Finally made an accurate tool for timing my B31.
2 hours machining scrap pieces and now I can set the timing accurately in 5 minutes!
Machined a taper on 5mm AL flat bar, which matches the profile of the head fins. This piece pushes in, doesn't move during the timing, then is pulled out; easy peasy!
Bent up a left-over piece of 1/8" stainless rod (left-over from a knee lever added to a pedal steel guitar), and bent it with an approx 17mm offset. Consequently the rod touches the piston squarely, and the front part rises and falls vertically (in parallel).
A 1/8" slot in the front edge of the base allows the rod to be fitted into place after the Al base is positioned in the head (parallel with, and to the left of the spark plug hole). A graduated SS collared piece slides over the top of the rod. It has a grub screw so can be positioned, and locked in place when the piston is at TDC, and the bottom (first) mark on the collared piece lines up with the top edge of the brass guide bush.
There are 1/16" graduations marked along the SS collared piece; very easy with a digital readout on the lathe. Graduations go up to 1/2". Timing for the (hotted up) B31 is 7/16" BTDC; therefore the engine is rotated backwards until the second mark from the top lines up with the top edge of the brass guide bush.
Bike starts first kick, happy chappy!!
