How did Japanese companies come to dominate the "crotchrocket" segment of the motorcycle market? How, when and why did these motorcycles first become popular in America?

First off, a caveat: I'm a brit so a lot of what I know about the motorcycle industry is biased in that direction as I simply know a lot more about the British motorcycle industry than those of other countries. There's an interesting book called Whatever Happened to the British Motor Cycle Industry? by Hopwood and Wilson that's worth reading for an insight in to what was happening in the 60s and 70s. Hopwood doesn't miss an opportunity to grind his axe against people he thinks were to blame for what happened and I took those bits with a big pinch of salt. As an account of what was happening in the market, though, it's worthwhile.

In the 50s and 60s there was a huge number of motorcycle manufacturers. The "high-performance" end of the market was arguably dominated by British bikes - Norton, Triumph and BSA won a lot of races and that fuelled sales. There were other manufacturers vying for this end of the market as well - Harley was doing very well in flat-track, BMW and NSU was very competitive in some areas etc. Nevertheless, British bikes were seen by many as the sports bike of choice.

The problem was that, as fantastic as Triumphs, Nortons etc were in the 1950s, by the end of the 1960s they were still selling what were pretty much the same 1950s bikes. The Norton Commando that was introduced in 1967 had an engine design that dated back to the Norton Dominator on the 1940s. Triumph's engines were at least a bit more advanced but their rolling chassis were awful. This was what gave rise to the popularity of the "Triton" - a Triumph engine in a Norton frame - and similar swaps.

Meanwhile, in the 1960s Honda was successfully selling huge numbers of small bikes, particularly in the US, by marketing them as friendly and fun. This was in contrast with larger bikes that many people associated with motorcycle gangs (movies such as The Wild One, Hell's Angels on Wheels and Wild Angels didn't help). Other Japanese motorcycle companies were also doing well in the small bike market and also producing some race bikes but were not seen as real competition for "proper", big bikes.

Then Honda announced the CB750. It's hard to understand how revolutionary that bike was at the time. It had the same kind of impact on the market as the original Honda FireBlade or the BMW S1000RR did - it was a substantial advance in technology and instantly became the benchmark against which all other bikes were compared. It had four cylinders, disc brakes, reliable electric start and was faster than any other mass-production bike. At first it was treated with some suspicion as Honda didn't have any kind of track record for a bike like that but it proved itself as relatively reliable and, well, easy. It was far from uncommon for keen bikers of the time to routinely ride their Triumphs or Nortons over the summer and then do an engine rebuild over the winter. The CB750 didn't need that. It just worked. The CB750 was the first of the super-bikes and it was enormously successful.

The success of the CB750 spurred other Japanese motorcycle companies to build bigger bikes. The Kawasaki Z1 was everything the CB750 was but more so - faster, louder, sexier. These flagship bikes helped draw attention to the Japanese manufacturers which helped their sales of smaller machines as well. Four cylinder bikes were the new hotness.

While all this was going on the British motorcycle industry still kept cranking out pretty much the same old bikes while their sales figures dropped through the floor and industrial action hit the manufacturing plants. BMW was also quite conservative but they did at least make sure that their bikes worked and were reliable. Bikes such as the Norton Commando had had their old engine design stretched so far that it was not a matter of "if" it was going to suffer catastrophic engine failure, merely a matter of "when".

In the US, Harley Davidson was also struggling hugely. It was bought out by AMF at the end of the 60s and underwent painful restructuring that led to strikes and a drop in quality.

The British motorcycle industry was effectively dead by the end of the 70s. Harley was a fraction of its former self and suffering from a very poor reputation. BMW had evolved into its niche of expensive but reliable sports-tourers and Ducati was still just about hanging on doing its own exotica thing.

By the beginning of the 1980s the Japanese manufacturers dominated the market with a huge number of cheap, powerful, (mostly) reliable and high-performance bikes. The sales that the Japanese manufacturers were gaining allowed them to put a lot of money into R&D to keep ahead of the game so it ended up as an arms race amongst the big four (Honda, Kawasaki, Suzuki, Yamaha) to produce the next biggest/fastest/most wow bike. In that kind of market it's difficult for a new starter to gain a foothold.