With the cylinder slanted rearward, air intake in front, and exhaust outback (where nature intended it to be, perhaps) and a virtual ram-air effect on a motocross bike, the new YZ450F certainly gets your attention. The details don't disappoint, either. The cylinder is slightly offset so that the connecting rod is vertical at the moment of combustion, thereby minimizing piston friction against the cylinder wall during the powerstroke. The four-valve, fuel injected engine sits in an entirely new "bilateral beam" frame that features a double S bend that purportedly improves handling.
No battery is necessary to power the fuel injection system with its 44mm Keihin throttle body and 12-hole injector spray. Yamaha claims the FI "provides optimal air/fuel mixtures in all altitudes and a wide range of temperatures for outstanding throttle response."
This new engine has a new bore and stroke (97mm x 60.8mm) and a higher 12.5:1 compression ratio.
Q:motorcycledaily.com
Kommentar