More information required before any specific assistance or advice can be provided. Which model of "BMW Motorcycles Navigator Garmin 2004" is it? If its simply called BMW Motorrad Navigator without a series number, then it's the very first model. if so, like the II, III and IIIPlus, Garmin claims that it cannot handle map updates:
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But Garmin often isn't completely truthful about its older unsupported devices and there may be a workaround to load partial EU mapping data to it.

Also i guess by 'navtech charts' you mean NAVTEQ maps do you? The Navtech company (now Navblue) specialises in air management systems and aeronautical enroute/airport navigation charts - whereas NAVTEQ has been known as HERE for some many years now. If it still has NAVTEQ mapping loaded it must be long overdue for map data updates for sure.

Post some pictures of the device, along with the additional information including which countries' maps are presently loaded. Use 'spoiler tags' for large images, read here: [Only registered and activated users can see links. ].