Bike not starting

[MJ310]

For A number of years my 1000sf has been a poor starter and I change the battery and it works again for a while. I switched to 240CCA types as they seem to work better. However after the last time it proved to be a problem I switched to LiFePO lithium and that worked really well for 5 months but then it started to fail to start again but when I tested the battery it was reading 1v so I had it replaced under warranty, unfortunately the replacement couldn't start it so I tried the battery out of my BMW which did start it (But only just and after a couple of attempts). Today I stripped out all the wiring in the started circuit and cleaned all the connectors, I found one of the connections to the solenoid were corroded so I thought I has it sussed. Put it all back together with another brand new 280CCA LiFePO and pressed the tit, nothing, bike would not start. Looks like it may be my starter but I had ruled that out as the bike always started on a new battery or with a jump start. Has anyone else experienced this problem with their MZ's? Has anyone stripped down their starter motor?

[MJ310]

I think it's down to the starter motor, its a Mitzuba SM-13. Does anyone know what other bikes use this starter? There are plenty of different variations on this starter but the casings are all different, obviously I need the correct match.