Topic: K8 Chain/Sprocket Replacement Questions

[Rosinante]

I am glad this thread exists, including links, because it forms an excellent discussion about the sprocket oddities on K8 bikes and likely also K7.  Honda moved the sprockets out just a bit, likely to make room for the extra width of these elevator chains (630) they put on these bikes.  These parts are not easy to find and a 530 chain makes sense because of greater availability and selection. The solution is provided in excellent detail by denward17 in Reply #16. 

I am asking for confirmation that my geometry is correct here.  The first two pictures show the inboard surfaces of the outgoing stock sprockets.  These are the surfaces installed against whatever they are fastened to.  In the case of the front sprocket it is the transmission final drive shaft, and the rear sprocket we have the wheel hub.  The front sprocket has a shoulder, moving it slightly leftward.  I believe the rear hub is wider on these bikes, so that the rear sprocket is also moved slightly outward.

The next two pictures show the surface of the new sprockets that I believe are also the inboard surfaces.  This surface of the front sprocket, with the shoulder goes inboard and this flat surface of the rear sprocket goes against the hub.  Right?

Also, there is a picture of the four nuts that attach the rear sprocket and two tins which were 'staked' against the hex nuts.  My plan is to restake and reuse these.  Honda probably recommends they be replaced.  I think I can get away with reusing these, as long as the nuts are properly torqued and the tins are nicely staked against the nuts.  Anybody think I am making a huge mistake in not replacing these?

And finally, there is a picture of the teeth of the front sprocket.  This is what a worn sprocket looks like.  The round parts are no longer round and the teeth parts are not even on both sides.

[Rosinante]

Oops.  Here are the other pics:

[Rosinante]

The 530 chain is smaller in every way than the 630.  Width of the outer edge of the outer plates is 21.5mm and 22.5mm respectively.  Only 1mm difference but there is a difference.  Same difference in the widths of the inner plates and also the diameter of the rollers.  The distance between the inner surfaces of the inner plates (width of the rollers, basically) of the 630 is around 9.53mm.  Oddly, this measurement on the 530 chain is closer to 9.7.

[rotortiller]

Rosinante, The 630 chain is over kill on a 50hp bike but it works. Chains in 630 of various brands can be had from Fortnine in a longer length cut to what you need. Sprockets can be had from vintage shops and Fortnine, try JT brand.  This should get you started. https://fortnine.ca/en/catalogsearch/result/?q=630%20chain&manufacturer=RK~EK~DID

[denward17]

Just to update thread, I have been using the following with a 530 chain:

JTF338.17
JTR284.48

I decided I wanted to lower the RPMs a little while cruising, so just ordered a 18 tooth front sprocket.
JTF288.18

Will let you know how it works out.

[Rosinante]

I got the JTF 338.16 and JTR 284.43 sprockets, for the same purpose.  Just a tad taller gearing compared to stock.  I like it so far.

I was not confident how much larger the front sprocket could be and still physically fit, but probably any front sprocket diameter would fit as long as it fits earlier bikes.