Clunking from cassette/free wheel

[norkmeister]

I have a newish kit, only about 250 km on it.  When I pedal there is an intermittent clunking from the rear cassette.  If a free wheel for half a second I can usually find a different position on the cassette where this doesn't happen.  Investigation with the bike upside down in my workshop reveals that the free wheel or the hub is not true at least in relation to one another.

Has anyone else had this problem?

Is the rear cassette readily replaceable?  A bike shop told me it is non-standard, so where would I find one outside of ordering a replacement from GM?

Thanks in advance for replies.
Jeremy
http://ebike2work.blogspot.com/

[karma]

yes I had the same problem my cluster would wobble and it was loud, you can replace it with a better one.
you will need a hammer a flathead screwdriver to remove the lockring on the front of the cluster, than pull it apart
and use a pipe rench to remove the rest. I have a pic but the forum folder is full


http://www.bikeforums.net/showthread.php?t=326941&page=3

its nice all I can hear now is my hubmotor, and not the loud click click click the included cluster is a freebee anyway and its junk along with the included rim