2013 xp 900 with 500 miles has what sounds like a loose rocker arm noise at start up...the noise only lasts for about 2 seconds and then all is quiet, and it only happens when it hasn't been started in a couple of weeks...if you start it up everyday or so there is no noise...is oil leaking back down away from the rockers and they are dry on startup?...any ideas on what it is and if it could be a problem....thanks in advance...