There are a couple of Mk1 ignitions To start with this is for the later Mk1 type ignition barrel
Like the Mk2 ignition the barrel on this one is retained in the body by a spring, the only problem is that unlike the Mk2 there is no predrilled hole to depress the spring. So we need to drill one.
Lay the ignition numbers side up and mark up a point 15mm down from the key end in a line with the point the casting becomes flush at the bottom.
Drill a small pilot hole then drill a 3mm hole, don’t push on to hard as you need to stop just as it pops through the body so not to damage the spring on the other side.
Turn the key to position 1 then insert a small screwdriver into the drilled hole to depress the spring and at the same time pull on the key to pull the barrel out with the switch actuator still attached.
When you remove the barrel be carful not to loose the dowel pin and spring at the bottom of the barrel recess, the barrel just pulls of the actuator but again be carful of the spring and dowel pin holding them together.
To refit the barrel click the barrel back on the actuator make sure the dowel pin is in the correct position at the bottom, Select position 0 with the key then slide the barrel back into the body while aligning with the slot in the body.
Push the barrel in and help the actuator through the hole at the bottom then push until the barrel is flush with the ignition body, and your done!