Hi everyone. I?m new to the forum having only found it recently. Lots of great information and insights on the A10 that I could have used a few years ago.
I?m in NV, USA and have several BSAs including a 1961 A10 that is posing as an RGS- but doesn?t quite make it! I bought it 9 years ago from an owner who had it ?professionally? built by a local restorer, who did some strange things to it, like using 10.5:1 pistons (more on that later), piston rings with 52, 42 and 28 thou end gaps,- the bike would smoke like a WW2 battleship trying to hide, which is why the PO sold it, a magneto that would not fire when hot, worn out gearbox bearings and other travesties.
My Question: After the timing side bush failed last fall, I took it all apart for a replacement and discovered that the Hepolite pistons were 10.5:1. Since I got this bike, I have ran it either on 50/50 91 octane pump gas and 100LL aviation gas, or a mix of pump and 110 racing gas. Any less than that and it knocks like crazy under load. Has anyone had good experiences with 10.5:1 pistons? Is there a change to any other engine part that should be done to work with them? Should the timing be reset from the 11/32 before TDC? Should I buy lower comp pistons? I rather not spend the $s but if these are not a good idea I?d change them the next time its apart.
Thanks in advance for your comments. Sam.