At 12 oz. to 5 gal. your at something like 55:1, definetly nowhere near 20:1.
3 oz. to a gal. is 45:1 and 3.2 oz. to a gal. is 40:1.
I run my '98 KTM 300 EXC at 40:1. I live in Ohio, about 300-1400' above sea level, temp ranges from 50-90 degrees F during my riding season, here is my jetting: 172 main jet, 42 pilot jet, N85D needle in the 2nd clip position from the top, 1.5 turns out from fully seated on the air screw.
Not much difference from '97 to '98. Go to
www.holeshotktm.com, click on message board, click on jetting forum, and there you go, more jetting info for KTM than you can shake a stick at !
Do you have your owner's manual ? There is a good section in it on jetting.
Brian