The way the schedule's worked out so far this year, we're seven races into the Championship, but we've only had one twins race, at the Springfield Mile. In the early sessions at Springfield, it looked as if -- as many people expected -- the 'metric' bikes would be a real threat to Harley-Davidson's dominance. But, at the end of the day, it was XR-750 powered bikes 1-2-3-4.
If that was how the XRs fared at a track they were expected to be relatively weak at, I can't wait to see how they do next weekend at the Hartford half-mile. After all, popular consensus is that while the import motors' horsepower advantage serves them well on long straightaways, the XR's traction gives them an advantage on the half-miles where bikes are spinning and sliding the whole lap.
Obviously, Grand National Championship mechanics change gearing for the half-miles, but I was curious to know if there were other differences in the 'baseline' setup of an XR-750, between the mile and half-mile tracks. During a lull in the action at the Springfield TT, I cornered one of the very best XR-750 tuners, Kenny Tobert. He's the mastermind behind Chris Carr's machine prep. I asked him about getting ready for the next race, the season's first half-mile.
"The chassis is pretty much the same, but the engine setup is different," Kenny told me. ""On my mile motors, that's where you need a heavy hitter. Something that will pull high gearing all day. But on the half-mile you need something that doesn't hit as hard; you don't need a lot of power, you need something that works. We use a milder engine with less compression and a different cam setting. It's probably not the best of the best, but it's what works."
Taming that power hit is obviously one key to a bike that drives forward as much as possible, instead of uselessly spinning and kicking the bike out too far. So, I asked whether Kenny set Chris' bikes up with heavier cranks for the half-miles.
"I have different weight cranks. Nowadays, with the smaller restrictor plates we're having to run lighter cranks in them most of the time. I got mine trimmed down pretty light," he said. When Kenny and Chris arrive at the track, he's got two different crank weights in Chris' bikes. Chris can try them both and pick the one he likes best. Kenny added, "Most of the time today it's the light flywheel."
I was curious about the differences between the various half-mile tracks. "The half-miles where the setup of the bike is closest to the miles might be the pea-gravel tracks, because they're spinning all the time." he told me. "There, you can run your mile motors, because you want to spin 'em up, like a little tractor pull. You get to Middletown NY in the day time, and you need the slowest of the slow, because it's like riding on a wet bar of soap. It's so slippery you can't get ahold of nothin', so you need a slow one there." [Author's note: Victory Speedway in Middletown is not on this year's schedule, but the red clay track bills itself as the oldest continuously operating dirt track in the country.]
I also wanted to learn whether there were, generally speaking, differences in key chassis setup factors -- such as wheelbase -- between miles and half-miles. Kenny told me that from his perspective, it was track conditions, not track length, that determined chassis setup.
"If it's smooth," he said, "we'll shorten them up to get more bite. But if it's rough, the way it was yesterday [n the pre-soaked and rutted Springfield Mile] we lengthen them out a bit to make it more rider-friendly."
Finally, I asked Kenny what he expected to see in the ongoing battle between the XR-750s and the metric bikes as the season develops. "The metric bikes are strong, but you've got a lot of young riders that are taking time to gel with them. I guess we're lucky that Brian Smith wasn't on that Kawasaki yesterday, because he'd have been tough," he told me, adding, "You get to the half-miles, you're in Harley territory; the Harleys will be dominant. And there's so many young guys going really well; they're hard to pass, so the start's the key. You're going to need to get off line."
I wonder whether any GNC riders have been doing any cross-training at their local dragstrips?