I need to extend my loom in order to connect to my bosch fuel pump (for an R1 injection engine) so need some cable but I do not have a clue about cable sizes and how to work out what thickness and amp size I need.

any help would be much appreciated

Depends on whether you want/need standard or the more modern thinwall cable. Best to stay with what your loom is made from I guess.

Thickness vs safe current rating's are on VWP's website.
Standard http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/standardcable.php
Thinwall http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/thinwall.php

Not sure how many amps the bosch pump draws, but look at the fuse rating for the fuel pump circuit. If you are using the MNR loom to power it then I think it is a 10 amp fuse, not sure what the bike fuse rating is. Choose a cable which can handle a bit more than the fuse rating.

thanks for the links and info

the loom is from MNR and does have a 10amp fuse so I now know what I need to order

thanks again