Hi All,
Having ridden Freetown, Monrovia, CDI, Accra in 2014 I'm wondering why they were refused entry. There were border closures during the Ebola crisis but both countries have been declared Ebola free a couple of times now. There is the option of trucking across the border but that won't help you if the reason why they couldn't enter was due to visa problems.

Also slightly off topic, there are major shipping companies who use Freetown Container Terminal which is now managed by Bolloré Logistics. I used to work at the port and can confirm that at least one roll on roll off ship arrives every couple of weeks delivering second hand cars all along the West African coast. Not recommended for the OP unless in a container.

Kenya Airways flys from Freetown to Nairobi via Accra. They may take a bike, but as PanEuropean says it depends on the equipment they use.

This is the first time I have heard of this happening and I lived in SL for 4 years. Unfortunately I left in December of last year so I can't offer more than my opinion at the moment. Please update us when you receive more info and I might be able to recommend something. There is a small bike community there in SL, but most people are expat workers like me and we tend to get contracts in other countries and disappear.

By the way, the easiest place to get a Nigerian visa is Abidjan (if you are a non resident) so I recommend to get across the border somehow rather than fly over CDI. If your buddies have not secured a Nigerian visa yet they may have mega-problems east of CDI. In my experience each embassy told me to get it in the next country which resulted in a dead-end. YMMV.
Cam.