"Since Reliant 3-Wheelers were mentioned. I'll say this. I've owned 4 of them. I had a Haynes Manual for them. If you ignored the timing fault (The Manual said that the timing was at TDC, not 10 Degrees BTDC), the Manual was pretty good."
The Haynes manual also tells you to rotate the distributor anti-clockwise to advance the ignition timing - it's clockwise. Those two errors have confused many a DIY man and resulted in many under performing Reliants.
Although I still have the manual on my shelf, I would like it to go on record that I only owned a Reliant three wheeler to use as a donor car for my Liege 4 wheeler

I had it delivered, drove it 100 yards up our private road to check everything worked as advertised, then it was dismantled.
Built like a gun... could go BANG!