The Mile tracks are still dominated by Harley-Davidson XR-750s, and the half-miles are utterly dominated by them. So how is it that a motor designed over 40 years ago stays competitive against far more modern engines? The question's even more interesting when you consider that XRs compete under rules that are literally more restricted - AMA Pro Racing's technical rules insist that as purpose-built racing motors (as opposed to motors pulled from production street bikes) the Harleys' intakes include a 32mm restrictor plate.
One team that clearly hasn't been too hampered by their bike's ancient two-valve, pushrod architecture and those restrictor plates is Zanotti Racing. Their XR-750s were fast enough to win Jake Johnson the championship last year.
Motion Pro is one of Zanotti's sponsors. Motion Pro's Chris Van Andel, who has a keen eye for trick parts, recently told me, "If you take a good close look at Zanotti's XRs, you'll see they're full of unique components they make themselves." Van Andel raved about the amount of high-tech effort the team's put into extracting as much power out of the Harley twin, while building in as much reliability as possible.
I didn't expect Dave Zanotti to tell me all (or really any) of his secrets, but I still thought he'd be a good place to start, in terms of learning what it takes to win a championship with a motor that's decades older than the guy riding the bike. Read to the bottom to get a hilarious perspective how Dave, as a team owner, thinks of his rider as a stray dog...
"In past years, we had to run 33mm restrictor plates on the miles, and we could run wide open on the half-miles," Dave told me. " Now, we have to run 32mm restrictor plates - that's to allow other bikes to be competitive with the XR-750. We lost about 5 horsepower going from 33mm to 32mm, but you have to keep in mind that the carb is a 38mm, so in total, the restrictor plate probably costs us 15 horsepower."
In order to get some of that horsepower back, Zanotti is pushing his XR-750s to higher and higher redlines. The bikes he's building for Jake Johnson rev at least 1,500 rpm higher than the XR-750s Dave's dad fielded for Steve Eklund back in the '70s.
Dave pays a price to rev those old pushrod motors so hard. The cases crack around the main bearing journals, and rod bearings - which, brace yourself, cost $1,000 a piece - heat up and fail. Whereas motors used to last a few races between major rebuilds, Zanotti Racing now has to inspect them thoroughly after every race.
As Dave bemoaned the amount of work - and the parts budget - needed to keep an XR-750 competitive, I asked him if he ever considered switching to a rival brand. "Oh, every day!" he replied. "We could buy a Japanese motor in a crate for a tenth of what we pay for a XR motor. And when you take delivery of an XR motor, it comes in a 5' x 5' x 2' crate. Every part is in an envelope. You have to send the heads out for work and the cylinders out to get nikasil-treated, and you have to assemble it from scratch."
There's subtle differences in tuning philosophies among top builders. It seems that the smaller restrictor plates have caused oversized valves to fall out of vogue a little. Compression ratios vary. Dave told me that although they like to stay in the 10:1-11:1 range, he's heard of people running as high as 14:1. While no one wants to share the intimate details of their XR builds, he described Zanotti Racing's approach in general terms. Basically, his goal is to lighten internals a bit to allow the motor to spin to higher rpm without shaking itself apart. The team never stops looking for any tiny advantage.
"I have an environmental company," Dave told me. "But every day, I'll be driving out to a work site or sitting in a meeting with clients, thinking about tweaking a PVL ignition to get a hotter spark, or trying different exhaust cones.
Mostly though, Zanotti's preparation philosophy recognizes that to finish first, you have to first finish. "My mechanic is just so finicky," he told me. "If other teams realized how much attention to detail we put into preparing for every race... I don't think they'd do it; I think they'd all change brands."
What keeps Zanotti in the Harley-Davidson camp - at least for the foreseeable future - is that after all the expense and hassle in the engine room, XR-powered bikes still out-handle all their rivals on the track. Dave thinks it's down to the heavy old crankshaft being located so close to the front wheel that bikes can keep weight on the front and steer better through the turns. And the Harley's been so dominant for so long that the people who prepare tracks basically define a good track as one that's good for Harleys.
"Other motors probably have 20 more horsepower, but if you can't put it to the ground, it's not going to do you any good," Dave told me. "Jake said, when he got to the Kawasaki at Springfield he couldn't stay in the draft. When Henry was on the Aprilia, you couldn't draft it, either." But while he'd love to deliver that kind of power to Jake, he knows they'd spend the next two or three years struggling to put any other brand of motor into a package that would handle, especially on the slippery half-miles.
So instead of spending pennies on the dollar, and buying more power and reliability, Zanotti Racing will spend thousands of dollars and hundreds of hours preparing Jake's XR-750 for Springfield, where it will run just about wide open, non-stop, for 25 miles... if they're lucky.
"We put so much time into this," Dave told me as our conversation was coming to a close. "None of us get paid, and maybe that's part of our success. We don't have to do it, we want to do it."
Then he mixed a funny metaphor, making a statement that both made me smile and think, 'This is why I'm a journalist.'
"When you have a rider that steps up, it's like a dog that steps up on your porch," Dave told me. "Once you feed it, you have to keep feeding it, because he's going to come back. When someone starts depending on you, you have to follow through. We feel that we have to work to our full potential, because our rider's giving us his full potential."
Finally - and I think he was talking about a race team, but it also applies to that big crate of parts you get from Harley-Davidson when you order a new XR-750 motor - Dave said, "When it all comes together, it's a beautiful thing."
Không có nhận xét nào:
Đăng nhận xét