"Update: Got the water pump and speed sensor housing removed. Looks like the water pump shaft seal has been leaking-the speed sensor cavity is very rusted. I have the speed sensor plate screws soaking in break free at this time. When the speed sense/water pump inner plate was removed the drive to the camshaft end did not seperate and the roll pin connection, it was so rusted the the drive on the end of the cam shaft came off with removal. This drive assembly is not indexed to the camshaft end. The drive can go on in any of 360 deg., it will still sense speed but it can rotate on the end of the camahaft. Any ideas?"
The camshaft did not break, did it? As long as the camshaft is intact, and only the sensor rotor lobe pin rusted away, then you are OK.
The lobe is held in place by a solid pin and only aligns in the correct position. The pin goes into the cam first and the lobe then slips over the pin into the notched area on the lobe. If the pin is missing or rusted away, just get another pin at the local hardware store. You may have to trim or modify it, but I have done that myself because of a rusted out pin. No problem there. While you are in there, replace the water pump mechanical seal. You can buy one from Honda, pt# 19127-657-023, about $46. Or you can use the Yamaha seal (as I have done several times), Yamaha pt# 11H-12438-10-00, about $18 as of two years ago. It fits perfectly, and may be easier to get.
BTW, can you do me a favor? While you have it disassembled, can you measure the impeller collar for me? It is the slip on collar that goes behind the sensor rotor lobe. I need the outside diameter and the overall length, inches or mm's are OK. I know this is an odd request, but last year when I was replacing the seal, I lost the collar, and made one from a bronze bushing at the hardware store. I want to make sure it is within proper specs & size. Thanks!!!