I have 3 Toro Proline 21" WB's. Bought all three new. After about a year they start rattling and I notice some loss of power. I am using Amsoil 100:1 ( I searched the threads and hear that advice but I have been using 100:1 since the units were new.) Any advise? Has anyone torn down one of these suzuki's and cleaned out the head? Thanks for your help.