So compact and so innovative was the first-gen chain-driven cam V4 engines that the engineers had to put the cam chain tensioners within the chains instead of outside them. Inside-out, you might say. And automatically tensioning. And it worked and worked well. For a while. But the Hy-Vo type cam chain wears pretty quickly. The tensioner therefore had work to do almost from the get-go.

The cam chain is massive, dense. Just a little bit loose and it clatters like nobody's business. Really noisy. Many riders choose to put up with it, but what kind of enjoyment is that?

The tensioner is pulled into constant tension as the chain wears by the spring. To keep the chain from overcoming the spring, a self-locking plate clamps the small diameter rod, exactly the way those old screen door pumps could be locked open. Remember those? If you remove one of these tensioners you will notice a spot where the rod is polished. This is because the clamping is under-designed, it is inadequate. Honda replaced a lot of these under warranty-- my toolbox still contains many of the as-shipped safety pins that kept the new tensioners retracted until after installation. I collected them. Honda later revised the tensioner design in two ways. First, they changed the angle at which the rod approaches the lockplate. And they enlarged the diameter of the rod. This definitely helps, as I have observed that the revised part lasts longer. Unfortunately, neither the original or the revised part is available anywhere in the world. The last pair (the bike has two of these) I bought used and fortunately got revised units, though slightly used. For a project before that one I was able to find new ones in Italy. But that was five years ago.

There are some folks modifying these now in attempts to keep these bikes running. They have come up with ways to make the rod and plate lock despite the worn spot, in some cases going so far as to drill out and reposition the rod angles even more than the revised parts were. More power to them.