Gear Compatibility

[R_Andersen]

Hi all, i have a '64 LI 125 and need to replace the gear cluster and 3rd gear but I'm having trouble finding parts.

Is it possible to replace the full set of 4 free gears and the gear cluster with a set from a different model Lambretta, such as an LI 150 gearset or something similar? These seem much more available and the gear ratios are similar.

I'm just not sure how interchangeable the gears are from the different models as long as I replace all of the gears together?

Thanks,
Rob

[Toddy]

Gear boxes are interchangeable but you may need to change sprockets to get the correct final drive below helps

http://www.afrayspeed.co.uk/pages/45-to ... -chart.xls

[HxPaul]

If you change the cluster and the 4 gears,theres no problem.Some of the loose gears are interchangable,but not all.If you change the gearbox,stay with the cluster and 4 gears and you wont go wrong.

[Minority]

Just be aware that the shimming may be different and that there is a considerable difference in the final drive ratio between the LI125 and the LI150. Dropping the front sprocket from 15 to 14 will give a closer match, but then you will have to consider using a pull down chain tensioner.

[leigh]

Sure I have 125 cluster in my garage.

Leigh

[johnny650]

thats a great chart calculator that toddy posted. I spend hours calculating different gear ratios . I think its a hang over from my cycling days when we only had 7-8 gears on a cassette and had to avoid big jumps between gears .

Something that has intrigued me is the 1x tooth difference you sometimes see between loose gear sets and their identical gear clusters (christmas tree ) of the various models .

if you compare first gear with its companion first gear of the gear cluster you see that first gear is either 50T or 51T right through the whole Lambretta model range (except TV models ).

If you look at the opposing gear on the gear cluster it can vary by 1x tooth . So you can have 50-11 on the Li150S Pacemaker for example and 50-10 on the Li125S and GP200 models !.?

There are examples of this throughout the gear ranges of all models so I presume that there is sufficient tolerance in the teeth geometry that you can go 1x tooth up or down when building your gear set from scratch.

If you look at the the Li150S pacemaker , the Li125 and the Li125S models you'll see that the 39T loose third gear will work with a gear cluster having a 17T , 16T and a 15T sprocket on the gear clusters interesting eh ?http://beedspeed.com/html-pages/Lambret ... oChart.htm

[Fruitjuice]

If you look at the opposing gear on the gear cluster it can vary by 1x tooth . So you can have 50-11 on the Li150S Pacemaker for example and 50-10 on the Li125S and GP200 models !.?

There are examples of this throughout the gear ranges of all models so I presume that there is sufficient tolerance in the teeth geometry that you can go 1x tooth up or down when building your gear set from scratch.
?http://beedspeed.com/html-pages/Lambret ... oChart.htm

So basically if I have an Italian Li150 gearbox I should be able to replace the loose 37T third gear with a 387T one from a late Indian GP200 or Vijay Super GP150 to reduce the gap between third and fourth.... interesting...

[Minority]

If you look at the opposing gear on the gear cluster it can vary by 1x tooth . So you can have 50-11 on the Li150S Pacemaker for example and 50-10 on the Li125S and GP200 models !.?

There are examples of this throughout the gear ranges of all models so I presume that there is sufficient tolerance in the teeth geometry that you can go 1x tooth up or down when building your gear set from scratch.
?http://beedspeed.com/html-pages/Lambret ... oChart.htm

So basically if I have an Italian Li150 gearbox I should be able to replace the loose 37T third gear with a 387T one from a late Indian GP200 or Vijay Super GP150 to reduce the gap between third and fourth.... interesting...

I think that's a very dangerous assumption to make. It's not just number of teeth, but diameters etc that come into play when matching gears to clusters.

[johnny650]

If you look at the opposing gear on the gear cluster it can vary by 1x tooth . So you can have 50-11 on the Li150S Pacemaker for example and 50-10 on the Li125S and GP200 models !.?

There are examples of this throughout the gear ranges of all models so I presume that there is sufficient tolerance in the teeth geometry that you can go 1x tooth up or down when building your gear set from scratch.
?http://beedspeed.com/html-pages/Lambret ... oChart.htm

So basically if I have an Italian Li150 gearbox I should be able to replace the loose 37T third gear with a 387T one from a late Indian GP200 or Vijay Super GP150 to reduce the gap between third and fourth.... interesting...

I think that's a very dangerous assumption to make. It's not just number of teeth, but diameters etc that come into play when matching gears to clusters.

thats an interesting assertion .........

What evidence, if any, do you have to support that assumption ?

[Doom Patrol]

I once heard about someone who fitted the 3rd gear from a Spanish LI in an Italian gearbox. It apparently jammed owing to the fact that the Spanish gear was thicker.