Comic Jay Leno is a proud owner of one of these great Allison aircraft/marine style jet turbine motorcycles produced by Marine Turbine Technologies. These bikes cost a cool $150,000. The Allison R-R 250 C18 engines weigh just 136 pounds, yet produce an awesome 317 horsepower and 425 foot pounds of torque. Part of the advantage of turbine engines is that they continually produce power, unlike the sequential power process of comparable four stroke engines or even of two stroke engines, which have superior power characteristics compared to the four stroke engines of the same size.
Part of the disadvantages of both turbine engines and of two stroke engines, is that in producing so much power compared to four stroke engines, they are more wasteful of fuel and tend to produce higher pollution levels and often are far more noisy in operation. Four stroke engines can be civilized down to a level where emissions can be greatly reduced and pollution control devices used. However, that becomes more difficult in either two stroke or turbine engines because of their power producing characteristics.
Turbine engines also tend to spin at outrageous numbers of rpms compared to comparable two and four stroke engines as well. In the early 60's, Chrysler Corporation built a small fleet of experimental gas turbine powered automobiles which strangely sounded like giant vacuum cleaners when running, but were very powerful, but produced a great deal of heat and also burnt a lot of fuel compared to comparable conventional automobiles. And the engines tended to spin around at up to 50,000 rpm, forcing Chrysler to greatly gear down these engines for safe street use and manageability.
For racing applications, turbines always have great potential. However, with the wild power they produce, greater pollution levels, and sometimes very noise levels, gas turbines are not very practical it seems. But they sure are cool!