The Rotary Valve Engine II
Here we go with part two.  The head, valves and accessories.

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The Rotary Valve Engine III
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11 October 2016:
Now, to the head.

I finally got the nerve to start on this part.  It took some figuring to determine how to machine this 6"+ hunk of cast iron.
Milling a reference end.                                                                       Cutting to length.
Since the hunk of cast iron was saw cut, the ends weren't perpendicular to the side walls so I shimmed it in the mill to get it close.  The end that will end-up against the cylinder (the combustion end) was then milled flat.  This will be the reference surface for the other end which will house the valves.  I also drilled and tapped a couple of holes for 3/8-24 bolts that will be used only for holding the combution end of the head to the face plate.  This weill allow the other end to be faced.  These two bolt holes will not be used for anything else and won't show once the head is mounted.  

Since the piece of cast was over a half inch too long and I didn't feel like making a career out of facing it to length, I sawed off that piece and saved it for something or other.   

After facing cut end, turning the O.D.                                      Marking it so I don't screw it up!
Out of the saw, it went onto the face plate in my dinky lathe.  Facing it wasn't a biggie.  It just took some time.  The O.D. was too big to turn using my regular tool bits because they can't hang out far enough to do the job without the carriage banging into the workpiece.  What I did was to dig out one of my honkin' big brazed carbide bits that I'd earlier modified so they would fit in my tool holder.  I was braced for a bunch of chatter but was surprised when I could take 0.010" cuts at a relatively fast feed.  That got the O.D. down to 6.125".

I got the piece sawed off just a little short in spots (I had to turn it as it cut so it wouldn't cut a slant that would have made it a LOT undersized).  No matter, because the parts of the face that didn't completely clean up are going to have a lot of metal hogged out and they will disappear.  I just marked the piece the way I wanted it oriented in the mill and will drill and tap for the two 3/8-24 bolts that will serve to mount it to the face plate to turn the combustion chamber and, later, to act as hold down bolts for the valve pressure plate.
14 October 2016:
Well, today was one of those "What was I thinking??!!!" days.

It looked like I was making good progress, getting the head bolt holes drilled and the sideshaft support mount milled out.  Then, when I went to do a test fit of the head..........
The flat on the back of the head is supposed to be PARALLEL with the back of the engine!
THAT screw-up happened a couple of weeks ago when I was finishing the drawings for the top plate of the crankcase and the cylinder.  I somehow got the bolt holes exactly 30 degrees off of the orientation they needed to be.  At first, I thought I could just re-drill the head to match the cylinder but two of the opposing bolts are supposed to be at the bottoms of the valve bores.  If I tried to re-drill the head, the holes would interfere with those bores.  DRAT!  Now, I'm going to have to pull the piston, remove the cylinder and re-drill the base bolts so the head will be correctly oriented.

I think I need to put on my red bulb nose and big floppy shoes along with the clown suit.  What a Bozo move!

There's a show in Blountstown, FL tomorrow that is a day trip so I think I'll just haul some of my junk to show.  Maybe that will be a good brain reset. 
18 October 2016:
I took it apart and now have the base of the cylinder re-drilled so the head is oriented correctly.  I'm working on figuring out how to fit oil collectors for trhe mains.  When I took it apart, there seemed to be a few little oil droplets around the oil holes for the mains but I will still make an improvement as insurance against them running dry.

I'll be back at it in a couple of days.   
19 October 2016:
Well, I decided to do some more on the engine today despite thinking I would be taking a day or two off the project.  I did get the oiler funnels made and got the engine back together.

Oiler funnels for the main bearings.
It took some fiddling to get the oilers made and fitted.  There is very little clearance between the funnels and the crankshaft counterweights.
20 October 2016:
The outrigger bearing for the top of the sideshaft is done and the spark plug hole is drilled and tapped.
                   Drilling the outrigger.                                             Testing gear fits and ready to press the bushing in
In the right hand photo above, the gears are shown upside-down and I placed them above where they go to make sure I hadn't done a Bozo on the spacing.  It all looks like it will fit.  

The next part is close to the most complicated part of the engine.  I have to turn the gears and face them to exact dimensions.  The hubs of the gears will then fit into bores in the head.  This fit must be a good one because that's the bearing fit for the gears.  There will be a larger bore concentric with and above the hub bore to clear the gear teeth.  As you will see when I get to it, I have a piece of 1/8" oillite bronze that I will cut to fit in the bottoms of the bearing bores to act as wear plates for the faces of the gears which will be machined into the valves.  On the other side of the gears, I will cut a piece of PTFE (Teflon) to act as a top bearing.  There will be a plate to cover the gears and apply slight (I hope) pressure to the valves so they will seal.
21 October 2016:
With the top sideshaft bearing pressed and fitted, I thought we should see what it looks like with the head on.

With it's head on.
Then, since I couldn't think of any way to delay finishing the head and valves, I started by carefully turning the valve gear hubs to an accurate diameter so they would run smoothly in the head.  After that, the faces were finished to size and lapped smooth.

The head was mounted in the mill,squared-up and the center found.  The "boring" work commenced.  It took about three hours to do what you see on the exhaust valve bore.  

The hub/bearing bore is done for the exhaust valve.
It is now finished to the hub diameter but the major diameter must now be bored.  I hope to have the bores done for both the intake and exhaust valves and possibly have the slot milled across the head tomorrow.
22 October 2016:
Well, I got the "boring" job done and it took all day.
              One bore done.                                                                  Both done with one gear in place.
I just knew it was too good to be true.  Each gear hub fits with about 0.001" clearance, which gives a really nice fit.  The big AW-SHOOT it that somehow, I failed to give the gear teeth any clearance.  I can -almost- get both gears in place but they jam about half-way down into their bores because of tooth interference.  I think what I'm going to have to do is to turn about a half-thousandth off the hub diameters of both gears.  this ought to give clearance so they will run free.  The fit of the gear hubs with the bore in the head will be all right.  As a matter of fact, the gears are a bit tricky to get slipped into the bores because the fit is so close.

Oh, yes - the head bolts at the bottoms of the valve bores was part of the plan.  There was just no way that the six bolts (or four bolts) could be oriented to not have a couple in the valve bores.

I'm a bit intimidated by machining the valve ports.  One little slip-up and the head is trash.  I'm also going to have to devise a method of mounting the head on the rotary table with the valve bores centered on the axis of the table.  The problem is that the head is bigger than the table and I'm going to have to use some imagination to make it secure.

Oh, well - tomorrow I'll fit the gears and make the bronze thrust plates which go in the bottoms of the gear hub bores.  I plan to use epoxy as bedding between the head and the thrust plates and to seal them to the head.
23 October 2016:
I didn't do it like I proposed yesterday.  Instead of turning the hubs down 0.001" or so, I re-mounted the head in the mill, squared it up and found center then ran out to the center of each gear bore.  I added 0.001" distance from the center of the head and bored the diameters until they just cleaned-up all around.  The fit is still very nice and, surprise - the gears fit well with just a slight hint of clearance and no drag.  I guess I lucked-out once more.

The gears now fit!
Next on the agenda was to make the bronze wear plates for the bottoms of the bores.
Friction driving to turn O.D.'s.                                                                First rough lapping.  
Before cutting the thrust plates out of the stock, I laid-out and used a 3/8" end mill to make the clearance holes for the head bolts.  Since hanging onto the 1/8" thick disks is problematic, I used the face plate and a live center in a punch mark to drive them so I could turn the O.D.'s to size.  Using a sheet of glass and some 180 emery paper, I then rough lapped them to near flatness.  I figure that, if the valves tend to leak, I can use Time Saver lapping compound to run them in.
                     Checking fit of the thrust plates.                                  Anti-rotation grooves cut in bottoms of thrust plates.
After making sure everything lined-up, grooves were cut in the bottoms of the plates.  The grooves are to keep the plates from turning.  
      Epoxy was buttered on bottoms of thrust plates.                       Head with thrust plates and valves in place and in press.
In order to ensure that the thrust plates were an exact fit with the gears, steel filled epoxy was buttered onto the plates and they were pushed into the head.  Before this, the bottoms of the bores were cleaned with acetone and grease was applied to the gear faces and hubs as well as the insides of the bores and the bolt holes were also greased.  This was so the holes could be easily cleared after the epoxy sets-up.

To make sure everything settles down, a bar was put across the gears and the assembly was put in the press and about 100lbs of force was applied.

Now, if all goes well, I haven't glued the whole works into one totally locked-up chunk.  Tomorrow, we'll see if it comes apart.  
24 October 2016:
Well, it did come apart after a bit of persuasion.  The excess epoxy had squeezed up between the bore and the gear hubs.  Although the grease kept it from sticking to the parts, there was zero clearance and it took a bit of persuasion to get them  apart.
Here it is right after disassembly.  Note the epoxy that squeezed up into the oil clearance.
I then drilled, tapped and countersunk two holes in each thrust plate for 4-40 flat head brass screws to make sure the thrust plates cannot turn.  This is kind of like wearing a belt plus suspenders but is cheap insurance against the thrust plates turning.
Showing the belt/suspenders arrangement on the thrust plates.    Stuck together to check running.
I will have to do a bit of re-sizing of the bushings for the sideshaft.  Due to a very slight misalignment, they are binding.  When I set them up, I had them fitted fairly tightly.  A couple of thousandths of clearance will make the shaft run with much less drag.  I will also have to adjust the gear position on the end of the crankshaft.  It is just a bit too far out on the shaft, causing the gears to be noisy.

Facing the top plate.
Then, it was on to making the top plate which sandwiches the valve gears with a PTFE (Teflon) thrust bearing.  This will mount using studs in the two 3/8" holes in the head.  I will only use two studs because I want the plate to be able to pivot between the valves to allow for uneven wear in them.

I also removed the flywheel end main bearing and honed it a bit.  I noticed that it was getting hot and beginning to bind when motoring for several minutes.  It now runs a little warm and has lost the tendency to tighten-up.
26 October 2016:
I got the sideshaft bearings honed to a nice fit and there is no more binding.

I then finished the top plate and made the PTFE thrust plate for the top of the gears.
  The PTFE thrust plate.                                                              Top plate mounted.
The PTFE thrust plate is attached to the top plate with 6-32 screws at the centers of the gears (valves) so it doesn't wander and stays registered with the intake and exhaust passages in the head.  Right now, I just have some junk-box springs putting pressure on the top plate while I run the gears (valves) to lap them into their bronze thrust plates.

The intake port is on the sideshaft side of the head and the exhaust port is just opposite it.  These ports register with the valve and head ports.  I may have to enlarge the ports from the present 3/4" diameter to something like 1" if it doesn't breathe well.  They'll probably be all right as they are because I don't intend to try for 500 HP.
27 October 2016:
Well, I went ahead and enlarged the ports so I wouldn't have to do it later.  Then, I made the manifold, exhaust pipe and the throat of the mixer.

Mixer throat on left and exhaust on right.
After getting the manifold finished, I lapped on the valve seats some more.  They are getting there.  Even without a head gasket, if I stick my finger into the spark plug hole, there is plenty of compression.  The motor isn't powerful enough to spin the engine with the spark plug in because I have yet to find a flywheel to help it over compression.

I'm about at the point where I will have to stop lollygagging around and start on the valves.  They are going to be a challenge.
29 October 2016:
I finally worked-up the nerve to start on the valves.  I made a mandrel to hang on to the gear, centered on the center of the rotary table.
        Drilling the cutter guide holes.                           Milling the first 0.100 depth of inner slot.
I had previously clocked the valves so, when the timing marks line up, the engine is at the overlap point (top dead center at the beginning of the intake stroke).  After centering the rotary table, I mounted the gear (valve) so the timing punch mark was at the lead angle on the table.  Then, I rotated the table to zero.  That was the centrer of the arc of the valve port.  I drilled a couple of 0.235" holes at the centers of the inside and outside arcs so I could plunge a 1/4" milling cutter all the way through the gear.  Everything started off fine until..........
You don't want to know what I said when this happened.
Even though I was feeding it slowly and only to a depth of 0.100", the brand new solid carbide cutter snapped.  Since I don't have a drawer full of carbide cutters, I had to resort to one of my old high-speed steel cutters.  Because the H.S.S. cutters can only go to a depth of 1/2", I had to get creative.    
Milling the outside slot with a H.S.S. cutter.                                              Finishing the sides of the port.      
After modifying the hold-down nut for the gear (valve) so it would clear the 3/8" shank of the cutter, I finished cutting the port out for the exhaust valve.  This part worked-out just like I planned it back in Part I.       
Manifold end of valve.                                                            Head end of valve.
As you can see, I used a high speed steel milling cutter that had only a 1/2" depth of cut.  Since the only place where the ports are "timed" is where they meet at the head port, I could get away with milling a 3/4" round hole down to within 1/2" of the head end of the gear.  This let me get away with only milling the head end to a depth of 1/2".
30 October 2016:
Today, I can see the limitations of my machinery.  After finally getting the head set-up on the rotary table, when I started on the valvc ports in the head, I found that I wasn't able to hold on to the head securely enough and it moved a little but I don't think that will be a big problem.  I solved the clamping problem then found that my milling cutter wasn't long enough.  The ones I've got left after breaking the carbide one will only mill 1/2" deep and I need to go almost 3/4" to breaak through to the combustion chamber.
Milling the intake port in the head.                                                       Modifying the milling cutter.
The cutter length problem was solved by chucking it in the lathe and using my wonderful Dremel tool toolpost grinder.  It took a while but I got the shank diameter down to 0.240", extended 1/4" to give a total reach of 0.750"

Tool creep marring finish of bronze thrust plate.
I decided to quit for the day when I found out that, since I have to have the cutter extended so far from the collet, it creeps down.  This put a mark in the thrust plate but I think it can be lapped out.  You will also note in the photo above that the arc angle is too great.  This is because the head slipped on the rotary table.  I'm going to go ahead and finish it.  If the valve timing is too compromised, I will remove and scrap the present thrust plate and make another one.

I think I've got a fix for the cutter creep problem.  What I've decided to do is to modify the top of the head to give room for the quill to go farther down and allow the milling cutter to be seated more fully in the collet. This modification will have no effect on the engine but is just another machining step.
31 October 2016:
I got the head modified today and finished the intake port.  I'm really not happy with how it turned out and may have to do the thrust plate again.

The head modified to allow the end mill to be more firmly held in the collet.
I just noticed that, somehow, my camera got it's settings scrambled so now I have nice antiquey sepia photos.  I'll have to go back and see what is amiss.

Anyway, since the end mill that crept out of the collet got chipped, I had to use my dremel toolpost grinder to make another one.  With the extra room for the quill of the mill, I can seat the cutter deeper in the collet to make it stay put while I do the exhaust valve port.

More in a couple of days.
3 November 2016:
The exhaust port is finished and it turned out a lot better looking than the intake.  With the extra machining relief in the head, the cutter didn't creep a bit and the cuts were a lot smoother and more accurate.  It took all morning to make the exhaust port.

Showing the exhaust valve about 3/4 of the way to the end of it's stroke.
I wasn't sure the duration of the intake valve would be okay because of goofing on the angles but, after putting it together and setting it in time, I get the exhaust opening about 20 degrees before BDC and closing right at TDC.  The intake is a bit radical.  It opens maybe 5 degrees before TDC and closes at about 5 degrees after BDC.  That should work fine.

I ran it on the motor for a few minutes then stuck my finger partially into the spark plug hole (the motor won't drive it under full compression with the wooden wheel).  It didn't seem to have any suction on the intake and no pressure on the exhaust.  I took it back apart and found that the sideshaft gear setscrew wasn't tight enough and it slipped.   After setting it back into time and motoring it, there was suction on the intake and pressure on the exhaust so I must be satisfying Herr Otto's requirements.

Now, I'm nearly stopped dead in the water because I have no flywheel.  Tomorrow, while I'm out and about, I'm going to go to a sporting goods store and see if I can score a barbell weight.  It should do and will be a lot easier than making a wheel from scratch.  

What I really, really need is for some kind soul out there to have a flywheel about 12-16 inches in diameter and about 1-1/2 or 2 inches wide that will fit a one inch shaft.  I'd be willing to buy it for a reasonable price.  Of course, I can sleeve it if hub is too big.  Because of the limitations of my machinery, if it's over 11 inches in diameter, I won't be able to bore the hub out and will have to take it to a machine shop but that will be a lot easier than making a wheel out of a gob of cast iron.  Been there - done that!  WHAT'CHA GOT??
4 November 2016:
Today, I scored what I think will be the flywheel.  I found a 25 pound barbell weight at Wal Mart.

This looks like a flywheel that has been unfortunately placed in the sports gear department by mistake.
It is about 11-5/8" in diameter, about 0.100" too big to fit in the mill.  I think if I remove the chip guard, it will work.  Tomorrow, I will see.  The I.D. needs to be cleaned-up and fitted with a bushing to fit the 1" crankshaft and the O.D. needs to be cleaned-up so I can run a belt on it.  
5 November 2016:
After removing the chip guard, the weight -just- cleared.  By about 0.050".  I bored the hub to clean it up then made a bushing to reduce the bore to 1.001" to fit the crankshaft.  I'll do some cosmetic work to the wheel (remove the "Gold's Gym") and finish the O.D. then press in the hub after I get the setscrew hole drilled and tapped.  After that, maybe it will get a coat of paint.
Just barely fits in the mill.                                                                            The bushing.        
I'll finish up the flywheel except for broaching for the straight key (I've loaned out my broach set).  Then, it's off to do the carburetor, governor and the ignition.  Speaking of carburetor, I still haven't decided whether to fuel it with gasoline/naphtha or LP gas.
6 November 2016:
The flywheel is done except for the cosmetics.  As you can see below, I milled off the advertising print and will fill and sand the millling marks before painting it.  I've gotta admit, it makes a pretty fair looking flywheel.
Cleaning-up the O.D. of the wheel after de-branding it.                                            Going for a test spin. 
After pressing the hub into the wheel, I made a mandrel to fit my largest mill collet and bolted the flywheel to it.  Then, using the mill vise as a tool holder, I gingerly turned the O.D. until it was cleaned-up.  

The wheel was then mounted on the engine using a bolt seated in the keyway to hold it secure and it was given a spin.  It has enough mass to allow it to go over compresison without stalling the motor. I had to tighten the hold down bolts pretty tight to keep compression from lifting the top plate.  Using my trusty auto compression gauge, I measured around 50 PSI, enough for it to run.  I think there was some valve leakage so I will motor it for a while to see if it improves as the valves and seats wear-in.
9 November 2016:
Not much to show for the last couple of days.  I got the milling marks filled-in and sanded and painted the wheel with some left over blue/black paint I used on the Model T coil tester.  

I also re-vamped the top thrust plate hold downs.  The springs had to be totally bottomed-out for the valves to seal decently so I made some long studs and big nuts to non-resiliently hang on to the thrust plate.  After motoring it for a few minutes, the compression rose to 60 PSI and the drag of the valve train was less.  I'm thinking it's going to take more motoring it to get the valves to seat properly.

The partially completed mixer.
Then, today, I started on the mixer.  This is what I call a fiddly bit.  It's not a complicated thing but takes a lot of piddling around to make a proper throttle butterfly and fuel needle valve assembly.  I may finish that part tomorrow or Friday.

I've thought a little about the linkage between the governor and the mixer but haven't put anything on paper yet.
10 November 2016:
The mixer is done.

Mixer and hold downs.
Next up is the governor and I'm going to use CAD to design it.  I'd like to try something unusual but haven't had a lot of luck with oddball stuff.  I'll think on it.

Oh, yes - the compression's up to 65 PSI after motoring it for another 15 minutes.  There is still some leakage, though.
14 November 2016:
I've got a design for the governor and will start on it this afternoon.

Here's what I think the governor will look like.
To keep the height down, I decided to do away with the links above the governor weights and hold them on a horizontally rotating shaft.  As speed increases, they slide out on the shafts and in so doing, raise the inside ball bearing race that slides vertically on the sideshaft extension.  The inside race is a press fit with what I call the rotor.

The outer race of the bearing (the stator) does not rotate but moves vertically with the inner race and rotor to pull on the link from the outer race mount to the bellcrank.  I have designed-in some adjustment holes on the throttle arm to adjust the sensitivity.   The ratios are calculated to give nearly full throttle motion when the weights reach their stops and when the link is at the top-most (least sensitive) positon.

I do not show a governing spring but will include one most likely working against another arm that will be located on the bellcrank shaft.
15 November 2016:
Some of the parts are done.

The partially completed governor.
There were a couple of Bozo moments today but no harm, no foul.  I know you will never tell!  Anyway, all of the critical dimensions are right on the money, within 0.001".  Once I get the slots milled (sawn?) and the pivot holes drilled and tapped, the weights will be finished.

The sideshaft extension is made from a hunk of a mystery alloy of 1.250" diameter steel.  Try as I might, it was Chatter City and I could not get a good finish on it.  From now on, my turning stock is going to be leadloy.
16 November 2016:
Moving right along, still working on governor parts.  Just completed part the stator along with slitting the clevises on the weights and making the pivot pins.  

The completed stator.
Either I was very slow today or I was having a lot of fun because time passed quickly before I got a whole lot done.  Short day tomorrow but I hope to finish the governor and linkage over the weekend.
17 November 2016:
Today I got the rotor part of the governor and the arms done.
       At low speed position.                                                                   At high speed position.
Next will be the belcrank and pivot.  I'll lay out the positon of the pivot block directly on the head.  The belcrank is now going to be in two pieces, separated by a shaft to provide the offset between the centerline of the sideshaft and the throttle arm on the mixer.
19 November 2016:
The governor and throttle linkage are done.

Here it is all put together with the gear guard in place.
The photo shows the engine being motored with the throttle a little over half closed.  Note the springs on the sideshaft extension.  I may have to change the springs to get the speed right because it would probably be running a bit slow as it is right now.

Note the gear guard.  I've decided that I have donated the only fingertip I'm going to part with to these projects.  This gear attracts my hands so it is now out of reach unless I really work at it.

Tomorrow, I'll start thinking about the ignition then the mixer venturi, fuel tank and check valve will be addressed.  At that point, it will be ready to give it the first smoke test.
20 November 2016:
The ignition is figgered out and I made a fuel tank.

Ignition timer and fuel tank.
The ignition timer is made using a shaft collar with a small magnet attached that will go on the sideshaft.  The sensing is by a magnetic reed switch mounted in an aluminum sleeve that is concentric with the sideshaft.  Simple and workable.  The timer mounts at the top of the lower sideshaft bearing.  The sensor sleeve has a wing bolt that locks it against rotation by clamping it to the outside diameter of the bushing.  Loosening the wing bolt and turning the sleeve changes the timing.

The fuel tank is made from a six inch section of brass pipe I bought at a scrap yard.  The end caps are made of some 0.015" brass sheet, cut in oversized circles and, using a swedging plug, pressed into the ends of the tank and soldered into place.  I will use the gear clamps to attach it to some kind of frame that is mounted on the side of the engine.

I motored it some more today and hope that, with more motor time, the valve leakage decreases.  Right now, I'm getting 65 PSI compression with slight leakage.  I really don't want to have to run the top plate too tight because it puts a strain on the gears and allows the possibility of galling or seizure.

We're getting close, gang.  Once the fuel check valve is made and the timer and tank mounted, it will be time to see if we have internal combustion happiness.
22 November 2016:
Just got another couple of small things done.  I finally got the keyway in the flywheel broached and have made a key.  Then, I got the ignition timer on and set.

The ignition timer.
Tomorrow, I may be making a video of the first attempt to start it.  That all depends on how mounting the fuel tank goes.  Stay tuned.
23 November 2016:
I got as far as hauling the tripod out to the shop, thinking I just might be able to see if it will make smoke.  Not yet but I did get almost all of the remaining fiddly bits done.
Venturi and the incomplete flutter choke.                                               Here they are on the engine.      
The front gear guard.                                                               The rear gear guard.
To save my fingers, I went ahead and made the other two gear guards.  Not the prettiest things around but they should keep my pinkies safe.

Not shown is the fuel tank mount which is sitting with drying paint.  

Tomorrow is Thanksgiving so I will not be out in the shop but about all I have to do now is finish the flutter choke, make the fuel check valve and mount the fuel tank.  Maybe the next full shop day will be the moment of truth.  
25 November 2016:
Today, I got the flutter choke and check valve done and the fuel tank mounted.

Engine ready to run.
I made the spark plug wire, put in a new spark plug and started the video camera.
And, here's the flick.
Yayyyyyyyy!  It runs.  On the first cranking, it actually fired a few times and ran off the belt on the second try.
26 November 2016:
Today, I got some more run time on the engine.  After thinking on it, I increased the size of the venturi neck from 0.250" to 0.280".  This allowed it to breathe a bit better and it would pull the motor with the belt attached and the motor turned off.  I suppose that, before lunch, I got about 30 minutes of interrupted run time on it and the main reason it wasn't continuous is that the valves would get hot and bind.  After it stopped for lunch, I checked the temperature at the top of the cylinder and it was around 200F with no fan.

After lunch, I jury-rigged a fan to the engine and ran it again for about a half hour, not counting the stops for binding.

Running with cooling fan attached.
When the run ended, I again checked the temperature and it was now about 180F, so the fan did some good.

The run ended with a snap.  I heard the engine laboring from the binding valves but before I could stop it, the sacrificial aluminum screw holding the sideshaft gear to the crankshaft sheared off.  At this point, I was getting tired of fiddling with the top plate tension so I removed the valves for a looksee.
As disassembled, showing the leak paths.
                     The exhaust seat (foreground) after cleaning.                 The seat side of the valves after cleaning.  (left is intake, right is exhaust)..
As you can see, it was a mess.  No galling, etc, but the oillite seats in the head show where the leakage is occurring.  Some thinking is needed to figure out how to stop the leakage so the force holding the valves against the seats can be lessened.  It could be that the bronze just needs to be lapped more but I'm reluctant to remove any more material than absolutely necessary.  Also, before cleaning, the seat faces were dry of oil, which may also be a cause of the binding.  On top of the valves, the Teflon seems to be working fine.  There is no appreciable wear showing on the plastic and the faces of the valves (gears) are nice and slick.

You can see the carbon tracks where the valves leaked on the periphery of the seats.  I suppose, in retrospect, I should have designed the ports smaller so they didn't run so close to the outside edges of the valve sealing faces.  There doesn't seem to be any leakage on the insides, although there is really no place for the leakage to go in that area.

I suppose I could groove the hubs of the gears and put-in piston rings to isolate the leakage but that has a downside in that it gives the entire area of the faces of the valves to help them try to shove themselves out of their bores.

29 November 2016:
After doing something else for a couple of day, it's back to the job.  Since I couldn't lap-out the burn spot in the exhaust port and the bronze didn't appear to be flat, I made a tool to refinish it.
The tool, ready to glue on the sandpaper.                                         Flattening the seat.      
I took some aluminum and turned a tool to re-face the valve seats.  Sandpaper glued onto the flat surface of the tool, it was mounted in the mill and, at the slowest speed, was gently lowered to the seats.  After a few seconds, it was raised and the bronze was cleaned off then the operation was repeated.  After getting a good flat surface on the seats, lapping compound was applied and the valves were worked until they showed good contact.

After all this, the engine was re-assembled and motored for a few minutes with the spark plug out.  When the plug was installed and the engine started, the valves still leaked.  Dang!!  More thinking is in order.  I'm leaning toward a sealing ring (either Viton or cast iron) to eliminate most of the leakage.  We'll see.  

2 December 2016:
Over the past few days, I've been working on a way to seal the valve seat area to minimize leakage past the seat.  Here's what I've come up with.
       The red line shows where the O ring will go.                                      Exploded view of how it will all fit together.

I've decided to use a square cross section silicone O ring.  Silicone is good for up to about 500 degrees F, so should be able to take the heat.  This will only allow the seat to leak until the area below the O ring is pressurized.  Since this has very little volume, it shouldn't materially affect the compression ratio.  Because of this arrangement, there will be a lot more area under the valves and more pressure trying to push the top plate off of the head.  The Law of Unintended Consequences have been taken into consideration but that still doesn't mean something will go horribly wrong when the engine is started.

What does concern me is how the O ring will work in the rotating fit.  I consulted O ring design guides for dimensions of the groove but the guides aren't specifically for square cross sections.  It worked out to have about 0.015" squeeze between the bottom of the groove in the valve and the valve bore.  This seems to be a little on the tight side but I will try it.  I'm getting a package of five rings so, if it doesn't work, I will be able to machine the groove deeper and try again.

The rings are ordered and should be in by the end of the weekend.  This works out because my lathe is torn down to replace the bronze gear in the carriage feed drive which has (again) worn out.  I won't be doing any lathe work until it arrives and I can put the whole works back together.
BOY!!!!  This is FUN!!!
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