2200kv sounds a little sick

[kneedeeppow]

my truggy has been out of action lately due to esc meltdown castle have been awesome as per usual while i was esc'less i lent my 2200kv to a friend who had it running in his losi. at ran fine in that. upon rebuilding by truggy in readiness to wire up the replacement esc i noticed when freewheeling the chassis along the ground the motor sounded really clunky(alot more than they normally do) i havent put the esc in yet,dont want to vaporise the motor and or esc.
any ideas on what could cause the excessive noise? (i know its probably a silly question)