Starter gremlins

I have a 1978 Moto Guzzi 1000SP. I have had it for many years and it has given me no problem with starting, until recently, but I cannot find any fault.

Off the bike the starter and starter solenoid work correctly. On the bike they refuse, even though the relay works and cables are intact. I press the starter button, the relay clicks but nothing else happens. If I disconnect the cable from the relay to the solenoid and attach a bulb it lights up perfectly.

The Motobatt battery is not the issue. It is not new but holds a good charge and has sufficient oomph to work the starter on the bench. I have even tested it all with an identical battery from my Le Mans 2, but no change. I am no electrical wizard. I understand the basics I think but this has mystified me... hence this cry for help.

Phil Dimond

Hutch says: Three things spring immediately to mind, both will affect operation when there is load on the starter but not when it is not trying to turn the engine, i.e. no torque required.

Is the starter motor well earthed? Try with a jump lead from the body of the starter to the earth on the battery.

Replace the heavy lead to the starter as they can rot internally and build high resistance – again try with a jump lead to test.

The internal insulation on the starter windings are breaking down under load – you’ll never measure this statically just replace or have the motor re-wound