Swapping the stock 525 setup to 520 chain/gearing reduces weight and allows for 14, 15, and 16 tooth counter shaft sprockets and rear sprockets are available in sizes from 41 - 52. Another advantage is that 520 chains are significantly less expensive than 525.
A 44t rear sprocket and stock 110 link chain length will allow 14-15t front sprockets to be used.
A 46t rear sprocket and 112 link chain will allow 14-15-16t front sprockets to be used.
A 46t rear is as big as you can go without replacing the rear chain guide.
Front sprockets to use are from pre '96 DR600/650 or any year DR750/800.
JT Sprockets Front:
JTF437 Available teeth numbers in: 14, 15, 16.
JTF438 Available teeth numbers in: 14, 15 (This sprocket has the same 10mm countershaft mating surface as the stock 525 sprocket but will accept a 520 chain, the countershaft mating surface is wider than the JTF437).
The Rear sprockets to use are from a 94-95 DR350-SE/RS or any year RGV250.
JT Sprockets Rear:
Steel JTR822 Available teeth numbers in: 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52
Alloy JTA822 Available teeth numbers in: 44, 45, 48, 49, 50, 51, 52,