Looking to put the barrels on the 750 Fastback rebuild now. +20 re-bore. Hepolite rings. Rings were already on the pistons when I purchased them. As with rebuilds on other bikes I have completed, and as per the Norton workshop manual, the gaps in the piston rings are seperated ready for the 'install'. I see in the handbook the gaps in the two compression rings are 180° apart, top one facing the front, middle one facing the rear of the piston. The manual tells me to put the expander ring to the side of the piston, no problem with that. I can clearly see the gaps in the two scraper rings (rails) however I can't see the gap in the expander ring. I've looked really hard but no luck. What I have though is a dullish red 'painted' mark on the expander ring and I'm wondering if this is where the gap is. Furthermore, on the underside of both pistons there is red felt pen mark on the cast side of the inner 'boss' where the gudgeon pin locates through the small end. Using logic I'm wondering if the red mark visible on the expander ring matches up with the red mark on the underside of the pistons? Hopefully this is clear. Your thoughts.
Yes, it's that red mark - on…
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Yes, it's that red mark - on Hepolite Apex rings anyway, Actually two marks, one on each end of the expander. If you look very closely, with a magnifier if necessary, you should be able to see a slight difference between the gap at butted ends of the expander and the other gaps around the piston.