Hi
I believe that sometime in 1960 the A10 carb was changed from an Amal 376 monoblock to a 389 monoblock. The bore of the 376 was
1 and a 16th inch and the 389 was 1 and 1/8th of an inch.
My question is was the cylinder head bore changed to accommodate the bigger carb bore ie; a different cylinder head?
If so, does anybody know when in 1960 this change took place?
Hi Keating,
I think that the 389 was for the aluminium head only which had a slightly bigger bore on the slightly down draught manifold.
Probably only Super Rocket and Rocket Gold Star?
Dave.
According to the Amal Catalogue the A10 Golden Flash had a 389/45 carb for 1960/61 with 1 and1/8 bore. The cylinder head part number for 1954 to 1959 was 67-1065 but from 1960 it was 42-0180 so there must have been a change to it.
The Golden Flash head got a 1 1/8 monobloc and head ported to suit it for the 1960 season models, the bikes fitted with frames prefixed GA7. It was one of a number of changes for the 1960 season bikes which firat appeared in August 1959.
Photo is from the 1960 catalogue with comment about increased carb size.
Thank's for the responses, the reason why I asked is that my A10 is according to the engine and frame numbers is a 1960 model but the cylinder head has a 1 and a 1/16 inch inlet bore when it should be 1 and an 1/8 for 1960. It had a worn concentric carb so being a 1960 bike I fitted a new 389 1 and 1/8 bore assuming the head was also 1 and 1/8 but it seemed reluctant to start at times. When I checked the head the inlet bore was 1/16 so I fitted a 376 I had left over from an Ariel Huntmaster and she seems to start easier, although I can't see why this should be as I think it should not not make any difference. I would appreciate any comments as to why starting with the matched carb and head bore should be easier or am I just imagining it! It's possible that the factory fitted a 1959 left over head from that year or a previous owner changed it for some reason.