Hi Chinoy....
The Service Manual for the export C5 / E5 / G5 lists the following
Primary ratio 2.15:1
Overall ratio
1st 3.063:1
2nd 2.013:1
3rd 1.522:1
4th 1.212:1
5th 1.00:1
Secondary ratio
2.235:1 / 101 pitch chain ( E5/ G5 )
2.11:1 / 102 pitch chain ( C5 )
The rear tyre is listed as 100/90-19" -57V 3.5x90 ( E5/G5 ), and
110/80-18" - 58V (C5), both with 28PSI, 30PSI with pillion
Other than that, its fairly vague,but I hope the information is of some help to you.