From a mechanics point of view..... Bulletproof. A company that I worked for looked after 15 BK117's (A4/B1/B2), and in the 3 years I was there, they never did any unscheduled maint on the MGB. I did the Mast Spacer inspections for the company, and that would have to be the weak point, especially if you do alot of heavy lifting work with your BK, just about guaranteed to be replacing the Mast Spacer during the inspection due to wear. Keep on top of corrosion and paint condition. That magnesium sure does fizz when salty air gets on it!! The quality of the gears inside is very good. After 5000 hours, they usually look like they are new. It is surprising that the MD900 series has problems with a Kawasaki gearbox. The BK MGB's are built very well, and just keep going and going. Did you know that Kawasaki also do the inputs for the AB139 MGB?
noooby