MK0 vs MK1 Handlebar Comparison

I believe the handlebars are from a BSA Bantam D1 and D3. They are still available new but the brazed on perches are a bit different on the new ones. MK0 on the right, MK1 on the left.

Both my MK1s and the MK0 have the same bars with English Doherty grips and twist throttle. I put a wider Aluminum bar on the Rust Bucket MK1 because I was riding it daily for awhile and the narrow BSA bars beat me up too much. I am trying to find a chrome plating shop. Eventually I want to get the Rust Bucket MK1 back to original.

More MK0/MK1 handlebar pics.

The kill switch is drilled and tapped on the left side of the MK0 bar and the same kill switch is clamped the right side of the MK1 bar.

Parking Brake

I know this is not original but I install parking brakes on all of our bikes due to the steep terrain we ride on. I first saw an improvised parking brake on a barn find MK4 auto bike about 15 years ago. I was able to identify it as an exhaust hanger o-ring from a Volvo P1800 2 seat sports car. The P1800 was built from 1961 to 1973 so at least the o-ring is period correct.

I store the o-ring on the left side since it falls off on the right side due to the throttle cable. The left side has the clutch lever. The brake lever is on the right.

I have been using these on our MK1s for years. The MK1s have the brake lever on the left. This really screws me up when I jump off the MK1 and onto the MK0.

I can store it on the left side with the brake lever on the MK1s.

I use a Yamahaha quad parking brake on our MK3 and MK4 bikes.

I retrofit the Yamahaha parking brake trinket to the original Magura brake lever on my MK8 bike.

U-joint installed

The u-joints were both worn out in my MK1s so this is the first functional example of an early u-joint I have come across. It has a grease fitting that is accessible through the fishmouth.

Here is the patent drawing showing the u-joint.

My collection of junk early u-joints. 2 came from my MK1s. Not sure how I got 2 more. None have provision for a grease fitting.

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 1.00. 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 1.00…… 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 1.00 tap shows up. The adjuster now allows me to get full throttle on the scooter.