>>28453447
Arguably the fastest man on a dirtbike in 2006 or so was 5'6 (Ricky Carmichael), you'll be fine. Don't worry about putting a new-used engine in a bike, a low stress dual-sport like a DRZ400 would need, at MOST, a valve check + new piston and rings if it really had poor compression and had been ran hard for tens of thousands of miles.