one of the best tools you can buy for tasks like that is a hot air gun, you can pick them up these days for a tenner and should last a while. use it to heat up around the alloy casing where bearings sit, get it good and hot and use a mallet to knock the casing. most manuals will show a purpose made puller but those cost money and you will probably never use it again. hope this helps.
ye iv got a hot air gun will try that. iv seen this on ebay will this work http://cgi.ebay.co.uk/ws/eBayISAPI....6528195&ssPageName=STRK:MEWAX:IT#ht_500wt_715
yeah, before re-assembling, put the crank/bearings in the freezer and heat up your cases again. with this you will be well suprised how easy it will all go together.