one of the best in the business, for the same reason as the previous post, they no longer make , service or supply parts for mower drives & pumps.
Some mowers have compact tractor Eatons that are current but most run the garden line which has been deleted.

As for your mower, now I have a full picture, some "No Smoke" in the oil and if necessary a longer exhaust blowing out the back might get you through a few more seasons.

Sound advice Bert. My thoughts exactly. I've pondered the idea of a longer exhaust. I'll have to do that for sure. I smell like burned exhaust after mowing a short time.

Bleach said:

Sound advice Bert. My thoughts exactly. I've pondered the idea of a longer exhaust. I'll have to do that for sure. I smell like burned exhaust after mowing a short time.

Click to expand...

2' of flex tube should work fine.
when it gets really bad, mow in the evening when no one will notice and wear a boiler suit so you don't end up smelling like a submariner ( sorry Roger ) when you are finished.
Switching to a heavier based synthetic oil or even Harley oil 50W 70 might buy you some more time.

I was trying to figure what to use for an exhaust pipe. That sounds like a great idea Bert. I do plan on starting with maybe 40w or 50w oil. It too hard to get the really thick oil additives down that skinny oil fill tube.
It's hard to mow in the later hours. It's hard to get mow lines straight and I miss where I need to mow :wink:

Bleach said:

I was trying to figure what to use for an exhaust pipe. That sounds like a great idea Bert. I do plan on starting with maybe 40w or 50w oil. It too hard to get the really thick oil additives down that skinny oil fill tube.
It's hard to mow in the later hours. It's hard to get mow lines straight and I miss where I need to mow :wink:

Click to expand...

Should find some at truck supplies or some speed shops.

Thanks. I'm glad you told me where to find flex pipe. I would have tried looking at a home improvement store.:ashamed:

Bleach said:

Thanks. I'm glad you told me where to find flex pipe. I would have tried looking at a home improvement store.:ashamed:

Click to expand...

You would have better luck finding the flex pipe in a auto parts store like NAPA or Pep boys.

Today I decided to pull the #1 cylinder head that was the side that was burning oil. There was some oil in the cylinder but the cylinder bore was still in great shape. The crosshatching was still visible. It looks like maybe one or both of the valves and or guides are bad. I could hear hissing coming from the valve areas when I turned the engine by hand before I pulled the head with the valve cover off. I couldn't hear anything like that on #2.
I'm going to get the head rebuilt or just buy a new head. Does anyone have any suggestions who could rebuild the head or a good source for the head with valves? Ebay has them from various sellers from $117 to $145 for just a bare head. There's a seller who listed a complete rebuilt head for $150 shipped with perfect feedback. I'm not sure what the going rate is anymore for rebuilding heads. The last time I had a head rebuilt was for a car and it didn't even cost $150. It's been a very long time.

Bleach said:

Today I decided to pull the #1 cylinder head that was the side that was burning oil. There was some oil in the cylinder but the cylinder bore was still in great shape. The crosshatching was still visible. It looks like maybe one or both of the valves and or guides are bad. I could hear hissing coming from the valve areas when I turned the engine by hand before I pulled the head with the valve cover off. I couldn't hear anything like that on #2.
I'm going to get the head rebuilt or just buy a new head. Does anyone have any suggestions who could rebuild the head or a good source for the head with valves? Ebay has them from various sellers from $117 to $145 for just a bare head. There's a seller who listed a complete rebuilt head for $150 shipped with perfect feedback. I'm not sure what the going rate is anymore for rebuilding heads. The last time I had a head rebuilt was for a car and it didn't even cost $150. It's been a very long time.

Click to expand...

Welcome to the real world of rebuilding a engine. It wouldn't be any cheaper to take the head to a machine shop. Maybe you can find a good used head? 150 dollars for a (GOOD?) rebuild head doesn't sound that bad to me and then also you will need a gasket set on top of that. If that dose fix your problem you will be ahead on this for small dollars.

I've searched around a bit more and I found another head for less than a $100. I'm in contact with the seller to get more details about the rebuild.
I'm sure another good head will take care the issue. There weren't any signs of damage to the bore.

I got more info about the head that I found for under $100. The seller informed me that it was a good head that had been cleaned and the valves and seats were resurfaced. I saw similar carbon staining around the exhaust valve guide on the top of the head. I think I'll just bite the bullet and buy a new head, get new valves and seals. I'm sure I can reuse the valve springs and retainers.

I researched the Husky and it seems to be a little bit light in construction, i.e. light gauge steel, etc. I have areas of rough terrain and I also have a habit of getting very close to stumps, trees, posts and walls. I think I would end up breaking things fairly easily. That's why I decided to bite the bullet and tear into my old machine and give it another chance.

Just curious, why are you changing the head for oil burning? Worn intake valve stems and guides because that will be the cause of oil consumption. Just how loose are they? The intake wear limit is 0.2809 and the exhaust wear limit is 0.2819. Myself I would check this before investing in new heads.

I can get side to side play with the valves inserted in the guides. I have no way to measure the guides ID but the valves were still within spec but the exhaust valve stem did have visible wear. I did find a machine shop that might be able to rework the old head. If not. I'll probably end up buying a new head.
The problem with these heads are that the guides are not replaceable and have limits on knurling them and then you have to buy valves with oversized stems.

Bleach said:

I can get side to side play with the valves inserted in the guides. I have no way to measure the guides ID but the valves were still within spec but the exhaust valve stem did have visible wear. I did find a machine shop that might be able to rework the old head. If not. I'll probably end up buying a new head.
The problem with these heads are that the guides are not replaceable and have limits on knurling them and then you have to buy valves with oversized stems.

Click to expand...

I would be surprised if Kohler didn't make oversize valve guide bushings.

I just did this on a very old 3 hp Briggs engine. The bushings are very cheap and it cost $25 to get them installed by a machine shop. The bushings have the correct ID and the head (or block in my case) is bored or reamed to the correct diameter for a light press fit.

I got the head back yesterday and got it all back together today. It all started fine and idled good for a few minutes but when I increased the rpm's it all of the sudden went wide open throttle and I couldn't get it slow down. I had to choke it to slow it down. I checked the governor linkage and I have it set correctly. The carb throttle keeps opening up if I don't hold the linkage. If I take the small spring off the throttle link and lever it will idle normally but will surge if I increase the rpms. I've tried different holes on the governor lever and it goes WOT every time if I keep the spring attached to the throttle link and lever. For whatever reason the spring keeps it from closing. I'm thinking something might have happened to the governor.
In the meantime my grass keeps growing.

I was reading around the site and came across a thread where some mentioned a clock spring on the carb on a different engine. This could solve my throttle problem but I didn't see any clock spring on my carb. I need to try to find one that would fit. I'm sure one would have enough tension to keep the throttle from opening up on its own.

It runs fine now and doesn't seem to burn oil like before but something in the transmission may have quit.

Bleach said:

I have a 1997 Craftsman 50" riding mower with a Kohler Command CV25S 25 hp and it's burning oil bad enough to foul one of the plugs in less than an hour of mowing. It has just under 600 hours on the clock. Compression seems really good with just over 180 psi on the affected side and a little over 200 psi on the good side when warmed up. It's burning oil on the side with the breather on the valve cover. The breather doesn't seem to be plugged. I've read here somewhere that the reed valve could be a culprit but I only have side that burns oil. I had to replace a the valve stem seals on one of the heads before at around 100 hours but I don't remember which side. It seemed to have fouled a little differently that time.
I would really appreciate some help to point me in the right direction this time around.
Thanks in advance.

Click to expand...

Bleach, I just acquired a 25 hp Kohler from my neighbor. He said it was smoking bad + leaking oil from the oil pan. Upon tear down, I sure didn't see any evidence of broken rings, in fact rings looked real good as well as the cylinders. I sure see it was burning oil as the number 2 combustion chamber was heavily fouled with carbon. So I would suspect breather issues and or worn valve seals. I'm in the process of rebuilding this engine and both my neighbor and I will have a spare. I too have a 25hp Kohler and run the crap out of my Craftsman in the summer. Mine smokes a bit on start up, and is 17 years old but is a good runner overall. The neighbors engine had some issues, where the crank gear had chewed into the oil pan thrust surface. I'm in the process of machining down the thrust surface .125 and then add a .125 washer and just a little bigger around to spread out thrust. The crank gear which has the thrust bearing surface is ( in my opinion) small?? Kohler says this is not an issue. Will update this overhaul when I'm finished.

I've seen this problem several times on the 25hp Kohler Command Pro. The way I solved the oil burning problem is I replaced the piston rings with a new ring set that included an improved type 2 piece oil control ring. The stock 3 piece oil ring loses tension and the rails (the very thing upper & lower oil rings) stick to the expander. Therefore, the stock oil control rings become ineffective and you burn lots of oil. The ring set with the improved 2 piece oil rings is available on eBay & other sites - it replaces oem p/n 2410814S. You'll see the 2 piece oil ring design used on many high end engines that need the ring set to last a long time. They are used in Cummins, Detroit Diesel & Caterpillar diesels. They are more expensive to manufacture than the 3 piece design & the last a lot longer and don't lose tension. I've used the 2 piece oil rings in 4 of our Kohlers and oil consumption is virtually nil.