10-08-2019, 10:44 AM
It sounds as though it is firing as you approach tdc. In my experience when a Ruby type engine is running well you probably will have this situation if turning the handle slowly. When you swing it briskly on the handle it will not be noticeable unless you have it over-advanced. The sound of the engine running will probably be rougher in that situation. Smooth running is always preferable. By blipping the throttle as you adjust the timing you should be able to judge the right setting.
Robert Leigh
Robert Leigh