BEST OF JODY’S BOX: THE MXA TEST PROTOCOL OF ONE BIKE FROM START TO FINISH

People always have lots of questions about the inner workings of what an MXA test rider actually does for his cash. I can’t speak for other test riders, but here is a brief synopsis of my life with one bike from the past—the 2007 KTM 450SXF.

Every bike test starts with a tech briefing and the KTM 450SXF was no different. Well, this one was was a little different because KTM’s Tom Moen brought along a head honcho from the Austrian factory to help with the product introduction. As always, testing starts with a thorough run-down of all the new features. The briefings almost always carry over into lunch, but this one ended with me taking the Austrian up for the full aerobatic circuit over the Pacific Ocean in my Varga VG-21 airplane. It’s amazing the information you can get out of corporate vice president when you’re diving at the ocean at 140 mph!

After the tech briefing and flying lessons, the MXA gang took the 450SXF to MXA’s studio for principle photography and to SoCal’s Gorman motocross track for the first of many test sessions. Once the SXF was broken in, we were ready to begin the cycle of dyno, track and race testing.

On the dyno the KTM 450SXF made four more horsepower than the 2006 450SXF. The dyno curve was a soft on the bottom, but strong on top (with phenomenal over-rev). The dyno chart was intriguing, but virtually meaningless without track time. In a shakedown run, three MXA test riders went to Glen Helen to discover what changes we’d need to make before we raced it on the weekend. By the end of the day we had a wish list of stiffer forks, new shock spring, lower gearing, richer pilot jet and an exhaust system with a smaller head pipe.

I TOOK THE KTM ENGINE DRAWINGS TO A FORMER TEST ENGINEER AT TOYOTA RACING & DEVELOPMENT AND HAD HIM EXPLAIN “FINGER FOLLOWERS” TO ME. HE EXPLAINED IT IN GREAT DETAIL, I ABSORBED ONE-TENTH OF WHAT HE SAID.

That afternoon, I went to Pro Circuit and asked them to build me a prototype exhaust system; Mitch was out of town, so I just told them to wing the specs, but that I needed a smaller head pipe to help pick up the low-to-mid transition. I gave them 24 hours before I’d be back to dyno the new pipe. In the mean time I called KTM’s Tom Moen and arranged to meet him at Glen Helen a day later. I told him that I needed stiffer forks, lower gearing, stiffer shock spring and richer pilot. While I was waiting for the pipe, I took the KTM engine drawings to a former test engineer at Toyota Racing & Development and had him explain “finger followers” to me. He explained it in great detail, I absorbed one-tenth of what he said.

True to their word, Pro Circuit had the pipe ready for the dyno within 24 hours (although we are talking fairly late in the night). The prototype pipe made two more horsepower at peak and was four horsepower better than the stocker from 10,000 rpm on. Curiously, it wasn’t all that much better than the stocker below 7500 rpm—I was excited about the extra ponies, but confused about why my smaller diameter head pipe idea had resulted in more top-end power. Oh well, I guess my career as a four-stroke exhaust pipe designer will have to be put on hold.

The next day, the 2007 MXA test crew of Tim Olson, Willy Musgrave, John Basher and I met KTM’s Tom Moen at Glen Helen. At first we rode the bike in its most recent test interpretation to establish baselines before slowly, over the next eight hours, changing one part at a time. KTM didn’t have stiffer fork springs, and since the WP fork was totally new for 2007 neither did anyone else. On a whim we decided to make the forks stiffer by increasing the nitrogen pressure in the SXS bladder. It was an off-the-wall solution that wouldn’t work on any other fork on the planet, but after several clicker settings and oil heights we found what we were looking for (although we would return a few days later with stiffer forks springs and undo everything we tested).

We moved to the shock, swapping the soft 6.6 kg/mm spring for KTM’s only optional spring, a rather stout 6.9. It was our only spring choice. It didn’t work. We tried every high-speed, low-speed and rebound setting possible and gave up before we had a test rider revolt. Returning to the 6.6, we started all over. It was a compromise, but one that we would revisit later with a 6.7 (undoing all that we did one more time).

THE DYNO CHART HAD BEEN PROMISING, BUT FOUR MORE HORSEPOWER AT 11,000 RPM JUST WASN’T IN THE SWEET SPOT. MAKING A 50-PLUS HORSEPOWER BIKE FASTER ON TOP DOESN’T TRANSLATE ON THE TRACK.

Once we exhausted our suspension possibilities with Tom Moen, we put my last-minute exhaust system on the 450SXF. The dyno chart had been promising, but four more horsepower at 11,000 just wasn’t in the sweet spot. Making a 50-plus horsepower bike faster on top doesn’t translate on the track. We junked the pipe and within three days I had two more prototype pipes built; only this time I went for not only a small diameter head pipe but a much longer overall lengths. Oh yeah, this time I sought competent help from famous pipe builders Mitch Payton and Doug Dubach. This was a symbiotic relationship: They were helping me fix what I perceived as a problem and they were getting to test exhaust systems on a bike that wasn’t for sale yet. In the end, I would end up testing six different pipes before finding a combination that I liked (I don’t know how many they made before handing them over to me).

Two days later, the MXA wrecking crew raced the 450SXF in three different classes with three different test riders and, in between, we let every KTM rider we knew take a spin on it to get their feedback). Each race resulted in uncommon problems and unique solutions—and we kept racing it week in and week out.

The process above ate up two months. In that span of time I torn the forks down to mix-and-match the fork springs with Showa’s and Kayaba’s wide assortment, had the 450SXF on the dyno at least ten more times, raced it (or assigned it to another test rider to race) every weekend, driven Tom Moen crazy with technical questions, tested everything from Bridgestone to Pirelli to Dunlop tires, set the race sag at every increment from 95mm to 112mm (settling on 105mm) and written a ream of test reports in my notebook (every ride ends in paper work). And eventually wrote the finished bike test as it appeared in the November 2006 issue of  MXA.

The 2007 KTM 450SXF.

Oh yeah, I guess I failed to mention that at the same time that I was testing the KTM 450SXF, the rest of the MXA test crew was doing the exact same test protocol for the 2007 Yamaha YZ125, Suzuki RM250, Honda CRF250 and then-secret Honda CRF150 minicycle.

That, in a nutshell, is the life of an MXA test pilot.