- Apr 18, 2000
this happened to my brothers yz400f. he started it up and let it warm up for a minute, then shut it off and put on his race gear. he restarted the bike and took off to do a slow lap (2nd gear maybe 1/3 throttle) and check out the track. half way around the track the bike locked up. he pushed back to the truck, went home and started to tear down the engine. the rod had broken about an inch below the pin. then went down with the crank, but when it came back up, it fell forward, missed the cylinder and went through both halfs of the engine case at the front motor mount. has this happened to anyone else? why did the rod brake? it was not even under a hard load at all. the rod looks good otherwise. no discoloring like it had ever become too hot. the bike is into its third year, but has very low time compared to some of my friends who ride theirs alot more. it has had the top done about a year ago. any ideas?