Thanks for the info, I'll try what you've said and report back, but does this mean that any revised mapping, ie altered road junctions, new roads etc are not easily downloadable to the motorrad nav 111as the regions I'm trying to update are the regions already installed on the garmin. By the way I rang garmin with the problem and they didn't seem interested.
Changes aren't loaded individually, it's a complete replacement of the existing installed mapping on the unit. These cannot be loaded on a revision by revision basis.
If you saved just one mapping tile in Mapsource as your gmapsupp.img file, renamed this to gmapprom.img and loaded it by using one of the methods described above you would only have that tile loaded on your GPS. In other words making a change to the mapping will overwrite all primary mapping that's already on the GPS. The same can be said for the secondary mapping, each load of this via Mapsource onto the device will overwrite the previous gmapsupp.img file. Loading routes and custom waypoints (favourites) from Mapsource is different, these do not overwrite the previously loaded routes and waypoints but add to them.
The primary mapping and secondary mapping are independent of each other though the memory for supplementary mapping is basically what's left over once the primary mapping is loaded. Sure you could load parts of your new mapping upgrade into the remaining 600MB or so of space but as your new map set is about 1.4GB it's plain to see that not all of it will fit on. Mapsource only tells you this once it's tried to load the mapping and taken an age to do so.
It is important that you reduce your secondary mapping to a negligible size before doing a primary mapping update. If your primary mapping memory is full and the update is bigger than the previous primary mapping install (they always tend to be) then there will be a clash and the update will fail.
A better alternative to Mapsource for loading supplementary mapping is to use
Garmin Mapinstall, this will report on the available memory on your GPS so you can make a call on how many mapping tiles to load. This is the way I managed the mapping on my 2720 before I found out that I could replace the primary mapping using the techniques described in the SmellyBiker link in my previous post. I had the redundant US mapping as primary taking the lions share of the total memory and loaded parts of Europe into the supplementary memory as I needed them. Obviously this wasn't ideal, I preferred to have all of Europe installed as on the European model. Garmin, despite selling me the European mapping, said that it wasn't possible to replace the US mapping with European and I would have to load it into the supplementary memory space.
The hacks I describe are not for the faint hearted, whilst I'm sure they are not approved for public use by Garmin they wrote the software that is used. The command line stuff is there for them to use to do stuff that the end consumer isn't made aware of. The risks are low but there is a slim chance you could turn your GPS into an expensive paperweight. Even a failed update, I'm sure, can be recovered from. If you are not able to save the pre installed gmapprom.img file from your device overwriting it will erase it and it'll be gone for ever, no going back...
Please also note that the methods described will not circumnavigate (pun not intended) the unlock code. You must have a valid unlock code, purchased from Garmin, for the mapping
and specific GPS unit your are upgrading installed in Mapsource. Failure to do this will result in the GPS unit not recognising the mapping and you will have wasted your time.