RB20 Gearing

[bennn]

Afternoon all, hoping for a little bit of advice as I've used the 'search' function and not found what I'm looking for.

I'm just running in my freshly built RB20 kit and I'm struggling to get it to pull in 4th gear, 1,2,3rd all fine but I assume I'm dropping too far out of the power for it to keep going from 3rd to 4th.

I'm running AF 46T Road casette clutch, with either 16t or 17t on the front (can't remember) on Spanish Li125 gearbox. Been told an Indian GP200 gearbox will sort my problem as its a shorter gap between 3rd and 4th - but unsure if I'll need to change front sprocket too?

Thanks for any help in advance, Ben.

[Norrie Bodge]

Afternoon all, hoping for a little bit of advice as I've used the 'search' function and not found what I'm looking for.

I'm just running in my freshly built RB20 kit and I'm struggling to get it to pull in 4th gear, 1,2,3rd all fine but I assume I'm dropping too far out of the power for it to keep going from 3rd to 4th.

I'm running AF 46T Road casette clutch, with either 16t or 17t on the front (can't remember) on Spanish Li125 gearbox. Been told an Indian GP200 gearbox will sort my problem as its a shorter gap between 3rd and 4th - but unsure if I'll need to change front sprocket too?

Thanks for any help in advance, Ben.

18x46 on Indian GP200 gearing
What pipe you using ?

[bennn]

Chiselspeed ADS Fast Road.

Thanks, Ben.

[dscscotty]

18x47@5.22 with chisel pipe-

[bennn]

Thanks, would it be OK at 18x46 or not?

Thanks, Ben.

[Norrie Bodge]

Thanks, would it be OK at 18x46 or not?

Thanks, Ben.

Try it m8, b4 you go buying a 47 cassette crownwheel

[bazza3004]

15/46 on Li 150 box

[bennn]

Conflicting views then, any benifit to one 'box over the other?

[hullygully]

LI150 would give you closer ratios in ALL gears
unlike the GP200 (either Italian or Indian) were you get a long-ish gap between 3rd & 4th

[bennn]

And I'd be able to keep the 46T clutch? Had a look at changing to a 47T £80

Li150 give decent top end too for cruising?

Thanks, Ben.

[al pushpak]

Indian gp 200 gearing has a SHORTER gap between 3rd & 4th compared to the gp 200 Italian box, I have one in my ts 225 & it pulls fine

[hullygully]

aye but LI150 has even shorter gap
used both plus SX200 in TS1's

[martyn dwane]

Li125 box with 46/16 sprockets is 5.3 o/all. same box with 46/17 is 4.98.
id check what sprockets your running before buying any new box.
down load the excellent
Lambretta Gearbox Visualiser by Avatone, very useful shows % rise betwwen gears and you can compare different gearboxes sids by side.

[hullygully]

+1

[al pushpak]

Whatever works for you mate , GP 200 gearing suits my set up as its quite hilly where I live

[bennn]

I wonder if it's a 17t then, I seem to remember looking at a gearbox visualiser before I built it and final drive working out at 4.9 ish.

[holty]

so your gearbox will not pull 4th as you cannot go fast enough in 3rd to get on the pipe in 4th, as suggested a gearbox with a closer 3rd to 4th ratio will help, I know the indian Vijay 150 mk1 gearbox has a smaller jump between 3 and 4 than the gp200 gearbox, this might enable you to keep the same front and rear sprockets and chain etc that your using now, and they come up on ebay now and again for not much money, your exhaust choice plays a massive part in drive ratio and gearbox selection, what exhaust have you got ? that been said the rb20 is meant to rev and rev so over gearing it will ruin the riding experience, maybe just fit a 16 front and a pull down tensioner and give it a try, you might just find it will ride much better, they are designed to rev high in each gear, and see if it pulls top gear ok, could be the easy/ cheap fix.

[bennn]

Thats right Holty I'm using the Chiselspeed ADS Fast Road, I can get it into the power in 4th if its slightly downhill a tailwind or I absoloutely spank it on the flat.

Think I'm just gonna go for the Indian GP200 box (a mate has one) and just change front sprocket to 18T and chain to suit and see what it's like at that, hopefully shouldn't be too costly

[Norrie Bodge]

Thats right Holty I'm using the Chiselspeed ADS Fast Road, I can get it into the power in 4th if its slightly downhill a tailwind or I absoloutely spank it on the flat.

Think I'm just gonna go for the Indian GP200 box (a mate has one) and just change front sprocket to 18T and chain to suit and see what it's like at that, hopefully shouldn't be too costly

[holty]

pretty sure ive read somewhere that the Spanish li125 box has a massive gap between 3rd and 4th gear so a gp200 should make getting it pulling in 4th easier.