“For the want of a nail”

I thought of Benjamin Franklin’s thoughts on weak links as I was reassembling the S65 engine today. Ol’ Benjie put it much more eloquently than I ever could when he said:

“For the want of a nail the shoe was lost,
For the want of a shoe the horse was lost,
For the want of a horse the rider was lost,
For the want of a rider the battle was lost,
For the want of a battle the kingdom was lost,
And all for the want of a horseshoe-nail.”

When I reassembled the cases I took another closer look at the timing chain sprocket. It was worn but on an earlier inspection I thought I could get by with it, but now, considering how much time and $$ has already gone into this old engine, do I take a chance on the timing chain slipping a tooth or two with some potentially disastrous consequences? Or do I bite the bullet and replace the sprocket and chain while everything is mostly still apart? It might run fine for a few thousand more miles the way it is but it will always be a weak link – and worst of all, a weak link I’d be constantly aware of.

And there’s another factor to consider. Once the cases were bolted together I discovered that the crankshaft end play was way over the limit (20 thou vs. 4 thou), so pulling the cases apart again would let me shim that up as well and reduce the side-to-side sloppiness in the crank which, for an engine that runs 8,000 – 10,000 rpm, can be a problem.

So I did bite the bullet and ordered a new sprocket and chain which have now arrived. The next task will be to get the old sprocket off the crank (it’s a press fit) and the new one installed without destroying anything important.

And for shim stock? I have this old Harley Davidson beer can that should do the job just perfectly. I’ll have to make sure that enough of the HD branding stays visible to get a WTF????? out of the next owner when he realizes a 50 year old Honda has some Harley in it.