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mikeracha

Gearbox "customizing?"

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I opened up the chaincase on my Series 2 today to see if there was anything other than worn corks that needed attention. I found that my gear cluster roller bearing had failed and the rollers were long gone and the end of the gear cluster is badly worn and needs to be replaced. (Side note: I'm amazed at how well this gearbox worked without that bearing. I'm pretty sure it failed months or even years ago.) The motor is an Indian GP200 case with a GP primary, Li125 gearbox, GBM RT225, 60/110 crank, one of the new and improved big box clubman exhausts and a Delly 28mm carburetor.

I have a complete Indian GP200 box, a Spanish LI150 cluster, and a handful of loose gears in my stash. I hated the GP200 gearbox when I had it on this motor so don't want to go back to it. How interchangeable are the pieces of Lambretta gearboxes? How much mixing and matching can one do, if any? Or should I just plunk down the cash and get the new Li150 gearbox and call it a day?

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I think you are better off getting a 150 gearbox, but if you want to experiment, casually looking at close ratio gearbox numbers the trees seem to be 

11, 14, 16, 18. Loose gears are li 150 1st 50, li150 2nd 41, li125 3rd 39 and a gp200 4th 36 on 18, 47 sprockets.

I have also seen 13, 15, 17, 19 tree with  47, 40, 37, 35 loose gears. Dont know the sprockets used.  

So using what you have: li150 1st and second, li125 3rd and a gp 4th would be interesting.  You will have to look at the numbers and try to get to around the numbers listed. I have never mixed gears from different bikes, dont know if any of it will work. I have used close ratio boxes with trees and loose gears manufactured to be used together. Also, serveta gearboxes are said to be weak. 

 

I find this sight simple and helpful

http://www.scooterhelp.com/tuning/lam.gear.calc.html

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Most of it will come down to if the loose gear fits with the tree gear. Getting the ratios worked out is easy. (L#/T#)(R#/F#)=Ratio {L= Loose gear, T=tree gear, R=Rear sprocket, F=Front sprocket}

I know MBD does a bearing to fix the tree gear and I think he put out a book covering all the possible gearing combinations.

Personally I'm a fan of the GP200 and LI125 gear boxes. They are good platforms for finding that perfect ratio.

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yeah i would rock the 125 gearing with GP sprockets. should give you 4.8 final drive

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28 minutes ago, DerekM said:

yeah i would rock the 125 gearing with GP sprockets. should give you 4.8 final drive

Yes. I have been running that for years and put one on my son's bike too. It is a nice set up. I wish I hadn't fekked it up. :( My other son runs Li150 gearing with GP sprockets on a similar build and likes it a lot.

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