Helping HEQ mechanic on 5 series. Starter is not smooth. Seem to buck and kick. My feeling was timing. Proved it by disconnecting ignition. Turned over fine. Set timing after TDC and starts OK. When checkin with timing light mark seems to jump around. Removed distibutor and replaced vacuum advance. Everything the same. 2 questions, any ideas on why timing changed ? Is timing set with vacuum advance hooked up or not. Looks like vacuum source is above throtle plate so should get little or no vacuum at idle. Any thoughts ??