Te310 11 Plate Uk Based Electric Starter Issue

The bike starts ok on second kick. Thing is I want it to work as my son wants to learn to ride and therefore would be easier.
The starter trusts to spin but the solenoid just clicks . When I remove the unit from the bike it spins fine : I have cleaned the the starter too and fitted new battery

Any suggestions. I will take plug out tomorrow see if it turns the motor. Arbhhhh

I'd guess one or more of three issues:

• low battery capacity, or questionable battery leads for example
• too much valve clearance ('specially the left intake which activates the automatic decompressor ADC)
• scored, gouged, or worn ring/worm gear interface (might be hard to see) causing high starter drivetrain drag

good luck.