Throttle return spring?

[507VBH]

Hi,

I have not messed around with Lambretta engines since 1978 and I cannot remember whether the throttle has a return spring. Is the throttle supposed to snap shut when the throttle grip is released? Modern bikes do but I recall some old stuff doesn't.

Cheers

[lammydave]

the only return spring is inside the carb... except on some Spanish models which had one on the control rod in the headset
there are mixed opinions as the whether they should snap shut or not...

[Warkton Tornado No.1]

Ha!

All throttle controlled machinery should 'fail safe' by snapping shut. I used to think my first Lambretta had cruise control.....

It can be done achieved by careful routing of the cable to ensure no clamping, plenty of lube if necessary (some prefer dry) a stronger spring in the carb &, if all else fails, adopt the Serveta 'cheat' & install a torsion spring on the throttle arm. That's what I do. Especially when gear change pullies are adapted to give Q/A throttles.

[Storkfoot]

If you have indicators, like late model Servetas, that's fine. If you are on the race track as a safety device, yes.

If you have to signal right using your hand, no. That's why they are designed to have a degree of interference

Discuss LOL

[Warkton Tornado No.1]

Storkfoot is correct in saying that there is some use to a sticking throttle whilst turning right.

However, when on track or road, if you 'lose it', as I have many times, it’s a much better option to have a self closing throttle.

Here's another curved ball, though. How come those four strokes, as we all know, give phenomenal engine braking, yet MotoGP stars manage to roll off the throttle on the wind-down lap & just keep rolling whilst standing on the pegs?

[Marty ULC]

...How come those four strokes, as we all know, give phenomenal engine braking, yet MotoGP stars manage to roll off the throttle on the wind-down lap & just keep rolling whilst standing on the pegs?

Because they are gods.

[Knowledge]

Like, Marty

[507VBH]

I guess it comes down to what the UK MoT requirements are!

[HxPaul]

Storkfoot is correct in saying that there is some use to a sticking throttle whilst turning right.

However, when on track or road, if you 'lose it', as I have many times, it’s a much better option to have a self closing throttle.

Here's another curved ball, though. How come those four strokes, as we all know, give phenomenal engine braking, yet MotoGP stars manage to roll off the throttle on the wind-down lap & just keep rolling whilst standing on the pegs?

Theres a lot of difference between a throttle that you have to twist to shut off and a "sticking" throttle.And I would like to know why,if you lose it, its much better to have a self closing throttle.

[Warkton Tornado No.1]

I would like to know why,if you lose it, its much better to have a self closing throttle.

If you lose it, inevitably on a bend, if the power remains on, rather than shutting off, you have very little chance of retaining control. Just trying to regain control, particuarly on a right hander with the tendency to open the throttle even more is something I would imagine most of us seasoned riders have endured, especially on a greasy roundabout.

Then there is the safety of others to consider. A bike careering down the road or track, having righted itself as they often do, is a liability that I would not wish to be responsible for, having witnessed it.

[Storkfoot]

I guess it comes down to what the UK MoT requirements are!

You shouldn't fail an MOT for this. The interference nature of the throttle is specifically referred to in old Lambretta manuals.

[Warkton Tornado No.1]

I doubt that all MOT testers would assess the self closing of the throttle & it is not specifically referred to in the MOT manual issued by HM Government.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/447285/mot-inspection-manual-classes-1-2.pdf

The document majors on more important things like number plate size & exhausts….

I think we should all conclude that this all comes down to personal preference.

[Storkfoot]

I do agree. I have seen both sides, an off with a racing throttle, but also a route home from work where I have to signal right to get into the right hand lane of a busy and fast dual carriageway. That can be scary with a closing throttle. Trust me

[grandpa]

I do agree. I have seen both sides, an off with a racing throttle, but also a route home from work where I have to signal right to get into the right hand lane of a busy and fast dual carriageway. That can be scary with a closing throttle. Trust me

It is why I have indicators.
Grandpa