Fitting starter motor

[chasbmw]

Fitting exchange starter motor to my 1150, bit of a wrestle at times but fitted well with dowel located properly( I think) no issue with mounting bolts anyway.
The issue is that the starter works, engages, then immediately drops out. Result is a non starting bike. Is this most likely to be an issue with whoever rebuilt the starter or operator issue? If the latter what needs to be done to rectify the issue.
Cheers charles

 

[JJH]

Did u check the ring gear? JJH

 

[chasbmw]

Doesn’t seem to be any serious wear, the bike is very low mileage only 17k, I’ve just checked the battery voltage under load, it drops to 10v then 9v.

 

[NeilDD]

Battery sounds like it's on the way out

 

[Pekkavee]

Is the + wire properly connected to the starter?

 

[NeilDD]

Chas,
Do you know how to use a multimeter?
If so set DMM to Volts DC mV range
Put 1 lead on battery +Ve
Put other lead on Starter +Ve
Do 2 measurements
First with every thing on but not pressing starter button
2nd when pressing starter button.

Anything over around 25mV means cable is no good.

I still think it's the battery