On The TrackAfter a solid month of testing, Bones was finally happy with the progress they had made with the new blue flier. I had the pleasure of testing three suspension sets with three settings. All three worked better than stock, but one set worked night-and-day better-it was a big boost of confidence, and the coolest thing about it all was that during one of the days of testing Bones could see a significant improvement in my riding. It's amazing-like a serious kick in the butt-when someone can actually "see" what I'm feeling on the track with the bike! On that day, we were testing at a track with a big, high-speed whoop section. All day I had been using third gear to get through it. After Bones put on the fork and shock that I liked best, I began using fourth gear and was able to carry much more speed. I actually scared myself. The YZ became more predictable and the midstroke plusher. He basically slowed down the midstroke and softened up the last bit of travel, allowing more of the fork to be used before bottoming out. He also made the front end sit a bit higher in the stroke through corners; in stock trim the fork rode fairly low in corners.
One of the main flaws in the stock KYB fork is that it has a bit of negative sag. Most of us would never feel it on the track, but it is still something none of us needs. With the new PC settings, they were able to get rid of it with trick little spacers that Bones designed. The spacers were also one of the ways to get the front end to settle a bit higher in the stroke, a much-needed fix. The shock was also fine-tuned; it tracked nearly perfectly out of corners under acceleration, and I was able to get away with more mistakes through some of the rough sections. The shock really kept the bike straight, even when I would tend to swap; the shock just plain worked! In stock trim the shock was a tad soft and blew through the stroke faster than I liked. The PC crew chose a more-progressive valving and went up one on the spring. Overall, the YZ125 became better balanced, making it easier to ride in rough conditions. As I said before, the new changes were very confidence-inspiring.
The motor just flat-out rips for a 125! The changes to the powerplant make a significant difference over stock. Bottom-end power is a little better, but the mid to top-end power is incredible. That power pulls hard and keeps pulling. This motor doesn't go slightly flat as it did in stock form; there also is a serious dose of pulling overrev. She's definitely a screamer. The best thing about the PC motor is the spot-on jetting. PC selected a 410 main jet, a 375 pilot jet and a stock needle in the third position and set the air screw at 131/44 turns out. The bike never missed a beat; absolutely no bogging down low, and it never once popped while revving to the moon. The motor tweaks were liked by all of our testers. Even our beginner-level riders enjoyed the nice, crisp feeling this motor now offers; the more roll-on power, the easier it is to ride.
This was a huge learning experience for me. I got to see firsthand just how the Pro Circuit team makes a bike that is already good even better. As I said previously, with mass-produced OEM parts, there is always going to be room for improvement, but it takes serious time and resources and, most of all, experience to make these kinds of improvements. The team at Pro Circuit has that, and it was incredible to watch them make components from scratch. The bang for your buck on your original Yamaha YZ125 is amazing, and improving upon that takes a serious investment.