Things Eh! - Findings from a Canadian A Twin

Robert Watson

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VOC Member
Having acquired a basket case A Twin just over two years ago, and having started (and in some cases finished) all manner of bits on the rebuild - wheels, gearboxes, front forks etc. today was the day we split the cases. Having been told that there was likely one postwar and one prewar conrod in here we were most interested to see what was what. First we found a couple of stripped threads, bolts shoved in hard with montains of red gasket goo, but apart from that no big surprises. Everything appears to be in good shape with the cases. Next we pulled the crank and removed the pistons. Both rods appear to be of the same manufacture and sliding a wrist pin through both rod small ends, determined that within reason they were the same length. Next we hung the assembly on the rails to see how much weight it took to balance them - Lo and behold, with a not super accurate scale (+ or - a gram or three) the balace factor turned out to be 35-36%. Perhaps when PEI quoted the 36% factor he was thinking of the A and not the postwar crank at 46%?????? The next interesting revelation, despite being assured by Bob Stafford and others that the rods are of the same length pre and post war -- as we had noted on other A rods, they measured 7.283 c/c.(No doubt + or - a couple of thou) That number is .033 longer than a post war rod, or about 1/32 of an inch. One more reason (besides the shape of the cumbustion chamber) that you get higher compression with new pistons in an A.
Any one have any comment???