The clutch release fork may not have sufficient strength, because its keyway is not properly processed and causes localized stress, and therefore the fork may crack after repeated clutch operations. If the vehicle continues to be driven with the cracked fork, in the worst case, the fork could break, in which case it would become impossible to change gear with clutch operation and the vehicle would stall. Also, the fork may crack due to improper maintenance, such as applying grease of the wrong type, and this could result in the same problem.