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Throttle return spring?

PostPosted: Sat Jan 09, 2016 7:00 pm
by 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

Re: Throttle return spring?

PostPosted: Sat Jan 09, 2016 7:21 pm
by 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...

Re: Throttle return spring?

PostPosted: Sat Jan 09, 2016 7:26 pm
by 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.

Re: Throttle return spring?

PostPosted: Sat Jan 09, 2016 7:50 pm
by 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

Re: Throttle return spring?

PostPosted: Sat Jan 09, 2016 9:53 pm
by 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?

Re: Throttle return spring?

PostPosted: Sat Jan 09, 2016 10:14 pm
by Marty ULC
Warkton Tornado No.1 wrote:...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.

Re: Throttle return spring?

PostPosted: Sat Jan 09, 2016 11:41 pm
by Knowledge
Like, Marty

Re: Throttle return spring?

PostPosted: Sun Jan 10, 2016 10:10 am
by 507VBH
I guess it comes down to what the UK MoT requirements are!

Re: Throttle return spring?

PostPosted: Sun Jan 10, 2016 11:18 am
by HxPaul
Warkton Tornado No.1 wrote: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.

Re: Throttle return spring?

PostPosted: Sun Jan 10, 2016 5:25 pm
by 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.

Re: Throttle return spring?

PostPosted: Sun Jan 10, 2016 5:36 pm
by Storkfoot
507VBH wrote: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.

Re: Throttle return spring?

PostPosted: Sun Jan 10, 2016 6:01 pm
by 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.

Re: Throttle return spring?

PostPosted: Sun Jan 10, 2016 6:08 pm
by 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 :o :D

Re: Throttle return spring?

PostPosted: Tue Jan 12, 2016 12:24 pm
by grandpa
Storkfoot wrote: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 :o :D

It is why I have indicators.
Grandpa