Britbike forum Forums British Motorcycle specific Brands Norton bulletin board Commando MkIII neutral switch oil leak

Hello,
After 41 years the transmission neutral switch started to leak oil. I installed a new Genuine Norton replacement switch and shortly thereafter it started to leak. Anyone have an answer or similar experience?

Thank you.

Brian

1975 Commando
1966 Bonneville

Brian,

Seems strange that a new switch would be defective in this day and age, so have you considered:
- is the box possibly overfilled?
- is the gearbox breather plugged?

.. Gregg

Defective new parts are becoming a way of life.

Is it gold colored, have a what looks like red fingernail polish at the edge that retains the black plastic end that seals the body and supports the two spade terminals which have wires already attached to them? If so we have sold a fair number of them without any problems. No not to insult you, but oil leaks can be tricky to source. Often the oil is not coming from where you see it at first glance. Also it would not be hard to pressurize the switch and check it. But of you believe it is leaking just return it to the person who supplied it.
John

Thank you all. The gear box oil level is right where it should be. Only vent I am aware of is from where the clutch cable enters the gear box. It doesn't appear that that is sealed in any way. I can feel it move when engaged any wiggle it when not, so I am sure it is letting air in and out as needed. Yes, John, it is the item you describe. I cleaned the entire area before installing the switch. Everything is clean and bone dry except for drips comng from the hex head of the switch right next to the red nail polish like area. I guess I'll assume the switch is bad.

thanks again.

brian

As it's a MkIII, there should also be a small brass vent (item [6] in link, below) in the inner cover immediately inboard of the clutch cable entry, however, contrary to popular belief, it would seem practically impossible for pressure to build up in the gearbox due to the 'open' clutch cable entry, sleeve gear, etc..

https://andover-norton.co.uk/en/shop-drawing/128/gearbox-inner-cover

Thank you. Never knew what that was. I just ran an inch long dental pick follwed by a three inch wire down the vent hole. If it was plugged, it was very subtle. I'll plan on ordering a new switch.

If you want to confirm with whether or not the switch is the source of the leak, perhaps you could try replacing the switch with a very short 3/8UNF bolt.

BTW, you do have the original sealing hadware installed, don't you ? (ie, Dowty sealing washer and close-fitting flat washer)

..Gregg

Very detail oriented tests have proven to me and many others who have observed the testing that the AMC/norton gearbox does not/can not hold any pressure without making a special sealing cable entrance. The brass vent on a MKIII or the hole in the round disc are entirely unnecessary.

99.95% sure it is the switch and not the seal sgainst the gearbox case. A new switch will be installed tomorrow.

Again thank you gor all comments.

b

Hi,
The final words - bad switch. Once removed, when you pressed in switch actuator buttom bubbles came out of the terminals. I installed a similar switch and it looks like the red nail polish like "sealant" is covering a larger portion of the terminal end. A suggestion if anyone is faced with a similar repair. Buy the original type switch, and not the new version that has spade connectors. The latter is about a quarter inch longer and really doesn't want to fit in the small space between the gearbox and engine.

b