Sorted the bottom end misfire on the Tiger 750. Spent an hour last night understanding the timing marks on the alternator rotor (on the end of the crank), and finding the timing notches on the flywheel (one at TDC and the other at 38 degrees BTDC), and checking these with a screwdriver down the plughole in No. 1 cylinder, and making sure that at 38 degrees BTDC the piston was 0.415" lower than it was at TDC, as it's supposed to be. So that's all good. Need to check all this because good old Triumph, in the dying days of our motorcycle industry, were apparently a bit inconsistent in what bits they fitted, some have 2 timing notches, some only one, and it could be either one. Hence the need to check what you are seeing.
This morning, now it's stopped raining, rolled the bike outside, fired it up and let it warm up. Checked the timing marks with my new strobe. A bit out. Turned the coil sensor plate in the timing one way a bit - worse. Turned it the other way a bit. Spot on.
Rode around the block. 5 miles. Bottom end misfire gone. Much smoother too. And all without charcoal biscuits or a Brita filter. But thx for the suggestions.
And thanks to the internet for supplying loads of info on how to do the above. 35 years ago when I last timed a motorcycle engine, it was all done with a Haynes manual, and sometimes they were right, and sometimes they even showed you how to do it. Sometimes.