Points backplate positioning.

[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

[SteadyEddie]

I use the lamp, well the indicator off the bike wired up, works a treat.

[SteveD CB500K0]

  Mine's an old indicator lamp too.

I don't use a battery though Den, just the ignition on the bike.

[mickwinf]

i use an old instrument illuminating bulb off a speedo so it has a nice rubber insulated holder!

[Bryanj]

I nick Borrow Daf side marker light bulb holders from the workshop along with 2 tiny spades and use a 12volt capless bulb and croc clips on the 2 core wire (also borrowed)

[SteadyEddie]

All sorted,
Hairygit sent me a PM detailing how to go back to basics on set up and all is now well, she fires on four cylinders a treat. Bit of carb fettling now required.

Think I am going to plump for the F tank instead of the K tank.

[SteveD CB500K0]

Have you seen DME's tank?



http://forums.sohc4.net/index.php?topic=40417.0

[SteadyEddie]

Yes I have seen that before, but i am a bit reluctant to cut up the early "K"series  right hand tap tank that I have, the "F" series tank was cheap and cheerfull so i won't mind having a go at making it longer as in my dodgy artists impression.

[hairygit]

If the F tank doesn't leak, hang on to it, they are difficult to find in usable condition, there are far more K series tanks out there, and even replica ones, but F tanks that dont leak are VERY scarce!