Do you ever wonder how aftermarket companies come up with better settings for your scoot? Every time I go to the track I see bikes that have been fully dressed with suspension, motor work, triple clamps-you name it, and the bikes have it! Big modifications such as these aren't cheap, and with today's bikes near perfect in stock trim, it's getting extremely tough for hop-up companies to improve on the original. I have been asked many times if cost is worth the performance changes and gains. Let's just say it is worth it if the modifications are done right, but it's just as easy to tune your bike into an unridable nightmare.
I spent time with the Pro Circuit crew as they developed settings for the 2005 Yamaha YZ125, and even provided a helping hand on some of their suspension settings. Over the course of almost two months, Pro Circuit put in countless hours of testing cylinder mods on the dyno and on the track, sampling a variety of motor and suspension setups. Because the all-new YZ tiddler was without a doubt one of the best 125s ever born, it wasn't easy coming up with better performance. But as with any OEM part, there will always be room for improvement, however minute; the end result is a nice, fine-tuned machine. But how much greater are the gains in performance, and is it really worth the big bucks?
Tuning The Suspension When a new bike hits the showroom, many think the first step Pro Circuit (PC) takes is opening up the suspension and immediately making changes to the internals, but that is not the case. Lead suspension tech Jim "Bones" Bacon and a crew of test riders head to the track for a few days with the bike in stock trim. Basically, these days are spent getting the stock suspension to work as well as it can. Doing this, Bones can develop stock settings for customers who call in and can't afford to have their suspension modified. He is also able to come up with the numbers for the team's racers who compete in the stock class at all the amateur nationals. Its riders need to have oil levels, spring rates, clicker positions and ride heights. And the main reason Pro Circuit spends so much time testing the stock suspension is to learn the flaws and develop the appropriate remedies.
After reviewing all the feedback from its group of test riders, PC uses the best stock setting as the baseline. Then it takes a second set of suspension and begins modifying the internals. Bones begins with the biggest problems and works his way through the internals, making any changes he sees fit. During this process there is a lot of backtracking, but eventually PC is able to fade out the stock suspension as its modifications work better and better. Through the process the crew will spend their time testing at several tracks.
"Track conditions are always changing," Bones says. "It's really important to take the time at all the different tracks and with a wide range of test riders. It's a time-consuming process, especially with this new YZ125 because the new Kayaba suspension is much better than that of the year before. We have to be thorough during the whole process, and even though we come up with some final modifications, we are constantly monitoring what our customers are saying throughout the year. Every time we get a new bike, I make a spec sheet so I know every part that is inside the suspension. I also create a little sketch with all the dimensions and account for every single part. I will know the length of the fork compressed and extended. I will know when the fork bottoms out, and how much of the inner fork tube will be showing under the dust seal. Knowing all the suspension internals and all the dimensions, I find it's fairly easy to come up with new settings [based on] my knowledge of the components and the feedback from my test riders."