Right here's a strange one. The crank on my ST1100 has a keyway cut into it. It looks like they were planning on using a Woodruff type key (in as much as one end is curved). Trouble is it's neither 4mm nor 3/16"....

So is there some esoteric Japanese thickness Honda used? I can't imagine they used a random figure. It looks like 4.5mm keyway cutters are available but not 4.5mm keys? Eh?????????

This is my spare crank for pondering purposes....



Help pleeeeeeeeeease!

Any if you're wondering why I didn't just use the keyway on the standard crank pulley- this is why (don't think it'll take supplying a blower with 20Bhp)....

It looks more like a 'register' rather than a keyway. Cut to fit a tang in a pulley......much like the bottom piccy!

Yes I'm moving towards that conclusion.... Would be a right royal PITA though- just asking for a nice pulley on there.... Still fancy nicking 20bhp or so off it but it's going to get even more complicated if I'm asking whoever does the machining of the pulley extension to start fabbing up weird sizes. Would have been much nicer if I could have just banged a standard key in there. Grrrrr....

Can you not just buy a sprocket and do a little bit of filing?

Is it interference fit that requires cam, crank, and pulley locks?

It's not an interference fit- in fact it looks like they were thinking of possibly using a splined shaft because the inside of the pulley has splines cut into it. I'm slowly coming to terms with the fact that it'll need to be a custom key...