I suppose the battery and points go to earth on the engine anyway on the traditional system. Just never needed to consider it since college over 50 years ago.
New spark plugs and new HT leads had no effect on the problem. A new coil made it very slightly better. It will barely run above idle where before it wouldn't run at all above idle. It idles really well though.
What do you think the reddish brown deposit in the float bowl is, it must be fine if you have a good paper filter in the system.
Just a thought , the deposit isn't magnetic as in fine rust dust particles, could that get on the porcelain insulator as a deposit near the electrodes of the spark plugs causing a misfire. Though didn't one plug run cleaner than the other?
I cleaned it all out the other day and didn't test it. I just discovered the photo so I thought I'd post it.Is it ferrous (ie will a magnet pick it up)?
I had one briefly but was advised to remove it. I might refit it up at the front.If it's from the tank it will return.
I forget, did you have a paper element fuel filter?