From what Ive read the Seca II sounds like a great first bike. Its a nice 4 cylinder carborated bike. Ive thumb through several pages and they all rank it as a great beginner & intermediate bike. It also seems to have been pretty popular back in its day, so unlike my bike, you will be able to find all the parts you might need.
Exerpt from Total Motorcycle.com
"The Seca II was Yamaha's entry in the 'bargain motorcycles' sector. When it first came out, its competition was the Kawasaki EX500, the Bandit 400, and the GS500E. It had many advantages over all of them. The motor was based on the Diversion 400 motor used elsewhere in the world. It was put in a full size steel tube frame. The Seca was a stylish motorcycle, and performed very well. It was comfortable, simple to work on, and a decent performer. The two valve per cylinder engine was no technological marvel, but it was reliable and easy to live with. The half fairing did a good job of protecting the rider from the elements. The Seca II was a very well rounded package. If a new Seca II's price is a best buy, then buying an old version of the exact same machine for less should earn the buyer a place in the bargain-hunter's hall of fame. Power in 1992 was 49.1bhp, with torque of 35.4ft/lb's. Wet weight was 450lb's."
Welcome to Sport Bike World,