Attempts to lubricate the cable seemed to make it worse. Now the speedometer pegs out at the far right limit of travel when moving at any speed.
So today I did a proof of concept, using the Ram mount I had onhand for the Garmin Nuvi GPS (which had been serving as a speedometer anyways for long trips) and my iPhone with a free speedometer app.
The test was successful, it worked great. I'll postpone the taking apart of the wonky speedometer for now since the odometer and tripmeter appear to be working fine, it's just the needle that's OTL (Out To Lunch)
I've this more secure RAM mount coming from Amazon for the long term:
Update on Scarlett: Randy, the URAL dealer up at Fort Collins has started looking at it, but it appears he's going to have to remove the engine from the rig. That's all I have for now.