Having fitted a new rear brake lever to my bike I know find that it will not tighten up enough to stop the brake pedal moving under heavy pressure.Looking at the connecting part from the pedal to the brake rod at the rear of the frame which also has the adjusting part on it the splines are not in good condition and would really need to be replaced.I have posted a wanted add in the classifieds but would appreciate any help on the subject or how to rectify the problem.I can fit a return spring and adjuster but need the connecting part

I think you would get better answers if you posted in the "Honda" forum on this site.

I am not sure what you are exactly explaining but it sounds like the one (or a combination) of three problems:

1) The internal spline on the aluminum lever is stripped.

2) the external spline on the pivot shaft is stripped

3) the brake pads and or drum are worn and the pivot shaft is turning too far when spreading the brake shoes.

You are using a clamp bolt in the lever, right?

thanks for the info and am using the bolt it is the internal splines of the pivot shaft not the brake lever

Stripped spline can be really hard to fix. You might be able to sharpen them with a small triangular file than tighten the clamp bolt very tight to grip the lever onto the shaft. No guarantee this will work for long.

If you are handy, there is another possibility. You can cut a keyway into the shaft and a keyway into the lever and use a square woodruff key and still use the clamp bolt. Check Google images for "square woodruff key" for examples. This technique is used to index gears and flywheels because it is very strong. The drawback to this is you lose the ability to adjust the position of the lever to the shaft, so the only adjustment you will have is the knob on the pull shaft near the hub.

Best solution is replace the worn parts with good ones.