The idea of a diesel motorcycle is one we like a lot around here, the Thunder Star 1200 is a long time favorite, the Neander is pretty interesting, too. While some of these companies have been working on putting a diesel in a motorcycle frame for years, it seems like it’s taking forever to actually get one on the road. The Neander is finally for sale, the Thunder Star still sits. There are some really old slow movers like the Royal Enfields but, that’s another story.
While all of this development work has been going on, the fuel supply and price situation has been steadily changing and the emissions regulations are getting tighter. Diesel now costs more, sometimes a lot more, than gasoline. Regulations covering particulate emissions are really tight and after treatment of diesel exhaust is getting complex and expensive.
PSA Peugeot Citroen, one of the leaders in European diesel engines, is changing course and developing a new gasoline engine to meet the new Euro 5 and Euro 6 emissions standards. Diesel is big in Europe but if a major manufacturer of diesel engines sees diesels as too expensive to keep clean enough for the new standards, there may be a problem looming for the small displacement diesel market and that is where any diesel motorcycle would fit in.
Diesel engines in motorcycles were never going to be a big market but it was an interesting possibility. It looks like those endless development cycles may have killed them before they got a chance to get moving.
UPDATE: I forgot about the HDT Bulldog, too, which Chris mentions in the first comment. Thanks for the reminder, Chris.