01-06-2022, 07:29 PM
An A7 would be quite an old plug, Dave. It was superseded by the AB7 some years ago so they might, simply, be past their best. The only difference is the size of the hex. It's Champion equivalent would be a D9 and they might be a bit 'hot' for a standard 7 engine. A6/AB6 or D16 probably more appropriate. However, today I've started to get my SWB Saloon ready to take to Morton. It's not been used properly since October 2020 when it wasn't running too well. Apart from keeping the battery charged up, I've not done much with it since then. It fired up pretty much first go even though it's got 19 month old petrol in it but it was still a bit 'rough'. Squirted a bit of light oil into the plug wells and looking at it ticking over I saw some bubbling and realised the Champion D16 plugs weren't sealing too well. Tightening them all made no difference but a change to a new set of AB6s transformed the thing. No bubbling so full compression. Maybe your friend's Ruby simply needs a new set of plugs.
Steve
Steve