Test drive

After doing some carburetor adjustments and minor hood repairs, I took the Little Mule out for a test drive. The engine ran great! I need to tweak the governor a bit, but that's an easy one. Here she is with everything in place, ready for work.

First start

This was the big moment, just before turning the key for the first time. A sound recorder is set up on the tripod ready to capture the event.

A sound clip of the first start is available here (MP3, 1.9MB). Yeah!

Final installation

After lifting the beast in and loosely attaching the bolts from underneath, the next job was to align the block with the transmission input shaft. I performed a partial alignment only, meaning I just ensured that the crankshaft was pointing in the same direction as the transmission shaft. A full alignment would have also ensured that the engine was at the right height - but I don't have the tools and equipment for that.
In the photo above I've got a level on the transmission shaft (visible to the left) and another level on the cylinder head (at the top right). It was off originally, the engine block was pointing up by about 5 or 10 degrees. This would have been another big contributing factor to the broken spring pin problem, certainly. Using washers at the front of the block, I corrected the angle - it's as close as my simple measuring tools can get it.

Just about everything is in place now, gas tank, cooling shrouds, starter/alternator, clutch is adjusted, new fuel lines. Oh and engine oil too (very important).

Linkage confusion

I installed the carburetor and some of the linkages that go along with it, then became stumped again. I wish I had taken a photograph of how it all was assembled originally, but I hadn't. I'm going from memory of years ago when I worked on a similar engine on our farm. Oddly though the memories came back and the mechanisms were familiar.

I picked up the new oil pan gasket today with the clutch parts, and torqued-in the pan. The engine is now ready to go back in to the tractor.

Parts in! -> clutchwork

I picked up the clutch parts today and was able to re-assemble it. The picture above may help to describe what I was trying to explain in one of the recent posts - you can see the three new "special bolts" as well as the shiny new thrust button in the centre. This was just a trial fit to make sure that the new parts mated up properly with the old stuff.


The first piece to go on is shown here - the crank pulley/clutch receiver. This is the part that was damaged, but happily it seemed to go back just fine. To locate the pulley on the shaft I temporarily installed the starter/alternator, but it's not shown in this photograph. The starter/alternator adds about 20 pounds to the engine which is already a hefty 110 pounds by itself, so I'll install that part as late as possible :)


Next is the clutch support bearing. This is a new part, the old one was in tough shape. You can see the main body of the clutch to the left of the photo. I was a bit stumped here, trying to figure out how this thing was supposed to go back together as I couldn't remember how it came apart! Luckily my brother Dave purchased the operator's manual recently and I was able to refer to it for a picture (sadly though the picture was all it offered to help me, other than to say that owners should refer to a qualified IH shop to service the clutch. LOL! The picture was enough.) Since I just recently held the piston in my hand, I guess I'm about as qualified as we're going to get on this project :)
The way the bearing is mounted is a little bit odd from a traditional mechanical viewpoint, but by process of elimination I think I figured it out.

The photo above shows the PTO clutch fully assembled and ready for work. The tiny thrust button is dying to be pushed.

Stripped threads update

The great service you can get from small local businesses never ceases to amaze me. I spoke to Bill at my favourite local machine shop who do a lot of work for the company that I work for, and he was very accommodating. He said "Heli-coils, in aluminum, holes already there? No problem. When do you need it?" Nice. Very nice. Dropped it off at lunch and picked it up after work. He put inserts in all four holes, in the photo you can see the fresh shiny new threads in one of them on the lower right. Cost? $10. Hard to beat.
When I removed the oil pan, the brand new gasket was destroyed of course, so I can't put it back on until the new one arrives (ordered Tuesday from the local IH dealer, should be in Friday).

Carburetor cleanup

The carburetor combines gasoline with air to create the fuel mixture that burns in the engine. I took it apart today fully expecting it to be full of grime from old fuel sitting in there year after year, but was pleasantly surprised - it was as clean as a whistle! All I had to do was wash off the outside oil and grass grunge that had accumulated, a half-hour job.

A minor set-back and some perspective

It's worthwhile mentioning at this point that last summer, after an initial investment of just $200, this tractor cut grass nicely. There were a couple of problems with it though. One was that the engine was old and tired: it burned oil, blew stinky smoke out the exhaust, was finicky to start when hot and had an annoying habit of backfiring. Those problems will be solved with the service rebuild I'm finishing up now.
The other problem this tractor had was that the spring pin that connects the engine to the transmission input shaft had a tendency to break. Like every 20 minutes. It even broke while I was driving the tractor home after purchasing it! :) Actually that first time there wasn't a spring pin in there at all but a POB. I replaced it with a spring pin and thought "great - that problem is solved!!". Not quite. The deeper issue became apparent when I removed the engine from the frame last fall - only three of the four bolts that hold the engine in the frame were there, and of those only one was tight. That improper mounting let the engine slop around in the frame and certainly contributed to the broken spring pin problem (I hope that was the only cause, but that remains to be seen).
The set-back was that when I was tidying up the threads in the engine, getting it ready for mounting, I discovered that the threads in one of the holes was totally stripped. Three out of four isn't going to cut it, so the thread has to be repaired. I chose to use a Heli-coil insert (a relatively cheap and better-than-new repair) but unfortunately that means I need to pull the oil pan off the block again (where these threads are) in order to do the work. This will take a few days. Plus I don't have the tools to make the repair myself: I bought a box of inserts today, but after pricing the full repair kit ($90 for a special drill and tap) I couldn't justify that. I'm hoping that my friendly machine shop will do this for me either for free, or for a token fee. Depending on the cost, I may have all four done at once and then the engine will never vibrate loose again.

Tidbit: Did you know that 250,000 Heli-coil inserts are used on each Space Shuttle? Yes, that's one quarter of a million. Same with Boeing's 747's: each one has over 250,000 of these inserts. Cool.

Clutch update

The PTO clutch that drives the mower was one part that I whipped off last year and hadn't paid too much attention to until last night. This part underwent some hardship at some time in the past (recall from an earlier post the picture of the crankshaft end that was all chewed up - that's where this clutch mounts). It's hard to tell what happened, doesn't really matter at this point. No matter how nicely the rebuilt engine runs, if we can't get power to the blades then this whole effort will have been for naught!
I looked more closely at the clutch and noticed that it had been repaired; there are three special bolts in it, each of which has a dish-shaped head that holds a matching lever in precise location. The three levers keep things centred when the clutch is engaged and disengaged. At some point two of these special bolts were replaced with POBs (plain old bolts), and those didn't keep the levers in the right place so only one of them was actually working. Anyway, I ordered a set of replacement bolts ($7 each) and will be able to re-use the levers, they're fine. There is also a "thrust button" at the centre of the clutch that the three levers engage with - this is the mechanism's G-spot, except that when you push on it, the mower stops working. The thrust button fell out when I disassembled the clutch because the threads on it were gone (broken off). I ordered another one of those as well.
All these parts should be in by the end of the week and won't hamper the progress getting the tractor back together.

Getting ready to re-install

The engine is bolted to the frame from the bottom, and two of the bolts are obscured by the front axle assembly so I had to drop it out of the way.



The pressure washer helped to dislodge 35 odd years of accumulated grunge.


This is what the engine looks like now. Flywheel and shroud are back in place. The new replacement hub and grass screen look pretty good against the new paint job.
Valves are back in and adjusted, and the points assembly (lower left) are in and adjusted. The cylinder head is in place but not torqued yet -- I'll wait until the block is in the tractor for that because it'll just be easier.

Ready for the top work

The engine is now ready for its valves. That will happen another day!

Re-assembly: The Heart

Here is the new piston with the rings installed. The picture is blurry, and that's appropriate because that's how my mind felt after trying to interpret the Chinglish installation instructions that came with the ring kit. Yikes! The Kohler manual, unfortunately, doesn't address these details as the rings come in such a wide variety in the "service" form. I think I got it right. I hope I got it right. Nothing good will happen if I didn't.



Here is the rod mated with the piston. Nice and shiny.




And here I'm using my Princess Auto ring compressor to squeeze the rings down to size so I can fit the piston/rod assembly into the block. The ring compressor is one of the few "special" pieces of equipment I had to purchase for this project. Without it, it would have been nearly impossible to get the piston installed without damaging something. This is one part of the rebuild process where you don't want to cut corners.



Alrighty! Piston and rod are in, and the rod cap (with the long oil dipper you can see here) is torqued to spec. I decided to coat the oil pan gasket surfaces with a gasket compound to ensure it doesnt leak. The machined surfaces were quite a bit rougher than I would have liked (though probably still fine). The compound is just cheap insurance. This is the last time most of us will ever see the inside of this engine, I hope anyway :)

Re-assembly: The Guts

The picture above shows the block with the crank back in, and the camshaft and balance gears also in place. This was one part of the assembly process that I was a bit nervous about because for the engine to run properly (and smoothly) the gears on the crank need to be properly timed (aligned) with the other gears. The last time I rebuilt an engine of this type (about 25 years ago) I recall some stress over this step, but it went fine today. The service manual for this engine is really superb. It was written back in the days when the people who actually designed the engine and built it also either wrote the manuals, or had a hand in them anyway. I had no problems.

At least, no problems with the procedure. I did run into a bit of a snag while torquing down the bearing plate. This is the plate seen to the right of the block in the picture above. It holds one of the main bearings that keeps the crankshaft in place. There is a specific torque spec on the four fasteners that hold this puppy in, and while torquing them down I got them to reach just about spec, then they softened and wouldn't come up. Damn! I first feared that the female threads in the block were giving way - that would have been really bad. I removed the plate and inspected the threads in the block - it was fine. Hum. Maybe a bit of OCD was going on, because I re-assembled the plate the same way and hoped for a better result the next time. Nope. Worse actually, one of the bolts broke. Well that explained what was going on, anyway. I can't quite figure out why the bolts weren't holding, that was a mystery. I noticed a second one was also about to fail. Anyway, I had some stock in the shop and made up four new ones and they torqued up just fine.

There is one gasket under the bearing plate, and a selection of paper spacers as well in the gasket kit - you select the right number of paper spacers to get the correct crank end-play. I happened to guess right with two spacers, giving a crank end-play of about 0.006". Nice and tight.

Painting pics

OK here we go! The picture above is of the block, of course, with the black areas masked off and after the third coat of Cub yellow. Yes, that is a balloon stuffed in there.

The picture below is of the cooling shroud and air cleaner, after three coats of Cub yellow.


In the next pictures the masking has been removed and the important surfaces have been cleaned up with emery cloth. The engine block is now ready for re-assembly. It looks sharp enough that you could almost take this thing out on a date!

Block update

I dropped the block off for machining on Monday, and picked it up today. Pretty good service I'd say! It looks, well, the same really. With the 0.020" overbore, the new piston sits in there nicely and the valves look to be perfectly ground in their new seats and guides. The ball is back in my court now, just some assembly is required and we'll be good to go. I plan on putting up some pictures after I've washed the block of sand blasting grit and oil, and finished the painting with some Cub yellow.

Some painting

I was going to paint the parts and engine block after the block came back from the machine shop, but because of the eBay delays I decided to go ahead and start the painting now. No pictures yet (I'll save that for when I'm done) but so far the high-heat black paint is on the top part of the block (cooling fins) and muffler. It looks pretty nice.

An eBay experience

I elected to purchase the rebuild kit (piston & rings, gaskets, rod etc.) from eBay -- I found the best price there and figured it's time to try eBay out. The Kohler-genuine rebuild kit was about $200 online (this would have been factory-original parts, my first choice) and the local small engine shop would sell an after market kit for the same. On eBay I found one for $105US; after shipping and currency conversion it ended up being about $140 Canadian.
The eBay seller uses a "blanket" item number for the K301 engine's kit -- you need to use eBay 'messaging' to contact the seller after the sale to let them know the exact overbore size and rod size that you need. Sounds simple. I made the purchase as a 'guest' (didn't want to sign up) but they don't tell you that you can't sign in to the message service with a guest account, you need a full account. Argh. They'd beaten me, so I signed up. Then you find out that the message service is disabled for 3 days after initial sign-up, so I couldn't reply to the seller with the details. What fun.

A bit of TLC

This is the cooling shroud that covers the cylinder head - it has a few cracks that I thought I'd repair.

OK the brazing is a little rough. It's not because I'm out of practice, I'm just a ham-fisted welder.

What was gold is now silver

No more Cub yellow here - a few hours with the sand blaster and the old paint and rust are history. A few bottles of spray paint and these parts will be looking like new.

Trying to save the coupling

(Sorry for the blurry picture.) This is the main coupling that connects the engine to the transmission. Two of the four mounting bolts were missing when I removed the engine from the tractor. They were twisted off, probably broken during use I'd guess. I tried to recover this part by using a bolt extractor to dig the broken pieces out, but they weren't budging and I broke the extractor bit inside one of the bolts. Ho hum. For the moment I'm going to let this piece just sit. I'll price out a replacement - it'll have to be pretty expensive to warrant any more work on this thing.

Home measurements #3

The last measurement I was able to make today was the clearance on the connecting rod big-end. In the photo:
(1) Is the connecting rod -- connects the crank to the piston
(2) is the oil dipper -- it helps to splash oil around and lubricate stuff (this engine has no oil pump)
(3) the crank (if the piston is the heart, this is the legs)
(4) the rod little-end (where the piston goes)

I like doing this measurement because it's like opening up a present -- you never know what you're going to get until you take it apart. In the photo above I've installed a small strip of plastic called a "plastigage" inside the joint between the connecting rod big-end and the crank. I've re-installed the end-cap (where the screws are, near the dipper (2) ) with the plastigage in place. I torqued the screws to their spec -- this squishes the plastic strip. Take it apart again and ...

... a paper gauge that comes with the "plastigage" kit tells you the clearance. The more it's mushed, the smaller the clearance. Cool! Result? You can't see from the photo but the width of the smushed plastic shows about 0.003" of clearance -- right on the wear limit called for in the Kohler manual. Right on the edge. This is one measurement that is OK and we don't need to do anything about.

Home measurements #2

OK we need a re-bore. Damn. That means a new piston and new rings. Just for the heck of it I measured the wear on the piston rings. The rings sit in grooves in the piston (see an earlier post for a pic) and seal it to the bore so as it goes up and down gases don't escape around the edges. Very important. In the photo above I've removed a ring from the piston and have installed it in the cylinder by itself. The rings aren't solid like a ring on your finger, they are cut and spring open a bit when you hold them in your hand. When installed in the cylinder they compress and fit very snuggly. The end-gap, shown clearly in the photo above, is an indication of how much the ring has worn. This is an important measurement because you can imagine gases leaking by the little slot that this end-gap leaves open. The gap should be about the thickness of two sheets of paper put together (0.006") but it's more like 0.060" -- ten times too big. The photo below shows how this is measured using feeler gauges.

What does this all mean? A large end-gap like this means lots of gases can escape past the rings, and the engine doesn't perform as it should. Basically an internal combustion engine is a gas pump -- as the piston moves up and down it pumps gases around. Leaky rings means it isn't efficient and has less power than it could.

Home measurements #1

With a micrometer I measured the diameter of the piston. This is not my micrometer but a loner from work. Subtracting the two diameter measurements gives the bore clearance. I won't put meaningless numbers here, but the clearance is out-of-spec which means we need to do something about it.

My friend Surinder

The machinist/engine mechanic had the tools to measure the bore -- this is the diameter of the big shiny hole where the piston goes. I hadn't counted on him doing those measurements for me, but he was willing (call it marketing I guess, since he is the one who'd machine the bore if needed). But I was headed to work anyway as my friend Surinder, a metrologist, had kindly volunteered to measure the bore for me using a hugely expensive piece of equipment called a co-ordinate measuring machine (his baby). I kick myself for not taking the camera into work because it was very cool watching him do this using this very cool machine. Basically the machine is a robot with a little glass ball on the end of a tiny rod called a probe. Think Demon Seed, except there were no unwilling human participants and certainly no DNA involved. Anyway he moves the probe and every time the glass ball touches something it stops automatically and records the position where it touched. Do this a few times, and the machine has enough information to figure out many things -- in this case bore diameter. It is 3.3769". Ooooh! What does that mean? Nothing without more measurements ...

(Incidentally, this measurement agrees with what Fred the machinist measured using a $200 tool, but I feel so much better getting the number from a machine that costs something on par with a nice new BMW sedan ... :)

Machine shop visit

I took the block to the local machine shop for a professional assessment about what it needed. I was there mainly to have the machinist look at the exhaust valve seat, but he gave the whole thing a once-over. He thinks the seats are OK. But, after seeing the intake valve his first impression was "new valves, since it's apart." This scared me a bit since the machining cost will be "about $80 per valve" (and there are two). That blows my thumb-in-the-air machining budget of $100 out the window. Also, he recommended a re-bore as well at a cost of $50 (more on that later).

After the machine shop I took the block into work for some more measurements ...

Bath time

Stinky varsol bath.

Rinsed and dried, ready for bed.

Next steps

1. Measure the cylinder bore. Need to do this to figure out the piston/bore wear and ensure it's within spec.
2. Measure valve guide diameters -- to ensure everything is within spec.
3. Clean
4. Get quote for replacement parts
5. Order parts
6. Back together again!
   

Shiny happy face seats

After seeing that valve the other day I was really worried what the seats would look like -- the other half of the seal formed with the valve face. Luckily, the seat (shown in this photo) looks to be in great shape. It must be made of a tougher material. Since the exhaust valve must be replaced, this seat will need to be professionally ground. I may have the intake valve done as well while it's all apart, if the extra cost isn't too much.

To remove the bent valve I cut the end off with a dremel tool and it popped out pretty easily.

What's going on

This photo shows the edge of the piston that has been worn/burned away. Apparently very common and nothing to lose any sleep over. This piston is reusable.



There are signs that this poor tractor has had a rough life - like in this photo of the PTO end of the crankshaft (valve tappets alongside). At some point in the past the clutch either came loose or the key gave way -- in any case the engine was operated while the clutch ground away on the shaft, nearly ruining it. The red arrows show a clever repair job where the shaft has been pounded with a centre punch to restore its diameter (the key has also been welded permanently in place). This is an expensive part so worth the repair attempt. Likely the person who repaired the shaft was not the same one who bashed the shit out of the end of it.

Mostly empty crankcase

On the bright side everything else looks really good. The cylinder bore is smooth, with almost no detectable wear. All the bits (connecting rod bearings, piston wrist pin) look to be in great shape, this is looking like it will be an easy rebuild after all.

The problem

(Click to zoom)




This exhaust valve is telling a story. The red arrows indicate some serious wear on the face (this area is supposed to be flat). The yellow area shows an edge of the valve that is entirely burned away. This valve is f$%&#@ - it's warped badly enough that it won't come out of the block. I'm not sure what has happened exactly, possibly the engine overheated or was run with the wrong oil (or no oil).

Anyway this explains the oil consumption, oil smell, and backfiring.

Removing valves

Very handy valve spring compression tool saves knuckles.

Flywheel off

Finally got the flywheel off. The process was too messy to describe ...

Minor blowby

I can't wait to see what the rest of the piston and rings look like ...

This flywheel is a sunnuvabitch

Engine out

Rebuilding the engine in this baby ....