heres a few thing o try. Take achain apart the small cicrullar rings that are inbetween links are the perfect sized spacers just need a few of them. And also i had this hppen to me, i went to a local mototrbike secialist to get mine done and he explained that if you are using steel (bolts) and alu frame or visa versa they have a small reaction which causes the threads to weaken and thus strip but if you use copper grease which is like £4.50 from halfords it helps to prevent the reaction by causing a small barrier and protecting the threads.. Tom