Sigma advertise the service, and I am sure that Pro-Twins will do it too.
The 'traditional' and cheaper-in-parts way is to use offset keys, but they are limited to a few degrees.
http://www.moto-one.com.au/performance/index.html I have been warned off the vee-two vernier pulleys that sigma advertise by tales of failures, but I am sure some of those could be due to inexperience in setting up vernier pulleys. Vernier pulleys are much more expensive in cost terms, but much faster and easier to set up.
Dialling in the cams is one of the key things in the sigma 'full-monty'.
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