The speedometer and odometer are 2 distinctly different instrument parts. The speedometer needle "wandering" can be cured with a fresh application of silicone watch oil.

The odometer drive system is purely mechanical. It sounds like the odometer is OK, but at 5 miles the resistance to advancing the digits becomes too much and something starts to slip internally. There is no "clutch" function designed into the odometer, but there are press joints which are known to loosen over time and can slip thus causing the issue you describe.

This is not something you want to do yourself. Go ahead and pack it off to one of the service units listed in the Airmail. It will be a simple and inexpensive unit service. If you do it now, you'll probably miss the big wave that hits at the beginning of riding season and have it back in short order.

Thanks for the info. Wirespokes seems to be offline so I'll ship it to Austin, though he wasn't sure he had parts for it. Anybody know if this speedo is used on other bikes? I may be in the market for a used unit.

Rick at Overseas in Austin had the speedometer back to me in less than 2 weeks. A premliminary test ride and all was OK. More miles to come when this cursed cold weather warms up.
Rick was easy to deal with. The repairs were fairly complex and not inexpensive at 250.00, but it was worth it to keep the bike original.

$250 seems to be the minimum charge for this work. Believe me, you got a deal.

But, glad to hear you're back on the road again !

75 mile ride yesterday and speedo working as intended.
I thought the price was very fair and I can recommend Overseas to Airhead members.