The road less travelled!
I don't think there are too many people on here (or anywhere else) using CCMs for overlanding so experience may be a bit thin on the ground. Chris of Motocross Africa set off to do UK to Cape Town and back on one of the smaller 404DS's but he hasn't updated his blog for a while so I've no idea how things are going / went. If anyone else has current information perhaps they could post it in this thread.
I have one of the older Rotax engined CCMs which I bought nearly three years ago to replace a Honda XR600. You may have come across some of my older posts about it. The Suzuki engines replaced the Rotax in 2001 but other than that the bikes remained much the same.
I bought it because I thought it had the makings of a good overlanding bike. The core bits of the bike - frame, suspension, wheels, brakes etc looked good and I thought that the other bits could be changed to suit my needs. I come from the old school of biking where oil under the fingernails and a spanner in the back pocket is normal so tearing most of the bike to bits and making parts that I couldn't buy is normal practice. With that in mind this is my considered assessment of the CCM:
1. They are of variable quality. I've been lucky, mine has been reliable in the sense that it hasn't stranded me at the side of the road but you need to be prepared to fix / remake things that other manufacturers would never release. I've had to remake the silencer mounts (about four times!), the lock stops and the tank mounts. The carburation on the Rotax engine is dreadful but that shouldn't affect the Suzuki. Others have not been so lucky and you frequently get four letter word comments about them.
2. They are pretty solid. The subframe is detachable and easily reinforced although I haven't had to make any alterations in this area. Unfortunately solid = heavy. They are not in the GS range but compared to the XR the CCM has tank like qualities. The seat height is the usual sky high trailie particularly if you have the seat rebuilt even higher (which you will - the stock one is second only to a DRZ400 for its numbing quality) but that shouldn't be a problem for you at 6' 6".
3. Nobody makes bits for them. Most of CCM's 644 production was of the supermoto version and there are some bits to bling up these but that's not much help. Tanks and luggage are the main problem. The std DS tank is 13 litres and that gives a range of around 160 miles. There are some 23L ex Paris Dakar tanks around but they are very very rare and you'd be better to see if something else will fit. When I was trying to do this I didn't find most of the usual suspects very helpful. You would need some pretty detailed measurements, particularly for the gap in the middle where the tank goes over the frame. I got lucky and managed to get one of the PD tanks but I can tell you that Acerbis XR tanks are much too narrow!
Luggage is going to have to be DIY so you'll have to be handy with a welding torch - or left to someone like Overland Solutions. Mine is DIY (and looks it!)
4. They are pretty cheap to buy and pretty difficult to sell. Based on what I've read on the CCM user group site the Suzuki engine seems to be good for about 25K miles before much goes wrong - as long as you don't convert to 710cc. The only other problem seemed to be the cylinder base gasket leaking oil on the earlier (02, 03) ones - fixed with a updated gasket.
Overall I've been pleased with mine. It is pretty crude but I like that. I don't have to worry about ruining something valuable and you do get a sense of involvement when you've improved some part of it or made a bit that you couldn't buy.