I have rebuilt several primary units in the past making this one pretty straight forward. One issue encountered has been torquing down the spindle nuts without spinning the rear wheel. To head this off the cylinder was left off and a steel rod was put through the connecting rod small end bearings to keep the engine from turning over. This also worked well for the transmission & timing gear assembly.
The primary was shot on this bike. One of the inspection plugs was left out and covered, somewhat, with tape. The primary had a lot of dirt in it as a result. A used primary was purchased from the same seller on ebay that sold the transmission to me. I installed new seals, rubber buffers, and fiber plates in the clutch. An old BSA dealer told me that Emgo plates do not stick as bad as Barnette plates, which I have had issues with. Since I will not ride this bike hard I went with the Emgo plates. The steel plates checked out flat on a surface plate and are being reused. While I had it apart I also filed the burrs off of the clutch basket. They were not very big but cleaning them up should facilitate smooth clutch plate movement. Once the pulleys were fit I checked sprocket alignment with a depth guage.
The primary chain had also run out of adjustment. To make up for this a previous owner had welded a lug nut under the adjuster, which can be seen the photo above. The down side to this is that the chain had slapped against the case and worn groves into it. They look bad but no significant damage had been done.
Primary assembled except for the clutch springs and pressure plate.
An Emgo fiber plate with a factory steel plate.
The ET ignition system is going away on this hornet. While putting on the rotor I found it was mounted to a plate with location holes in it. It seems this is an adjustment for ignition advance with the ET system. I turned the spacer plate around which put the pin to the inside of the bike and then located the rotor with the key. I also put a stator from a 1970 thunderbolt on the bike. I am not sure if the ET stator would have worked with standard coils. The stator wires were cracked which was rectified this with “liquid tape”, a pointer from a friend in Idaho. Thanks!