There is much confusion over exactly what size, type etc. chain has been used on the primary sprockets of older British and American motorcycles. There are several “standards” for roller chain, including ANSI, ISO, BS, etc. Don't trust a quick visual inspection, or comparison of only a few points of reference when buying a chain or sprockets. Some types that appear very similar are not compatible, typically due to differences in the roller diameter. Others will work acceptably with only slight additional wear.
    Chain dimensions are usually given in the following order: 1st = pitch, 2nd = roller width, 3rd = roller diameter. This is not all the useful data, and cannot be used reliably to determine whether chain repair parts (master link, connecting link, offset link, roller, repair link, etc.) can be interchanged.

ASA Type	Alternate No	Pitch	Roller Width	Roller Diam.	Rows	Use
35		3/8” .375”	3/16” .1875”	.200”	1	H-D Hummer 125, 165, Super 10 primary
35-2					2	H-D 45 primary
35-3					3	H-D K/KH, Sportster; Indian Scout primaries
35-4					4	Indian Chief 74 & 80 primary
ISO 06B-2	Renolds 114038		7/32” .225”	1/4” .250”	2	BSA 1947-58 A7 & A10 early rigid & plunger frame; Triumph; Royal Enfield primaries
ISO 06B-3	Renolds 116038				3	Norton P11, Ranger, Commando; BSA A75; Triumph T150, X75 primaries
??	Renolds 114513	7/16” .4375”	?	?	2	Triumph T160
41		1/2” .500”	1/4”	.306”	1	Commercial size, not used on motorcycles
ISO 08B-1	Renolds 110046		.305”	.335”	1	BSA Gold Star, 1954-62 swing-arm pre-unit; Matchless; Norton Atlas; Triumph pre-unit primaries. Note: very similar to #428
40			5/16”	.3125”	1	Commercial size, not used on motorcycles
428	126			.335”	1	Note: very similar to ISO 08B-1
428-2					2	H-D Big Twin primary 1930-*
520	170, 135, Renolds 110054	5/8”	1/4”	.400”	1	BSA M20, M21; other singles rear
525	Renolds 110055		5/16”			Moto-X rear
530	50, 171, Renolds 110056, ISO 10B		3/8”			Common H-D, other big bike rear
630	60	3/4”	3/8”			Kawasaki Z1 rear

    British transmissions do not use the same primary chain type as the Harley-Davidson 45 or Sportster. Although they may appear similar, they will not work.
    There is one useful similarity: the single-row British primary chain types are frequently ISO 08B-1 (½” pitch, .305” width, .335” roller diameter), including some 1954-62 BSA twin swing-arm models. This is almost the same as ASA #428, used on Harley-Davidson big twin (not 45) primary chains since 1930.
    In my opinion, since they are not an exact match (the #428 roller is .0075” wider than the British 08B-1 dimension), a H-D big twin sprocket (#428-2 dual-row) will fit the British chain a bit too tightly. It may be possible to remove the extra material from both sides of the sprocket tooth row and use the British chain, but this may effect hardness, and I have not tried this method. However, the #428 chain will fit the H-D big twin sprocket exactly, and will be only slightly loose (.0075” extra side-play between the sprocket tooth and the chain's side-plates) on the British clutch drum, which will cause slight additional wear but nothing serious.     Almost all British transmissions use the same rear drive chain as the H-D twins, so no adapting or fabricating is required here. A common exception* the BSA M20 & M21 WD (military), and some other later singles which use #520; a sprocket from a similar BSA box in #530 may fit.