Hi RoyC,
Thank you for your feedback.
I acknowledge and apologise for the issue about the slot which you had to file out, the one you show in the photo is not deep enough. It aligns with a peg in the magneto, and these pegs seem to be all over the place, some protrude a lot more than others. The slot is fine for the magnetos we have here, but obviously was not deep enough for yours. It is a manufacturing error on our part, as we normally make them deeper to allow for the variation in the magneto bodies mentioned. We have sold thousands of kits for the Lucas K2F, and I can assure you that your experience of having the file a bit off is not what normally happens.
You also say you made up a plastic washer because the fuse blew. This is not necessary, the kits are designed to work without such a washer. The fuse blows because there is something in the magneto protruding and touching the unit, which shouldn't be there. The answer is to have a look and find out what is touching it, and to sort it out.
I note that you mention that you stripped the unit down and re-assembled it, I would guess it is probably something to do with that which has caused the fuse to blow. If it is now working with the washer you have put in, then it will not do any harm!
Regarding the ignition timing method you have used, we would not recommend it. It is extremely inaccurate, not to say almost hit and miss, and if it has resulted in accurate ignition timing for you then you have been very lucky. I note that you have manual ignition advance, so if the timing is out you have the option of altering it manually as you use the bike, so there is leeway for error. If you have automatic advance, then it has to be set correctly. The A10 is almost a modern bike, with quite high compression and rpm, so by setting the ignition timing properly, as per the instructions with the Thorspark kit, it will run properly and pay dividends for the extra work in the long run.
You also say that your bike is now running great. There is normally a marked improvement in running after fitting the ignition kit, so it may feel like it is running very well, compared to the previous tired magneto, but if you set the timing up properly, it may well run better still!