My starter relay is a "Hitachi - 12v - MS5A- 181 or M55A". This must be an after market replacement, right? If it is, is this the preferred model or is there a better relay?
Thanks.

907 use Hitachi relay, but i cant remember now number.... Same as in newer modells.

It isn't a replacement.
On both 907s I have Hitachi relays and they work very well, unless the connections were rusted.
Check for rusty connections.
Ciao

Amazing what the cleaning of all connecting terminals/cables for starting the bike and a new battery will do for instant firing of the bike! Before had a delay of about 1-2 seconds and weak starting sound when fired. Now, starts just like a car!

But LUCKILY it is NOT "a car" Its very important to keep all connections and cables in good condition and well lubricated against rust with right lubricants. That can solve alot of all elerctrical gremlings in Ducati.. especially in charge system!...

Suggest you make a small hole in the bottom of the rubber boot over the starter motor "+ve" cable.
This lets the water out before it rusts the nut to the bolt.
Mine was fully rusted and a major pain to fix.
Auto electrician also said to paint over the whole nut/bolt to keep out the water as its the main reason for failure

according to ca cycle works web site , the yamaha starter relay works, USD$42
http://www.ca-cycleworks.com/shop/catal ... /elec.html
go down the page to battery and charging

I did put the little drain hole in rubbe boot on stater cable. Was obvious what was happening when I pulled off the boot for the first time. Yep, rusty connection do to water. Electric grease works fine also. Wonder if the Yamaha starter relay is stronger than the stock Hitachi? It was a common switch to make on my Aprilia Falco to replace stock relay with the Yamaha one for better "umpphh". Not electrical type so don't know where to get specs to compare both of the relays.

Thanks for the help.