Scooterotica

i have a cast iron barrelled 240 , indian gp 200 gearing, its running great , fly's in 1st ,2nd,3rd , pull's well in fourth but never reaches the power band in fourth and takes a while to build up decent speed, it cruises at 60 and will go down to 30 without have to change down it responds well to throttle, to get it to rev better in fourth should i change gearbox and rear sprocket to li 150 type or change the front sprocket, if so do i go for larger or smaller front sprocket thanks.

Quick answer: drop the gearing = smaller front sprocket or change the exhaust to one that has better low rpm torque. (Pull-down chain tensioner or different chain required for down gear)

The 240 'should' however not struggle with that gearing = more info about your set-up required (rider weight optional)

i wouldn't say its struggling , just not as peppy as the first three gears , no im not a larry large , about 13 stone , its running a jl 3 which is revvy , carb is a 34 amil and im very happy with it , i might try a 19 front sprocket and see how it is, thanks .

Well, GP200 gearing is already pretty low at 5.22 final drive and at 60mph you will be doing about 6200rpm which should be well in the powerband of a JL3 exhaust. I would think with a 240 and JL3 you should already have reasonable low down torque (backed up by the fact that you say it will pull smoothly away from 30mph in 4th). The Indian GP200 gearbox has a nice small gap between 3rd and 4th so you're not likely to drop out of the power band (the gap between 2nd and 3rd is much bigger and is where it needs the extra revs)
Do you know the porting specs?

what front and rear gearing are you running ?