Hi all,
I have a 1957 Road Rocket. The engine and frame are original. Frame EA710010, engine CA10R4652, HHC (meaning high compression). I acquired an A10 engine, S/N "CA10RR4139", HHC. Note the 2 R's. Does anyone know the significance of "RR" in the S/N as opposed to "R"? Upon disassembling the engine, I found the crankshaft to be a one-piece casting i.e., crank and flywheel fully machined from one single piece of cast steel. It looks very different from a late A10 crank but weighs the same. It has the sludge trap as does a std crank. Anyone ever seen such a crank? See pic's.
Greg, Virginia, USA
I have seen a number of Road Rocket engines prefixed CA10RR on bikes exported to the USA.
Not sure about the crankshaft.
The early Road Rockets used a small bigend journal crank, with oil drilling sealed with small plugs either end and no removable sludgetrap tube. Flywheel attached with 6 bolts.
A bit later they were fitted with a large jounal crank with oil drilling sealed with small plugs either end and no removable sludgetrap tube.
Late production Road Rockets fitted with another different crank different shaped webs, (the type used until 1963) with flywheel attached with 3 radial bolt, large bore oil drilling and fitted with removable sludgetrap tube and large sealing plugs.
Hi,
I have seen one of these cranks and heard of a few others. The one I had a brief look at did not have the heavily machined flywheel area. I believe that un-machined it was a heavier crank than standard and one was used by the late Brian Birch in his well known combination.
He claimed it gave quite a bit more torque/flywheel affect once spinning.
Dave.
Thank you for the replies. I restored the Road Rocket I have and used the late crankshaft with the 3-bolt flywheel. I also installed the later 357 Super Rocket) camshaft. I'm considering rebuilding this "RR" engine to see if it behaves differently with this crankshaft. Although this crank weighs the same as the late 3-bolt crankshaft, the diameter of the flywheel is smaller than the 3-bolt crank. I assume its purpose is to rev up faster, but probably at the sacrifice of torque.
Greg
Hi Greg,
Have you confirmed that the stroke is A10 rather than A7? BSA did have the special A7s for Daytona.
Dave.
Thanks for the reply, Dave. Here is a picture of both cranks. The one on the right is a std. late A10 crank. The half stroke on both is 42 mm...half of the engine stroke of 84mm.
Dave,
I* looked up Brian Birch on Google and found little other than his obituary. Do you have any additional info about him and his BSA?
Greg
Hi Greg
I think what you have there is one of the first large journal cranks fitted to the last Road Rockets and early Spitfires before the introduction of the more common large journal crank with the flywheel secured by three bolts.
Sometimes referred to as the heavy or solid crank, these also have a separate flywheel but give the appearance that they are solid due to having no visible bolts. Yours looks like one of these rare early cranks with the flywheel removed.
Jim
Hi,
Brian Birch was pretty much one of the founding members of the BSAOC. He served on the National Committee for many years and as President and Vice President. He worked hard for the BSAOC and attended many Club events on his BSA outfit latterly fitted with a Watsonian Monaco sidecar. As well as the crank he preferred the 67-334 cam for better low to mid range and so better for an outfit.
I will see if I have a photo of his bike.
Dave.