Gas cap

The old MK0 picture shows what looks like a quarter turn gas cap on the bike. This bike has what I suspect is a replacement MK2 gas tank because it has no green paint underneath the yellow and a fine thread MK2 plastic gas cap. I also suspect the original gas tank, wheels and muffler came from the 4a Maico bike which also shows a quarter turn gas cap. Since the fork was tweaked about 5 degrees from a misadventure it is not difficult to believe that the gas tank got damaged and was replaced at some point.

I am not sure why there are disk grinder marks all around the gas cap filler neck. I decided to look into a period correct replacement cap and came up with a late 1950’s Harley cap and filler bung that looks real close.

I took careful measurements and figured out what size hole saw to use. I turned down one of my old fine thread gas caps that I have been using as a painting mask to fit closely inside the hole saw. I also drilled a quarter inch pilot hole in the cap to help guide the hole saw. I screwed the modified cap to the filler neck.

Harley filler neck test fit.

Hole saw.

Ready to be brazed.

Exhaust manifold studs

The exhaust system is a welded fabrication that matches the exhaust port on the Power Bee block quite well. It was fastened with 2 5/16-18 UNC hex head bolts with 1/2″ hexes. The top one was easy to get to but the bottom one is a project requiring quarter turns with an open end wrench. I have been trying to use the original hardware wherever I can but this manifold needs my A1237 stud kit big time. The stud kit reduces the chances of cross threading and or stripping the engine block threads. The 3/8″ hex jetnut (rated for Mach 2) allows using a box end wrench in this tight location. The jetnuts are self locking but I like to run a tap through them because I am old and have no patience.

Clutch cable clip

I thought I would detail the little clip that keeps the clutch release cable from getting tangled up in one of the chains that are spinning inches away. It was painted green underneath the yellow so green it is.

Installed. Looks like I did not get all of the yellow out of the screwdriver slot.

Doherty twist throttle

The MK0 has the same Doherty twist throttle that both of my MK1s have. The rubber grips are in great shape so I will use them. One problem I noticed awhile ago is that there is no adjustment for the cable which is about 3/8″ too long. Both ends have soldered balls so I did not want to cut the cable to shorten it. Both of my MK1s have replacement cables that I cut too length. So I had to turn the throttle maybe 1/4 turn before the throttle shaft would even move. With the twist throttle WFO I was getting only 3/4 throttle at the carb. The bike was plenty fast at 3/4 throttle so I did not mess with it.

I really wanted full throttle and I had noticed before that my 04-257 twist throttles looked a lot like the 1962 Doherty. I grabbed one and soon realized they are almost identical except for the rubbers and the adjuster on the 04-257.

I removed the adjuster and compared it to the old Doherty. Turns out all I have to do is tap the old casting and then I can fit the adjuster to the original throttle. So I measured the threads and found that they are M9 x 1.25. I have a fairly complete metric tap set: M6, M7, M8, M10, M12, M14 and M16 in fine and coarse pitches. I do not have a M9 x 1.25…… So I now have one ordered.

Of course I am annoyed but now I decided to find out just how similar the new and old throttles are. Turns out they are interchangeable with some minor deburring. I installed the lower adjustable piece on the old Doherty top piece and it fit.

This will work until my new M9 x 1.25 tap shows up. The adjuster now allows me to get full throttle on the scooter.

Brake rebuild

The front brake worked quite well but it was not aligned very well so one of the shoes wore crooked. I was able to buck the loose rivets to get another 1/32nd of life out of the worn shoe. I decided to clean and paint the backing plate and put the brake back together as is because I want to use the bike soon for Morel hunting. The backing plate is pinched between the fork and the end of the 5/8″ diameter axle. The hole in the backing plate is 1/2″ and the bolt going through it is 3/8″ so there is a 1/8″ gap which the axle had fallen into on one side making the shoe alignment even worse. I found a white 1/16″ thick O-ring that I will use to center the brake backing plate better than it was.

The shoes are difficult to install with a nasty learning curve which reminds me of the first 20 times I struggled attempting to re install Rokon front miter boxes until I figured it out. Cusswords and big honking snap ring pliers finally overcame the heavy springs.

I cleaned up the hardware. The threads are 3/8-26 BSC (British Standard Cycle).


The 58 year old Firestone Power Implement tires are in excellent shape with little wear and no cracking. I set the MK0 front tire up against my MK1 Firestone to show how much more tread they have. These are 4 ply rated and probably would work great on an off road lift truck since they are rated for 1280 pounds each. They require no air pressure. I did not remove the axle and bearings on the front wheel. I plan to use them as is since they are still running smoothly. I did have to remove the rear axle since it was bent.

Hand clutch

This post details the assembly of the hand clutch to the Albion 3 speed gearbox. This is the heavy duty version dual disk Albion clutch. It uses cork for the friction material and new corks are available in the UK. The intermediate fixed disk was missing so I had to grab one from my stash.

Engine and Albion installed

I put the fluid drive on first. I cleaned it the best I could short of sand blasting. I was afraid sand would get inside. The chain and inner cork disk went on next.

Inner cork disk

This is the fixed middle disk that was missing. That meant that the inner and outer cork disks were rubbing against each other. They do not appear to be damaged.

Middle fixed disk

Next is the outer cork disk.

Outer cork disk

Now the outer fixed disk.

Outer fixed disk

Return springs and bolts.


Finally the clutch cover.


Fork installation

I would have liked to use both original kingpin bolts but I can’t since I had to drill and tap out the bottom mounting hole on the fishmouth to 9/16-18 UNF. Both of the original bolts were made from 5/8″ hex head bolts. They both have a center drill hole on one end which means they were modified in a lathe using a tailstock. The top bolt is drilled for safety wire and was centered on the hex end and the bottom bolt was centered on the threaded end.

I like the bottom bolt better since it has longer threads. I will use this bolt in the top but it has a few problems.

First it was not fully threaded which means it had locked up on the threads instead of the 5/8″ diameter shoulder. I suspect this was a contributing factor into how badly the bottom hole was messed up. I used a 1/2-20 UNF die to cut threads up to the shoulder.

The next issue to address is that the shoulder is not long enough to allow the bolt to seat on it. The bolt hex will lock up on the bushing instead. This will unloosen the bolt when you turn the handlebars to the left. It will tighten when you turn to the right. No problem as long as you plan all your rides using right turns only.

I used my toy lathe to make the shoulder longer by turning about 1/32″ off the bottom of the hex.

The next issue is that this kingpin was made from a 5/8″ hex head bolt that measures .611″ under the hex. This is too loose in a .625″ ID bushing so I decided to bore out a FB912-6 562″ ID diameter bushing to .612″ in my toy lathe.

Perfect fit!!!


Since the Albion is working correctly I decided to not rebuild it at this time. I cleaned it up on my Scotchbrite wheel and tightened up the bolts. It is leaking at the kick start and input shaft so I will keep an eye on the fluid level. There is nothing weird about it. We have seen plenty of these handclutch units before. I will detail the clutch sometime soon.