You don't time a 60" Haban. Blades should be 21" long.
This is from the Oregon catalog
21" long 1/2" center hole 2" wide 1/4" thick
759-3411 Cub #
759-3839 Cub #
91-442 Oregon #
Probably not your problem but I bought a Haban once that the owner said it didn't cut very well, it had one blade on upside down.
They also don't like wet grass, check for buildup.