#1. "RE: 1970 commando timed breather" In response to Reply # 0
The breather should be hooked up. It is a bit undersized for the 750 since it's design originated as a 500cc. Even though it is better than no breather at all. The timing disc will help if you have low blow by. If your engine is pooped out, leaving the disc out may not be enough to over come the excess flow. Engine bottom end pressurization is the result along with oil leaks.