78 Spitfire project

[400brian]

So the engine is pulled out of the sled. The sled itself seems like a solid place to start, the track looks good so far, I haven't seen anything yet that looks like a huge issue.

[400brian]

So then I pulled it apart...

[400brian]

So I have been messing with Kioritz engines for 20 years, I haven't seen anything this bad so far. Maybe there is a reason I have stayed away from Kohlers? The jugs and pistons look like junk to me, I am open to suggestions.

[400brian]

OK, so in the four days since I posted the photo of the scored pistons, I have learned a bit. In digging through my inventory, I find that I have a bunch of the Spitfire rings. I don't know what good they are going to do me, but I have them.

I guess there are 2 ways of approaching this; spend no money, just smooth up the pistons, install new rings, and run it until it dies. Which I kinda think wouldn't be long.

The other way would be to go all in, and get the engine as good as you can make it. I suppose I could try to find another engine, but you wouldn't really know if you are gaining much.

The thing is that the engine is over 40 years old. The crankshaft has no detectable end play by eye, but those center seals are a candidate for failure, and I have had experience with that. If you want these to run right, they need to be right. If you want to ride them with some dependability, they need to be as good as you can make them, within reason anyway. I have no desire to spend a fortune on the thing, but I want to run it without fearing that it could crap out at any moment.

So, I am no expert on anything, but I have gained some real world experience with vintage sleds over the past 15 years. In my opinion, this engine is too far gone to cobble up and run, pretty much have to go all in if I want to put the grandson on this eventually.

So, the crank has to go in for bearings and seals, and the cylinders need re-plating. The service manual plainly states that the K340-2FA engine has chrome cylinder bores, and cannot be honed or over-bored. I don't know if anything outside of Aircraft cylinders are chrome plated anymore. Nikasil, a nickle-silicon alloy seems to have replaced chrome for motorcycle, watercraft, and snowmobile cylinders. Millennium Technologies and US Chrome are two companies that quickly come to mind that do small engine plating.

Gasket sets are still available, so that leaves pistons as the final part needed. As near as I can tell, if there are any NOS pistons out there, they are being closely guarded! That leaves aftermarket, and that wasn't looking so good either. Then I found a listing for pistons that showed they fit both the K340-2AX engine, AND the K340-2FA engine. I have never seen a 2AX Kohler, but as I was seeing over-sizes up to .040, I had to conclude it was a iron bore cylinder. So the idea that they might share a piston seemed remote. The bore/stroke of the two engines was the same, but the piston pictured had 2 rings, where the Spitfire piston used one.

Other than the ring situation, the piston appeared identical. I decided to buy a set as they weren't particularly expensive and I have pissed money away before, just to see if they might work. Kohler shared some parts between their engine lines, I knew that the fan cooled K295-2AXY engine used in the model 300 had the same crank as the free air K340-2FA, and with the same bore and stroke, probably the K340-2AX engine as well.

So after I ordered the pistons on-line, the next morning I was flagged on a Face Book post. A guy in Canada had posted a pic of a Spitfire piston side by side with one of these aftermarket pistons. He claimed he had been running them in Spits for 10 years without issue. He did show that they needed to be installed reverse of the arrow on the top of the piston to put both ring gaps between the ports rather than in one.

It appears that the original Spitfire rings were cast iron, and it appears that the aftermarket pistons have cast iron rings as well. I have been in contact with Millennium, and they tell me that any ring other than high content chrome can be used with the Nikasil they apply.

So, the crankshaft has not been removed from the case yet, and I should see pistons in the mail shortly. When they get here, I will put one on a rod and slide a jug on to see for myself how they match up with the ports and if the skirts clear the crank throws and all that.

[400brian]

The new pistons arrived, so it was time to do some test fitting. The old pistons were removed, and a new one put on a rod. I marked where the ring ends were, then slid a jug on.

Here is a top view. The piston is installed with the installation arrow reversed, because if you install it normally, both gaps are in intake ports.

[400brian]

Here is a shot through the intake port with the piston at the bottom of it's stroke, the original one ring piston ring never came into sight here. With the 2 ring piston, the lower ring drops into the port, but not below the teardrop in the center. Which I thought was nice.

[400brian]

OK, that turned out exactly as the guy on FB was telling me, so I think this is going to work fine.

Before I quit for the night, I removed the studs from one cylinder. All the head studs required a little heat, and the top intake stud did as well, but otherwise it was fairly painless.

The clutch needs to come off, then I will split the case and get the crank out. There are a few specks of rust on the crank throws, somebody must have been running the Rabbit oil!

[SS440-80]

This is super interesting

[400brian]

OK, so the Comet Duster clutch needed to come off. I tend to preach buying the correct puller for the job. I bought a 100-102 Comet clutch puller years ago, and I have used it more than I ever expected. My Salsbury puller has been used less, but there really is no good substitute. The puller for sale for these Dusters is a machined rod and a bolt. I don't understand why it isn't a one piece puller like all the rest?

I asked the guys who have worked on these what they used, and of course I got a variety of replies. I decided to try a homemade version of the tool that is for sale.

I took a long 7/16" dia. bolt, cut the head and threads off of it, leaving me with a rod around 4 1/2" long. This will slide into the clutch, and bottom out in the bottom of the threaded hole in the crank. The threaded hole in the clutch is 9/16" fine thread. For the life of me, I couldn't find a bolt that size in my assorted misc bolt drawer. So I had to resort to buying one, I think it is 2 1/2" long. I should have flattened the end of the bolt on the grinder, but I forgot to do it.

I made sure the bolt turned into the clutch nicely, then I installed the rod, and the well lubricated bolt. I used the impact gun because I was not going to have any means to hold things from turning. I turned the air compressor on, and got ready with the gun. My plan was to try it from time to time as the pressure rose. On the first attempt the gun went chunk, chunk, POP! The clutch was off no sweat. Now if it had gone hard, I planned to put some heat to the back side of the clutch as on this engine there was access. I didn't want to mushroom or bend the rod I was using, as that would leave me with the option of cutting the clutch off with the angle grinder.

[400brian]

With the clutch off, I went to work and finished removing the bolts holding the crankcase together. This is a little different than splitting a Kioritz case, as there are shims and snap rings on each end, and the locating dowels on each end fit quite snug.

But I did get the crank out without too much pain.

My assessment of these Kohlers is that if they were good enough, then the Kioritz engines were very much over-built! I will concede that this engine was strictly a 340, while the Kioritz was both a 340 and 440 platform. This Kohler was also a fairly low horsepower engine compared to say the 340/S.

[400brian]

So with the crank out and cleaned up a bit, I took stock of the situation.

The crank seals on each end looked good, however, if you flexed the sealing lip, you could hear it crack. The seals were brittle as egg shells, worst I have ever seen.

I hadn't realized that the Kohlers used a labyrinth center seal. This one turns smoothly, and I think the o-ring is OK.

The mag end and center bearings all roll very smoothly, with no detectable looseness.

Now the PTO bearing is a different story. It is a bit dry, but still it is a bit noisy and DOES have some looseness. I call it a candidate for replacement.

So next I sent a photo of the crank to Jerome Kretzman, who has done all my crankshaft work over the years. Jerome confirmed that what I had there was a lab center seal. As such, he says they rarely go bad, and if they do there is no replacing them. He has a couple month backlog at the moment, and he advised me that if the bearings were good to just run it.

I believe I can remove and replace that PTO bearing myself, so that is the plan tonight.

You will note some rust specks on the throws of the crank. In general the crank seemed very dry when I opened it up. The only oil that was in there was what I had put down the bores doing a pre-tear down compression check. The needle bearings on the wrist pins were very dry. I don't know what the deal was, the Kioritz engines I have opened up have always been very well lubricated inside. I suspect they must have been running the Rabbit oil!

[400brian]

Just a quick update.

Not messing around with this project, spring farm work approaching, taxes, and Easter, all assuming I survive the virus.

I think everything I need is en-route. Crankshaft bearing, gaskets, seals, wrist pin bearings, jugs, all the mechanical parts. I will deal with the ignition when I get there.

[400brian]

I was up to pulling the PTO bearing off the crankshaft. My plan was to wrap the crank up and tape the shaft, then cut the bearing off with an angle grinder. But before I did that, I decided to inquire if my brother had the JD puller for this job. The JD tool set will both pull the outside bearings off, and push the replacement on. After some looking, he dropped what he had off at the garage.

The tool had not been used in a long time, so some clean up was in order. The next issue I found was that the threads on the puller needed to be chased. The nuts wouldn't spin easily on the bolt, but the bigger problem was I couldn't turn the puller into the end of the crankshaft. The threads on the very end of the bolt were dinged, and I wound up having to file a bevel on the very end to get it to work.

So here it is screwed into the crank, the bearing cup is in place and bolted to the puller. You hold the big nut on the end of the puller, and turn the nut on the crankshaft side of the arm to pull.

[400brian]

This puller has seen some use. As I was threading it into the end of the crank, I could detect that the bolt had a slight bend in it, as it would turn easy, then get tight, then repeat...

I wound it up tight, and nothing had moved, I decided to stop and bring in the cavalry. I applied the propane torch to the inner race of the bearing, and in just a few seconds it went POP! I had to pull it all the way, but now it was moving.

In this photo the bearing is off, and the new replacement is on deck. My brother is missing the pipe that is required to push the bearing on with the tool, so I am going to have to scrounge around here and find something that will work.

This puller also works on the mag end bearing. There is an adapter that threads onto the mag end, and then the tool threads into it.
Pretty cool to have the original tool for the job.

[400brian]

OK, been a slight delay, as I needed to source a piece of pipe with a 1 1/4" ID to use with the tool to push the bearing on. The original apparently got separated from the tool over the years.

All I needed was 3" of tube, but a search over 3 farms netted me nothing of the sort. So I had to break down a buy a foot from Wick's Aircraft Supply.

With 3" cut off and squared up, the tool was assembled in the "install" configuration, and the bearing was cranked on.