Anti-smoking (engine) campaign: 1450
 

Finally have the time to pull the engine from my 1450 to diagnose the excessive oil consumption. Here are some pics. Haven't mic'd the cylinder yet, but there is quite a gap between the piston and the cylinder wall at the bottom of the stroke on the valve/carb side of the cylinder. Several of the head bolts were pretty loose, too, so it's definitely time for some work.

The cylinder is not scored anywhere that I can see, but there is a lot of oil on top of the piston, and this is just from running it up from the storage building up to the workshop, a couple hundred yards. I think it's just the piston that is worn. It was burning 8-12 oz per hour--in other words I was was adding a pint every time I cut the grass! Talk about a smoke screen!

I found a machine shop in town (NAPA shop/Richmond) that can machine the block. So I've got to tear it down to the bare block, and that will be a new experience for me. I've replaced a piston before, but never totally stripped a block. I may be posting some questions as I make some progress on this. I'll post the results of my cylinder measurements once I get the piston out.

I'd be interested in any tips/tricks that you guys can recommend for things to definitely look out for or change as I reassemble. I'll buy a rebuild kit off ebay once I find out the proper piston size (if it needs to be bored). If it has balance gears, I'll remove them, but not sure these engines even have them. I'll see when I get the oil pan off. What upgrades would you recommend?


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Well, you are one step ahead of me! At least it looks like all your head bolts came out w/o busting any! I just did a 14HP last spring. The machine shop (NAPA) and parts bill total was $233 and they had to remove 1 broken bolt.

Inspect your oil pan closely for stripped threads, cracks and worn mounting pads. I had mine milled flat and added flat washers to get it back up to where it belongs. This would be a great time to upgrade to a cast iron pan if yours happens to be in bad shape.

Have your shop check for proper cam shimming and run-out. I have been told that is the source for the "Kohler Knock" which I have in mine as well as a 1250 that is next in line for re-hab. Keep us posted!! and good luck!

judging by the wear that I can see in the bore it'll need to go .010 os

You may be right, but the pictures can be deceiving--the cylinder walls are like a mirror and there are lots of reflections in the pictures that look like defects in the cylinder walls that are not there. I haven't measured it yet, so it may be out of round or otherwise worn, but it's not scored or damaged.

I agree with Don. It's not that we can see defects... It's the fact that it is that shiny along with the absence of the crosshatch. A cylinder wall isn't supposed to be reflective like a mirror. The way the carbon trail goes from the cylinder to the valves indicates it is burning oil. The color of the valves indicates that it had low cylinder temperatures, caused either from a rich carb setting or from low compression. From the look of the cylinder, I'm saying slightly low compression. From the look of the top of the piston, when you get it out, I think you will find, that compression was going past the top ring and on into the second. It will be black between the top and second ring. I also think you will find the bore to be a little egg shaped.

I got the engine dis-assembled tonight, and mic'd the bore at 3.502 to 3.503, so it's at the wear limit. Very light scoring (can't feel with fingernail, but visible with a raking light). Somewhat egg shaped.

The piston is very interesting. See pics. How does the top edge of the piston get damaged like?

The block's going to the machine shop tomorrow.

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Well, I wondered about the piston being scored like that.... but couldn't tell if it was just an anomaly in your earlier pics, or if it was really there.

The piston damage, was caused by compression/hot combustion gas going past the rings. Severe blow by. What happens is, after ignition, the hot air/ or the flame-front actually goes between the piston rings and the cylinder wall. That causes the edge of the piston to get very, very hot. Then it just erodes it away like a blow torch. That erosion was on the valve side of the piston because that is where the plug is and ignition starts. It was running a little rich, and I'd say just a little out of time. Lugging usually plays a role in this type of damage also.

From these recent pics, we can also see, that not only was the first ring not sealing, neither was the second. (It's not really designed to, and won't handle doing the first rings job for very long.) The piston skirt is dark brown/black from the leaking compression and oil being "cooked" on it from the heat.

Couple of things I'd check, (this is from what I see in the pics):
*Rod journal on the crank is probably egg shaped on the "power" side. I hope you had planned to grind it.
*In one pic the cam looks blue near the exhaust lobe. May have gotten hot. Look it over good, and mic it.

I'd like to see some pics of:
The bore now that the piston is out
The valves
The valve seats
The connecting rod journal end with the cap off
A shot of the piston looking at it from the side where the erosion is.

Looks like there is some damage to the skirt on the side of the erosion. May just be wear, but it looks like it had some pretty good "piston slap". I will say, that motor was close to scoring the piston and locking up. Probably didn't just because the piston was so loose in the bore.

Thanks, JMech, let me know what you think. I don't have a good mic to check the rod journal, so I'll let the shop check that. The lobes on the cam look OK to me, not sure what that discolored spot is from, maybe original grinding? Here are the requested pics.


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The wear on the top part of the piston is normal for a hi hour Kohler engine. Most Kohlers I rebuild have some of the scoring around the exhaust valve area on the piston.

Wow, you got the good out of that motor!

The valves and seats are shot. The machine shop shouldn't have any problem replacing the seats. Get new valve guides too. With that much wear, I wouldn't even check them, I'd just replace. The cylinder will clean up nicely. I bet it takes at least .020 though. .010 might get it.... but I doubt it. It has been warm. Not necessarily overheated, just been a little hot. Side view of the piston looks like it should. What I thought I saw in the other pic isn't there in this pic. Rod wore good, just like it is supposed to. The machine shop will check the journal, but I'm sure it will be out of round. Cam is fine. Might clean it up good and post another pic, but I don't really see anything scary. Just for good measure, have the shop check the deck on the block and make sure it is good and flat. I'm sure it is, but I usually double check it to be sure, especially on a motor that has that much wear. You have got to be happy, that motor worked hard and lasted a long time! Do this rebuild right (which you are) and it will last you another 40 years! Good job so far! :ThumbsUp:

I dropped the block and crank off at the machine shop. He said he needs the valves to do the seats and guides. So I'll have to order them and take them over there. He said the guides seldom wear, but he'll do what ever I want him to do. Help me out here--$334 for two valves, two guides, two seats and two springs? Partstree.com. What's another source? The master rebuild kits on ebay are $110 and include the valves, but not the seats or guides.

I'm in the middle of a 12HP rebuild. I'm ready to order the kit. I'm getting an E-Bay one. I'm just going to have my shop supply the valve seats. I have no problem with non-OEM parts. Here's the kit I'm getting.... E-Bay They have the guides listed separately for $17.50.

That's the same kit I was looking at (for the 14 hp of course). Once they bore the cylinder he's supposed to call me with the result (Friday?), and I'll order the kit and take him the valves. I'll ask him if he can get the seats. If not, I'll order them too. Do you routinely replace valve springs? Any reason to do that?

I appreciate your help, Jonathan.

-Frank

It probably wouldn't hurt to replace the springs I'm sure they have lost a little of their strength over the years

Not necessary to replace the valve springs unless you really want to. In my opinion. A good three angle valve grind is more important.

On a lot of the other engines I rebuild, I have in recent years been replacing valve springs. But that is only because the engine company I use started offering a kit that included all valve components and they made the price very worthwhile. As far as the Kohlers go, no, unless they are damaged, or been hot, I just use them over. Replacing them is up to you. They are about $12 a piece. No, I don't routinely replace them. If you do decide to replace, save the old. You may have one on another engine break and need one. :beerchug:

Godd job SDD, I'm doing another 301 as we speak and internals look identical to yours as far as the roached piston and oil consumption, smoke. Your exhaust seat has seen its better days, thanks for sharing the close ups. I'm thinking mine will have to go .020" over on the bore as well by that's to be expected. I'd like to know, if you dont mind, what you're machine shop charges itemized so I can gauge mine since he hasn't told me what it's going to be yet, but boring is going to happen for sure. Keep us posted and hope you "stop smoking" after this. My 123 is trying to quit too, lol

unless the seat shows damage I don't replace them. I just grind the seats. even if you replace them you still need to grind the new seats so they are eccentric to the guide.
but to echo what the others say this engine lived allot of years so if its rebuilt properly there's no reason you can't get just as many back out of it if cared for properly.

Don, have you ever had trouble with them getting too low? I wasn't sure if they would be able to face them enough without the valve getting too low. They look pretty low. :bigthink: Or do you just face the stem off in that situation?

only time I've run into it is if its had several valve jobs or the seat is really messed up. the majority of the time a couple taps with the seat grinder is all it takes to bring them back. I then use a 15 deg. stone to move the interference point to where it comes out in the middle of the seat on the valve. you already know but for others the closer the interference point is to the edge of the valve the greater the chance of burning the valve . when I refer to interference point if you grind the seat to a 45 deg angle you then come back with a 15 deg stone and the point that the 45 and the 15 meet is the interference point. when you install the valve and check where the interference point meet on the valve face you want it to be near the center of the face. you can use grease or bluing to check this or simply use a little lapping compound. if you want a 3 angle then you add a 60 deg, 70 deg or whatever you think will work best below the 45. so as an example you could use 80 - 45 - 15 . that's not what I would use but I'm not about to say what I would use.
but, back to the original question. you also measure from the fire deck to the top of the valve to make sure the valve is not dropping to far in. if it is then a new seat would be required. the only things that I could really think of that would be affected would be valve spring seat tension and possibly some flow. from what I can remember I don't believe Kohler has a spec for that on the flat heads.

When I used to work at a lawnmower shop, we used a Neway valve seat cutter. They are pricey ($350+). Not for a one-time use, but they are nice.
Hand operated. We had 3 or 4 different angles to get the contact just right. You can google it to check it out. Might find a small engine shop that has one you could use.

Thanks for the education on valve seats. I had no idea. This is why this place is so great! Now i can speak intelligently to the machine shop. They do a lot of Kohlers, he saw it coming and knew exactly what it was. So I'll ask his advice on the seats and guides. I hope to find out tomorrow what the results of the cylinder bore were and how the crank fared.

Good post on details of engine rebuild. The shop I used last for the 14 hp wanted the over sized new piston in hand prior to doing bore work. Second I suggested he change the valve guides and he said that they did not need it. I followed his lead. Always is rewarding to hear one of these fire up after a rebuild. Good luck and keep us posted.
Regards,
Chris

The shop called, said the cylinder will go 0.010 over and the crank was ground 0.010 under. The cylinder was 3-4 mils out of round and the crank was 0.0015 below the min. He said the seats just needed to be ground, not replaced.

I ordered the master rebuild kit off ebay, and will take him the valves when they come in so he can finish it up.

All good news! Sounds like you have a good machine shop!
:IH Trusted Hand:

I agree! Thanks for the update.

And guess what? The result was EXACTLY what you said it would be, Jonathan.

It's my first experience with this shop, but it's the "go to" shop for Richmond, VA and others have said they do good work. The machinist called when he said he would, that's a good sign.

I prefer to have the piston in hand also. while you can bore to .010 and just measure it . I guess in a world of + and - ranges for manufacturing I still like to put the piston in the bore and check the side clearance with a long feeler gauge . I've just seen to many rebuild go bad by assuming

I agree with this, my race engine shop would not bore my block until he had the pistons for it. I'd get the new parts and then hand the shop the parts and the block.

The shop I currently use, and the one I used before they closed, both would take my blocks and bore them to just under a size. Like .0075, or .018, that way we would know how much it needed, then order the piston, and finish the bore. That way, they could still cut and fit. I preferred this because, before, we might think .010 would get it, and it wouldn't. I agree, piston in hand before the bore is finished, and I ALWAYS check skirt clearance. Even if my shop tells me it's good. I usually double check my crankshaft journals too. Only had 1 crank that had a mistake, but it would have cost the motor had I not caught it.

I'm not sure he bored the cylinder yet--he told me it would it was 3-4 mils out of round and would go .010 over. Had planned to take him the piston, rod and valves when they get here early next week.

Identical story to mine SDD. I stopped by the machine shop today and watched him mic mine, same story, .010 over will get it and surprised by that because of the middle of the cylinder having metal rusted away and missing. He also said he needed the piston which judging from the rest of these posts is a good thing. So I'm assuming you ordered a kit with a ten over piston and ten under rod? I did that on my last one. And the eBay kit worked well, ring instructions were very misleading and vague for someone like me that doesn't do engines all the time but other than that everything was good. Question, how many gasket shims did you have behind your bearing plate? This is my second that had two and was just wondering about yours and others. Its the ones that control end play.

Yes, I ordered the .010 over piston and .010 under rod kit. I saved a piece of the bearing plate shims so I can reproduce the same thickness (maybe). I didn't pull them apart to verify exactly, but it looked like two shims.

Took the piston, rod and valves to the machine shop yesterday. They called today to say the engine was ready, so I'll pick it up tomorrow. They had bored the cylinder already, he said they usually do that, the new pistons are predictable in size, so he's never had a problem with clearances. I'll start putting it back together over the next couple weeks. Pics to follow.

I would check the skirt t wall side clearance and ring end gap

Great news! Looking forward to your pics.

Any advice on how to do this? I have feeler gauges, but they are flat (1/2 wide) strips. How do you check skirt to wall clearance? Also, how do you know what the ring end gap is once the piston is in the cylinder?

To check the end gap, you put the rings into the cylinder with out the piston. Use the piston inserted into the bore to make sure the rings are square in the bore then you measure the gap with a feeler gauge.

Duh! That's too simple.

Checking skirt clearance is a little more tricky. You can use regular feeler gauges, but it is easier with a ribbon gauge. Ribbon gauges are just really, really long feeler gauges.

Ribbon Gauges:
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Anyway, set the motor on its side. Put the wrist pin in the piston so you can grab a hold of it. Put a feeler on the skirt and insert it into the bore. (See pic below) Once inside the bore, try and rotate the piston. Rotating it checks two things. 1.) that the bore is consistent and true, 2.) if you can rotate it, the clearance is good. You don't want it to slide easy, just a slight "drag", but not tight. It's kind of a "feel" thing. That's why I rotate it. You need to be sure to slide the piston all the way through the bore to make sure it has no tight spots in it. It really shouldn't as it was bored, but better safe than sorry. I check it in a least 4 spots. Put the feeler gauge in at the 12 o'clock, 3, 6, and 9. I hope that makes sense. Oh, if your hands wont fit in from the bottom, you can turn the piston upside down and do it from the top, just make sure you push it all the way through so the feeler gauge comes out the bottom. If that doesn't make sense, I can try and clarify.
Kohler manual says skirt clearance is .007"-.010". Ring end gap should be .010"-.020".

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