SF1 stuck in neutral/first.

C

ColinJ

New member
Location
Aberdeen
Hi Folks, I am recommissioning an SF1 which I bought as a young man in Italy in 1991. I drove the bike back to London with no problems apart from the electrics. I've done a cosmetic restoration. The engine has not been taken apart. So I took it out on the road the other day for the first time and it would only select first gear. I took the gear selector casing off and everything seemed in order. I read various posts on this forum and it was suggested that the neutral light switch may be the problem. I removed it and the gears now appear to select OK. So my question are

1) Why should this suddenly happen, the switch has not been disturbed?
2) What can I do to prevent it happening again?

Thanks Colin
 
Possibly gunk build-up within the switch, preventing the plunger to move freely. This will not allow the selector drum to move past the neutral position going up from 1st. gear.

Either clean out the switch, lay it in solvent for a couple of days and work the plunger until it moves easily, or fit a new one. These need to be shimmed correctly to ensure both smooth shifting and reliable neutral light switching.

piet
 
The switches are available from Motalia in the Uk, he bought out the entire stocksfrom the manufacturer, of around 4,000, but he will tell you that the one you need is the la.........................................snore
CLEM
 
I think that the neutral switches are rather hens teeth. If that's your problem, you can always dispense with it and just plug the hole. Would be an interesting test to be sure your problem is there.
Otherwise, selector half drum spring?

Paul
 
sfcpiet said:
Possibly gunk build-up within the switch, preventing the plunger to move freely. This will not allow the selector drum to move past the neutral position going up from 1st. gear.

Either clean out the switch, lay it in solvent for a couple of days and work the plunger until it moves easily, or fit a new one. These need to be shimmed correctly to ensure both smooth shifting and reliable neutral light switching.

piet
Click to expand...
Thanks, Ill try that, I just bought a couple of shims as well.
 
CLEMTOG said:
The switches are available from Motalia in the Uk, he bought out the entire stocksfrom the manufacturer, of around 4,000, but he will tell you that the one you need is the la.........................................snore
CLEM
Click to expand...
Thanks Clem, I called Motalia, he does have any. I'll clean it up and fiddle with shims.
 
Thanks for all your replies. I have bought some shim washers, I will clean up the switch, fiddle with the shims. If that doesn't work I'll fit a plug.
 
If Laverda switches aren't available, perhaps there's something else that'll fit. For example, I recently replaced a switch in my car's gearbox (diff lock light switch - photo below) and it looked just like a neutral switch from a bike. It's been too many years since I pulled a Laverda switch out and I can't remember the specs (thread and detent ball depth), but the picture in the parts book looks like any other detent switch. Laverda would most likely have sourced them from Bosch and I doubt they'd have been a special order. So something from another bike or car might fit.

What's the thread size and depth (sealing face to tip of plunger) for the Laverda switch? You never know your luck, this one might be a close match.
 

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Dellortoman said:
If Laverda switches aren't available, perhaps there's something else that'll fit. For example, I recently replaced a switch in my car's gearbox (diff lock light switch - photo below) and it looked just like a neutral switch from a bike. It's been too many years since I pulled a Laverda switch out and I can't remember the specs (thread and detent ball depth), but the picture in the parts book looks like any other detent switch. Laverda would most likely have sourced them from Bosch and I doubt they'd have been a special order. So something from another bike or car might fit. What's the thread size and depth (sealing face to tip of plunger) for the Laverda switch? You never know your luck, this one might be a close match.
Click to expand...
That is an good suggestion, although I've ridden an old Triumph for years without a neutral light. i'll just be happy if the gears select OK. I cleaned up the neutral switch and reinstalled it. The gears appear to shift. I'll take it on the road today and see if it is OK.
 
correct Cam, BMW ones fit but are two wire type, this interupts the positive, wheras the Laverda one is an earth switch with a single wire, not unusable of course, but re-wiring would be tiresome, mine has worked for years and just plugs the hole.

the switches did seem to be a queer type, but then again I may have been influneced by mr. last on on the planet.
CLEM
 
Two wire switch would work OK. Just earth one of the wires. The switch doesn't care if it's interrupting the positive or negative side of the light.
That's assuming the switch is normally closed (contacts open when the plunger is depressed). Even even in the unlikely event that it's normally open, it can be made to work via a relay.

If other options don't pan out, try fixing the old switch. Chuck it in an ultrasonic cleaner or something.

Last resort: the switch doesn't work anyway, so you have nothing to lose if you bugger it up completely. Dig the guts out of it and try to re-build it. It's not some mysterious magical device. It's just a switch.

I like having a neutral light. It's not essential, but it's a nice thing to have.
 
Dellortoman said:
What's the thread size and depth (sealing face to tip of plunger) for the Laverda switch? You never know your luck, this one might be a close match.
Click to expand...
M14 x 1.5
18 mm threaded section length
face to tip 22 mm though this one is still stuck and worn

VERY similar (read "identical" though others deny this) to those used in the Zane' bikes so a suitable substitute would make both communities happy.

Did you by chance measure your Mitsu part before installation?

Breganze neutral switch - ps.jpg
 
Blimey, that looks almost identical to my Mitsubishi diff lock switch. The old one I pulled out might still in the workshop rubbish bin. I'll see if I can dig it out and measure it.


Edit ... some hours later:

I found it. Had a bit of a clean-up in the shed while I was at it.

It's the same thread M14 x 1.5, but this one is a wee bit shorter. It's 18mm from shoulder to tip, so it's not long enough for a Laverda neutral switch. If it had been longer it could probably be used by stacking shim washers under the head.

Maybe someone who works on car transmissions can come up with a longer one. Perhaps a reversing light switch. They've gotta be out there somewhere.
 

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