At my last renewal I looked at my bike and declared everything - I had to pay £375 I think (dread to think now, could have been more) but list was pretty long. Cannot remember which really pushed it over the edge - could have been bodywork or quick shifter - decided to declare the lot just in case. However, none of it is actually covered - bike is standard replacement parts only . BUT... if you don't declare and there is a claim its grounds to refuse to pay / accept claim
Power Commander will probably be the most policy loading item I would have thought, and yes always declare everything even if you do only receive the standard items as replacement if the worst should happen. I am involved with insurance assessors and often a quick look over the bike with a few pictures and a check of the tyre tread depth (sometimes) is all that happens, however if you were to be involved in a serious incident then I expect they would dig deeper. I've had bikes with exhausts, levers, screens, PC's fitted that have not been noted/noticed but I certainly wouldn't chance it.
Absolutely, declare any extras, they are only looking for an excuse not to pay out in the event of a claim, so by saying nothing you may just as well be un insured.
if you get a quote on ebike website for a standard bike , you can use the "back" button on their website and add the mods one at a time to the quote,then go to the new quote and see how much difference each one makes. After all it is only you enquiring how much difference it makes if you should decide to buy and fit parts. ahem.
I have told Carole Nash everything and it didnt load the price at all, but as Mr B said, things like power commanders and such like might cost more. Carole Nash didnt even seem bothered by my exhaust ! go figure that one out.