The new generation of suspension that comes on the 2005 YZ250 is the best we have ever seen from Kayaba. However, the more time I put on the stock suspension of our '05 YZ250, the softer it became, and I thought it could be significantly better with some focused attention. So I ripped the suspension off the blue 250 and sent it to the boys at Independent Race Shop (IRS) in Central California.
In stock trim, the suspension is a tad harsh in rough conditions. The last part of the stroke on the fork is too progressive and left me thinking I had bottomed out when I hadn't. I also didn't like how low the fork settled in low-speed, tight corners. It used up too much of the stroke. As for the shock, it wasn't all that bad, other than being a bit soft on flat landings. It was the opposite of the fork, as it was not progressive enough, though this was hardly noticeable.
| Independent Race Shop | 805/544-9531
www.independentraceshop.com |
| Hard Parts | Max. | Rated |
| Turnaround | 20 | N/A |
| Function | 50 | 49 |
| Durability | 10 | 10 |
| Design | 10 | 10 |
| Price | 10 | 10 |
| Total | 100 | 79 |
IRS replaced the stock 0.43kg/mm springs with 0.44kg/mm units along with easing up on the valving. IRS went up 2 in the shock's spring rate, from 4.9 to 5.3kg/mm. Once the work was done, the IRS mods were tested at a very rough Glen Helen. I set the rear ride height at 105mm and dropped the fork tubes down to the bottom lines. The IRS modifications worked well; I now had what I desired. The bike sat higher in the stroke when cornering, and the fork wasn't too harsh at the bottom. I was able to use all of the fork travel. The biggest difference was the jarring sensation when I nearly bottomed on the fork was completely gone, and the fork was much more predictable. The 5.3 shock spring was too much; so we replaced it with a 5.1, which worked great for me; now the shock was very compliant and soaked up anything thrown at it.
Overall, the bike felt much more balanced; the front end no longer felt low, and I liked how predictable both the shock and the fork were with the new valving and spring rates. The complete customized suspension modification cost $575, and IRS did a great job. If you're a serious racer, you'll find the IRS crew provides trackside support at nearly all the big amateur nationals.
Corey Neuer