A couple of things
You had the problem before you changed the discs, so its not the discs themselves.
The problem wasnt there when you first rode it, so what changed.
You haven’t mentioned changing the pads, are they contaminated?. Cleaning doesnt help.
Finally are we talking front brake, rear linked brake or both? (Are they still linked?)
Pulsing on the front end, new discs, pads ,pistons/seals at same time, new wheel bearings later, steering head bearings adjusted.
Calipers central to discs.
0.02mm runout not exceeded.
….. I completely follow your logic, as it follows mine, the only thing I can think is that shortly after buying the bike, I put a new tyre on it, so obviously removed and replaced the wheel, but I’ve been riding and fettling bikes for forty plus years, and find it hard to believe that I’ve ballsed up in that respect (although no one is infallible).
It’s a bugger
Planning on getting to the Scottish rally, so I can bend a few ears up there.
Thanks for the input
Also, as I mentioned previously, it’s easy to approach a problem like this with all guns blazing, and you can easily lose sight of the target through the gun smoke ( if you follow my drift).
But I cannot argue with your logic; that the issue was present before I changed discs and pads, and I need to keep that in my head.
Reading back through this, I can’t see mention of the possibility of an air leak? Is that possible? Could a small air leak, say, in the seals on the piston in the master Cylinder, or even down at the caliper end (seals, bleed valves?) - could that result in “pulsing” when braking? No idea, just “spit-balling” here.
See Mr.P’s question, too: Finally are we talking front brake, rear linked brake or both? (Are they still linked?)
My first reaction here is - caliper mounting shims/disk runout.
Does the bike still have linked brakes and a proportioning valve, if so, is the problem on the ‘front’ brake, or the ‘linked’ brake operated by the ‘rear’ brake lever, or both?
Still linked, don’t believe it to be self proportioning valve however.
Happens when using either hand or foot operated brakes.
Disc runout minimal, calipers central..
Very unlikely to be due to leakage of any sort.
Tbh, I’m going to give it a thorough review after next weekend…I’ve obviously missed something, I just wondered if there was some particular foible of setting up the front end, of which I was ignorant of…
Many thanks to all for offering assistance…I shall post any conclusions
here’s a clue. on linked brakes the hand brake operates the right front caliper. the foot brake operates the front left and rear. pulsing on both? maybe not the brakes at all then…
Exactly that Barry, if the brakes are still linked you should be able to isolate the problem to either the left or right disc, somewhat unlikely that both discs are similarly affected if it’s a brake problem, especially with the work performed to date.
If it still has a proportioning valve fitted it’s not clear to me how this could cause a pulsing effect, but worth checking anyway. Not sure how you check the valve is working correctly, so perhaps replace it with the simple (Le Mans type) splitter from the same era
Just wondering if it’s something to do with the newly fitted front tyre, either not fully seated or out of balance causing a once per rev ‘pulse’, possibly exacerbated when the front is loaded with braking.
Will be interesting to see what it was when finally fixed.
“Happens when using either hand or foot operated brakes”
This rules out quite a lot - hydraulics, discs and pads.
So we’re left with wheels, forks and steering.
I know you have adjusted head bearings but worn bearings can produce a chattering which could be described as pulsing, so I would try rocking the bike forward and backward with front brake firmly on and see if there is any slack or movement in the forks or bearings.
If the problem started after replacing the front tyre, that may be the cause, instead of the brakes. Try deflating and re-seating the tyre to the rim, using the moulded lines to ensure it is perfectly concentric on the rim (that’s why they’re there!). Then re-balance the wheel/tyre assembly.
Think you’re probably right in your thinking…replacing bearings was on my list, and adjusting them up has reduced the degree of pulsing. As everything else seems sound and within tolerance, I shall be doing the job shortly
One thing that can cause the disc to run out of true, is corrosion under the disc carriers where they attch to the wheel centres.
So, check bearings, maybe need renewing, also, have you checked / measured run-out of rim and tyre? Also possible, balance….. although tyres can be a bit uneven but still work OK without any apparent faults.
Who changed the tyre, if not you ‘they’ might have damaged the wheel somehow (note I’m assuming ‘you’ wouldn’t have done anything like that 
)