I opened up the reed cage to work better with single petal carbon fiber reeds. This will help get back the HP I lost by reducing the compression and backing off ignition timing to get this engine easier to start.
The center dividers were removed and the ends of the screws ground flush with the inside of the reed cage.
Since I gave up some power by adding a 1/16″ head shim I decided to improve air flow through the engine by doing a minor porting job. The engine now has a total of 1/8″ head shims which is the maximum and will make the engine easier to pull over. Since the engine runs so well I am not going to take it apart so I can’t do my normal porting job but I can smooth over the dead sharp corners at the intake ports without disturbing the chrome plated cylinder wall.
I have been using the same Chicago Pneumatic die grinder and carbide burr for close to 40 years. Fluid Dynamics was my favorite class in college and served me well when I designed a large industrial flow bench for a pipe fitting manufacturer. I built my own flow bench for SCCA Formula Vee race car carbs and calibrated it to the industrial flow bench. I still have the calibration plates. I used the flow bench on Rokon carbs and cylinder ports years ago. This minor mod and a reed cage mod is worth about a 10% increase in air flow. That translates to a 10% increase in HP on an engine dyno.
I did the port job with the piston closing off the ports so metal would not get inside the engine. I stuck a balled up paper towel in the opening into the crank case.
I finally got the yellow and green paint stripped off the HL134A carb. It was originally painted gold. I will repaint it gold when I have the entire engine back together and ready to paint. It has a couple features that are not on the later carbs. First it uses 2 screws on both the throttle and choke plates versus 1 screw. It has a 1″ bore where it bolts up to the intake elbow but the throttle bore is 15/16″ offset to the top of the carb. The choke plate has 4 flats instead of a hole to allow some air in for starting on full choke.
I did manage to snap off the special throttle shaft in my attempt to straighten it. I was able to replace it with a HL173A shaft. My Rust Bucket MK1 does have a HL134A with the double screw shafts. It was also rebuilt by Mark Wood. I might swap it out if I get ambitious. The Hi needle is 1 1/8 turns out and the Lo needle is 1 1/4 turns out.
The MK0 carb elbow is an Aluminum casting. It is identical to the MK1 carb elbow except both bolt patterns are 1.813″ for the Tillotson HL134a carb. The MK1 JLO LK101L elbow has a 1.813″ bolt pattern for the same HL134a carb and a 44 mm pattern for the JLO engine. It only has provision for the pulse port at the bottom not top and bottom like every West Bend 820 carb elbow I have ever seen. The MK0 elbow has the pulse port drilled, the MK1 JLO elbow does not since the JLO is piston port scavenged not loop scavenged like the Benders.
The 1″ bore MK0 elbow is on the left, a 7/8″ bore MK2 elbow is in the middle and a new US820 1″ bore elbow is on the right in the top picture.
The MK0 elbow is taller and longer and does not require a spacer between the reed cage and elbow like the MK1 and MK2 elbows do.
I noticed the throttle shaft was bent early on. I rode it anyway because I was not going very far from my house. I broke a throttle shaft years ago and I can assure you a broken throttle shaft is a show stopper. I tried to ride the bike home with the idle turned way up but that did not work.
The MK0 throttle shaft was bent maybe 15 degrees which meant it was probably also cracked. Mark Wood had already informed me that it was a special 2 screw throttle shaft and that he had no spares. I decided to confirm that I had a spare single screw shaft and plate before I attempted to straighten the bent shaft. I knew there was a good chance it would break in the straightening attempt……. So I was not surprised when it broke.
I was surprised when I found out that the plate was a different diameter then any HL carb I have ever worked on. Turns out it has a 15/16″ diameter plate. I only have 13/16″, 7/8″ and 1″ throttle plates in stock. The HL134A has a 1″ bore at the gasket face but it steps down to 15/16″ at the throttle plate. So I drilled a third hole in the HL134a plate and installed it using a A1233 high flow screw.
I keep finding these fancy grade 9 bolts so I decided to see what they were used on back in the early 1960s. Turns out they were used on race cars not military aircraft which was one of my earlier guesses. The 2 big ones (7/16-20 UNF) are rear axle adjusters. The 3 1/4-28 UNF ones are for the right front motor mount and the carb to elbow location.
I added a 1/16″ thick head shim to make the 82001 engine easier to start. When I test fit the engine one of the front engine mounts no longer lined up. The engine bracket looks like a MK2 with vertical slots for the bolts. The frame also has vertical slots instead of horizontal slots like later MK2 through MK 7 bikes. A 1/4″ drill bit fixed the issue.
The rear axle stay plates are very different from later bikes. They have no provision for a tow bar and they are made out of 3/16″ steel plate. The rear rack stay tubes are drilled for safety wire to secure the axle bolts that are also drilled for safety wire although no wire was on the bike when I got it.
The adjuster bolts are 7/16-20 UNF instead of 7/16-11 UNC on MK1s and 3/8-24 UNF on later bikes. They are Grade 9 Supertanium Alloy which is massive overkill for what they do. My guess is they either came from Charlie Fehn’s aircraft repair business or the Nethercutt’s race car adventures.
The rear miter box input sprocket is a hot mess. It was drilled at least 3 times for 3/16″ and 1/4″ diameter split pins. It is a Browning 4016 x 3/4″ keyed sprocket. 40 means #40 teeth and 16 means a 16 tooth count. 3/4″ is the bore size. Any other bike this would be in my scrap steel bucket but I will run it because it was working just fine during my first rides. 16 teeth means this bike is very fast for a 2 stroke Albion bike. 25 MPH maybe more.
The picture below shows a 3/16″ drill bit at 1:30 that was drilled through the 5/16-18 UNC threaded hole at enough of an angle to break through the face of the sprocket. There is a 1/4″ drill bit at 4:30 and a 1/4″ split pin at 10:30. The 4:30 hole is tight on the pin but the 10:30 hole was drilled way oversize and does not line up very well with the 4:30 hole. The miter box only has one slightly off center 1/4″ diameter hole. The 1/4″ pin only goes one way. I will use the 1/4″ pin with 2 or 3 loops of safety wire through it and a 5/16-18 UNC set screw shown at 1:30. The miter shaft is not keyed.