2 things... DECLARE THE MODS
Some will not charge extra but will only replace the parts with standard items (as mine will) in the event of damage/theft. i.e. you put bling on, fine, but if it gets nicked don't expect anything extra. The exception is for "performance" modifications, i.e. exhausts/filter/tuning usually with more than 5% increase in bhp.
This is more likely to increase a premium. Better to pay a bit more though than have them worm out of a claim because you insured a standard bike and the one that's stuck in a hedge after smashing into a Bentley has some carbon bits on
As for the chain, check if you get a reduced premium. If not, or if it's neglible DO NOT DECLARE it. I declared an Almax chain, and the small print said any claim would be invalid if the listed security devices were not fitted at the time of theft. When I called up, they took it off the policy and the premium was the same
Hope this helps