I'm having an issue with timing my 75' 750. The timing advances smoothly on both 1&4 and 2&3. It stops right between the advance lines. However, if I rev it up to around 3500 rpms the timing jumps forward a few degrees and than back to the advance marks on 1&4. It keeps jumping back and forth but is mostly over advanced. This isn't a smooth movement like normal advance and doesn't occur on 2&3. Is my advancer bad?
