LCGB Forums

Hi all,
I'm fitting a top end kit to my S3 Li1125. I intend to retain the original gear box but am pondering overall gearing. Keep the original 46/15 sprockets or change, and if so what to?
Any thoughts appreciated.
Thanks.

It depends on the kit you're fitting, exhaust and any tuning work that may have been done to the kit.

If you get any advice without supplying this information then you'd be better off ignoring it. It's too easy to get sucked into the idea that an increase in any area requires a reduced overall gear ratio.

Give us this extra information and you'll get good advice.

It just depends wether its late S3 or early S3,they both have the same top gear but everything else is different.

you might find it helpful to use the google search feature ...theres plenty of information and advice out there.

Cambridge Lambretta
MB Developnents
beedspeed
etc etc

http://www.mbdevelopments.co.uk/lambretta/lt7.html
http://beedspeed.com/html-pages/Lambret ... oChart.htm
http://www.lambretta.co.uk/downloads/gearbox.html

Thanks all.

Early S3, Mugello 198 top end and Clubman exhaust.

1-up, riding mostly short distances, rather than touring.

I believe you good go to 17 tooth front sprocket and get good results with a final gearing of 5.01:1 that will give you 61mph @ 6000rpm as opposed to 54mph @6000rpm. You will need a longer chain.

CHRIS in MARGATE wrote:I believe you good go to 17 tooth front sprocket and get good results with a final gearing of 5.01:1 that will give you 61mph @ 6000rpm as opposed to 45mph @6000rpm. You will need a longer chain.

I agree but I think you meant 61mph as opposed to 54mph.

81 link chain will work with that combination.

I'm all for helping anyone Skip , everyone knows that, but you don't seem to making any effort to learn a little by your own efforts by using the search button.
You just seem to want the answer handed to you on a plate .
I've supplied 3x links to some excellent articles and gearing selection advice which will give all the answers anyone could ever need but obviously you haven't bothered to read them and learn something about gearing for yourself .

Owning, repairing, restoring and maintaining our vintage scooters is a fantastic pleasure and rewarding experience and part of that, to my mind, is the journey of discovery. Learning little bits here and there that eventually builds into a personal library of knowledge and experience.

I'm not trying to be critical or knock you in any way Skip .if I were near you i'd be the first to come round and help you with your scoot resto and eat all your bacon sandwiches and christmas cake ....but really buddy you need to read through the 3x links I gave you and then if you still have any questions by all means come back and ask . We gain nothing of value in life by just having stuff handed to us on a plate .

He's reet ya knar.

I knew nowt about Lambrettas until I bumped into some mad blokes on a ferry who were coming back from Austria in 2013 (I think) on these old Lambrettas.

Since then I've filled my head with knowledge at about the same rate that I've emptied my bank account.

It's the learning that's interesting for me.

However, we're not all as interested in the same aspects. So if someone needs or wants to be spoon-fed is there any harm in that?

well I guess I just find it frustrating when it looks to me like peeps don't make any effort at all to do a basic search .

The first paragraph.......... on the first page ...........of the first link .........that i provided has the answer that Skip is seeking

I doubt that there are many folk that knows as much or has made such a contribution to lambrettas than Mark Broadhurst . His wealth of experience and extensive testing, tuning , building and design and manufacturing is awesome.

if the guy says that the best gearing option for a Li125 S3 is a standard Li150 gearbox then I for one ain't gonna argue with that.

Quote ;- Li 125 Late Series 3

This gearbox tends to over rev which would limit its top speed.
Increasing the front sprocket to a 16 tooth would raise the gearing to have an overall top ratio of 5.30:1 which possibly its best set up.
Swapping the gearbox to a LI 150 Italian would improve the all round performance.

GEARBOXES THAT WORK

There are hundreds of gearing combinations available for Lambretta engines.
What is best for each engine presuming the gearbox is original to the engine has already been covered.
MB Developments recommend for most engine applications the LI 150 Italian and SX 200 gear box.
The reason is; both have reasonably good gear ratios and jumps between each gear, which suits nearly all road going Lambrettas.
The gear parts are strong, they don't usually break or wear out.
You can fine-tune the gearbox by changing usually only one sprocket in either direction.
Slight differences in tyre sizes can also fine-tune the gearboxes further.
MB Developments

Johnny,
your links were helpful thank you, and yes I did use them and read the information they provide. However, from what I have read, previously and on the websites you suggested, it seems to me there is more to optimising gearing than numbers of teeth on cogs and sprockets. There's no right and wrong answer and I'm not expecting anything "on a plate", it's my decision to make after all. There is however a wealth of experience in the Lambretta community and numerous people willing to share their experience. If you're not one of those, so be it.

Please excuse my earlier typo.
54mph @ 6000rpm with current gearing set up.
Waiting on the 1st tee with cold fingers !

skip123 wrote:Johnny,
your links were helpful thank you, and yes I did use them and read the information they provide. However, from what I have read, previously and on the websites you suggested, it seems to me there is more to optimising gearing than numbers of teeth on cogs and sprockets. There's no right and wrong answer and I'm not expecting anything "on a plate", it's my decision to make after all. There is however a wealth of experience in the Lambretta community and numerous people willing to share their experience. If you're not one of those, so be it.

if you have actually read the links as claimed why are you ignoring Mark Broadhursts advice ?

Do you seriously think that any LCGB members are going to know better than MB ? maybe you think you know better .....is that it ?
If you don't know how to work out which gear set and ratio is best for your scooter how are you going to decide which advice is correct ?

There is a right answer ......read the gearing article on the link I provided it will tell you all you need to know.

Do you seriously think that any LCGB members are going to know better than MB ?

In defense of LCGB members I think your being a little bit disrespectful regarding the vast knowledge, expertise and experience that many members have.
Maybe the fella just wants to discuss possible options and learn first hand from people with similar set ups.

I think all the information anyone could need on Lambretta gearing selection is in the links I provided .

I appreciate what you are saying and I also enjoy shooting the breeze about any Lambretta subject but I do expect an enquirer asking for advice to at least do some basic searching and research before asking for advice so at least they have a basic understanding of the subject.

Sorry if your view is different but thats life . Its not right or wrong its just a personal view and opinion

There's a really good gearing calculator on scooterhelp.com which you can use to see what results you can expect. But it's also good to ask others what they experienced. My muggy 198 pulls an Li 150 gearbox with a 16 front sprocket and it's a really nice ride. 60 mph at about 6k rpm is just right (imo)

(The exhaust makes big difference too)

Maybe we should all stop reading this and go to the MB site...
I for one like the 125 box it has a low first gear to get you going and is favoured by those with sidecars or big wives, you can then mess about with the front cog and keep the rest as is with great results. I had a big conversation with a mate about binning mine and running a GP200 box and the gearbox calculator gave as near as dam it the same final drive. £300 better off than sticking with what I had.
You cant beat a bit of suck it and see. in my case I had a casa kit that pulled like a train but had no revs so it pulled a 19 front sprocket that I was told was way too tall. yes right.
The gearbox calculator is great but you need to know what revs you are likely to make and pipe and other things make a big difference, handy if someone says XX may be better, if what you have works out at the same figures. try to avoid any combo that needs a stretched chain, IMO better to go for the next one up. If you don't ask you will never know welcome skip123

I think that a vital piece of information in Skips initial post is being completely overlooked.

Skip has stated that he intends to keep the existing gearbox which is an early series 3 Li125 gear set

This gearbox has a very high first gear ratio which means that it will rev high very quickly requiring a quick gearchange up to second gear.
The other problem with this particular gearbox is there is a huge gap between first and second gear and again between second and third gear .This will result in the engine falling flat on its face with the first two gear changes . This power drop will be made a lot more pronounced with a bigger capacity engine like a 198cc.

Although a chaange to a 16T drive sprocket will improve the overall final drive ratio to 5.30 the big gaps betwween gears will be more noticable.

If you are looking for a sensible spread of gears that have the strength to take the exta power and give you a respectable final drive ratio of 5.22 (same as LiS150 series 3 special ) and good low down grunt then the only sensible option is to fit a Li150 gearbox and possibly add a 16T sprocket for an improved 4.9 final drive ratio and higher top speed.

Basically that is what Mark Broadhurst is saying in the first link I provided.
If anyone has a better option than that i'd be interested to hear it

johnnyXS wrote:I think that a vital piece of information in Skips initial post is being completely overlooked.

Skip has stated that he intends to keep the existing gearbox which is an early series 3 Li125 gear set

This gearbox has a very high first gear ratio which means that it will rev high very quickly requiring a quick gearchange up to second gear.
The other problem with this particular gearbox is there is a huge gap between first and second gear and again between second and third gear .This will result in the engine falling flat on its face with the first two gear changes . This power drop will be made a lot more pronounced with a bigger capacity engine like a 198cc.

Although a chaange to a 16T drive sprocket will improve the overall final drive ratio to 5.30 the big gaps betwween gears will be more noticable.

If you are looking for a sensible spread of gears that have the strength to take the exta power and give you a respectable final drive ratio of 5.22 (same as LiS150 series 3 special ) and good low down grunt then the only sensible option is to fit a Li150 gearbox and possibly add a 16T sprocket for an improved 4.9 final drive ratio and higher top speed.

Basically that is what Mark Broadhurst is saying in the first link I provided.
If anyone has a better option than that i'd be interested to hear it

I have used an early 125 gearbox with Mugello 186(transfers matched)17/46 camlam ancilotti pipe 26mm Dellorto.Ridden many rally miles with this set up,e.g.several c2c plus to the IOW(many times)via the (very hilly)A34 and many other rallies and ride outs.I don,t presume to know better than anybody else.I do know this set up worked for me.

I use an series 2 Li 125 gearbox on my Casa 185 kitted scooter with 18x47 sprockets.I haven't noticed any large jump between any of the gears.First gear is very low but it makes for a very easy clutch life.