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Points backplate positioning.

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SteadyEddie:
Dragged the CB750 out of the shed today for the first time in over a year, I have never been able to ignition time 1 and 4 unless the backing plate is turned so far around the screw holes do not line up on the two lower screws ?

I have removed the backing plate and as far as I can tell it can only go in one set position in realation to the points cam lobe due to the dowel on the advance and retard mechanism.

Any ideas ? or am I being really thick ?

The red arrow on the image shows how far out the screw hole is.

hairygit:
 Put the points plate roughly in the middle of the screw slots (move it anti clockwise) then rotate the crankshaft until the first set of points is open to its widest (ignore the "T" and "F" marks on the advance/retard for the moment) Adjust the gap of the first set of points to specification (15 thou seems to work best with imperial feeler gauges) then rotate the crank until the other set of points is at its maximum opening, and again set the gap to spec. Then you can set about timing, using "F"1.4 for points marked 1.4 the points plate is rotated very slowly until the points just begin to open (NOT fully open) When you have done this,tighten the base plate screws, then rotate the crankshaft to the "F"2.3 position and do the same with the points marked 2.3,(only make adjustments with the small sub plate they are mounted on), then all should be well. I assume you have checked the condition of the points? not just the contacts, but also the plastic/fibre heel that rubs on the cam? if the heel becomes badly worn,accurate timing can be very difficult to achieve

SteadyEddie:
Thanks for the input Hairy, I will have another go on my next rest days.

Points are new.

SteveD CB500K0:
A 12 V light bulb and some wire is good for checking the exact opening point of the points.

Lamp on = points open
Lamp off = points closed

An essential part of my toolkit for the last 35 years!

Spitfire:
Yep, a bulb, a battery and a couple of crocodile clips is all I ever use as well.

Cheers

Den

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