tigerbiker,
Pull off and measure the first 30 feet off the reel, weigh it (you need scales that will weigh to fractions of a gramme) and compare the results with the table - this will tell you your line weight.
AFTM Table
AFTM number
Line no. Grains Grams Ounces
3 100 +/- 6 6.48 0.228
4 120 +/- 6 7.78 0.274
5 140 +/- 6 9.07 0.32
6 160 +/- 8 10.42 0.366
7 185 +/- 8 11.99 0.422
8 210 +/- 8 13.61 0.48
9 240 +/- 10 15.55 0.55
10 280 +/- 10 18.14 0.64
11 330 +/- 12 21.38 0.75
12 380 +/- 12 24.62 0.86
http://www.common-cents.info/part4.pdf gives you all the info you need. ( The gear they suggest is a bit more complicated but the principle is the same !)
Nigel