Just posting this while it is fresh in my mind, after swapping some chains and sprockets around this morning.
The CB/CL 175 up to and including K6 use a 428 chain. At some point, possibly late K6, definitely K7, this changed to a 520 chain, as also used by the CB/CL200. I', assuming that the later heavier chain was adopted for ( lack of ) maintenance reasons ?
Chains, with matching front and rear sprockets, are interchangeable between the two variants. CB175 has 16:38 sprockets, a 2.375 ratio, CB200 has 15:35 sprockets, giving a 2.33 ratio. CL variants are lower geared, at 16:40 and 14:35 respectively, giving both a 2.5 final ratio.
However, there are some proviso's. Front sprockets fit without issue, output shafts and mountings are the same on both engines. At the rear, the CB175 sprocket is thicker than the K7/Cb200 sprocket. This means that if a 175 sprocket is fitted to a 200 rear wheel, the 'pie dish' sprocket protector thing on the 200 wheel has to be discarded, otherwise the retaining circlip will not fit.
Vice versa, if a CB200 sprocket is fitted to a 175, the matching pie dish thing must also be fitted, otherwise there will be too much slack under the retaining circlip.
Aftermarket JT sprockets come with two sets of sprocket bolt mounting holes, in M8 and M10 sizes. OEM Honda sprockets just have M8 holes, which fit the original M8 cush drive / retaining bolts. However, there are some aftermarket retaining bolts on sale. These fit the cush drive rubbers correctly, but have M10 threads. The JT sprocket will fit fine with these, using the alternate set of M10 holes. If you have an OEM sprocket with 8mm holes, you have a problem, as I discovered today.
I did think about drilling the sprocket, fortunately abandoned that idea pretty quickly, and simply swapped sprockets and retaining bolts around. The 'pie dish' needed to have an M10 drill bit run through its M8 holes. This will not cause future problems if I revert to M8 bolts on this wheel, as the pie dish is centered correctly by the central hub, where the circlip fits.
Another slight gotcha. CB175 and CB200 rear wheels are interchangeable. The wheel spindle and all spacers are identical, as are the brake shoes and wheel bearings. However, the matching brake plates must be used, the 175 brake plate does not fit the 200 wheel correctly. Torque arms are the same length, but the CB200 brake plate has an M8 pivot bolt, as opposed to the M6 bolt found on the 175. So the 175 arm needs to be drilled out to take the M8 bolt, if used with a CB200 rear wheel. ( K7 uses same back wheel as earlier 175s, just has the 520 chain and sprockets )
1970 Honda CB175K4
1972 Honda CL175K7
1999 Honda CB600 Hornet
1970 - 1972 Random heap of CB/CL/SL 175 parts, slowly being reassembled ..