SF2 – neutral switch open when engine hot

[mikeb]

Hi

When the engine is cold, neutral light works fine. But when its hot, the switch stays open and light stays off. Ive read about shimming it etc, and can only assume with heat there’s a slight expansion of the alloy cases and the switch no longer makes sufficient contact with the lobe on the selector drum. If so I’d remove shims, make it closer… have I got that logic right? Or, maybe the switch is fked? Do they do that?

Asking as its going to be tricky to test if the engine needs to be hot to know.

thanks

PS – and not reopening a can of worms - inconvenient when the PO wired the starter solenoid through the neutral switch. Lucky I discovered that at the top of a hill. I’ve now added a parallel switch on the clutch with diodes etc.

 

[piranha-bro2]

Very annoying that weirdo wiring - so would only start in neutral??? I don't even have a neutral light, let alone oddball wiring to clutch levers and neutral switches!! Never dropped a bike from trying to start in gear. You realise pretty quickly!

I think you're on the money with the expansion theory. Try removing a washer/shim. Tricky because the sump is full of oil! Best done during oil changes - and then rest the light while it's out - I guess you could try and measure the distance to the lump on the selector drum that pushes on the switch and do some calcs - or just suck it and see.

 

[Tippie]

There is an electrical contact in the switch, it is possible that over the decades it has deteriorated and when hot does not give good contact.

 

[Jota Rob]

Its quite possible/ probable that the switch contacts are burned if it was the earth return for triggering the starter solenoid ( without using a relay).
Since its only designed to illuminate a warning light 4w.

 

[Cccg]

From past experience on many other Laverda motorcycles it's either incorrect shimming, easy just add another 0.5mm or thinner shim, or the the switch is on it's way out going to open circuit. Or wiring shorting out once hot.