Bill Wood is following the cross-country Motorcycle Cannonball Endurance Run for machines made before 1930 from its beginning September 7 in Newburgh, New York, through its conclusion 3,950 miles later in San Francisco on September 23. Here's his latest report from the road:

The most interesting race in this year's Motorcycle Cannonball Endurance Run is quickly turning out to be the points battle in the smallest class—Class I, for bikes displacing less than 750cc. And it's interesting not because the riders and machines are performing so well, but because each rider is having to overcome the limitations of these smaller bikes in trying to accumulate the most points on the way across the country.

At the beginning of the Cannonball ride last weekend, the top of the standings was dominated by Class I machines, since a large percentage of the bikes finished every mile on the first day of competition, tying them in the overall standings, with the tiebreaker favoring bikes in the smallest class. But on the second day, the organizers offered riders a bailout option that allowed them to skip 60 long miles of congested Cleveland freeways. A few of the Class I riders chose that option, which put them behind Darryl Richman, Michael Wild and Buck Carson, who gambled that riding the freeway miles, while tough on their machines, would pay off in “bonus” miles over their competitors.

Although those Cleveland freeways turned into a disaster area, with competitors facing two total road closures and a detour on the way to the finish line, the three Class I riders who attempted the full route were able to finish all 320 miles, vaulting them into the lead in the Class I and overall standings until each of them suffered problems on the road that prevented them from completing the route on other days. Wild dropped points on every day after Cleveland. Carson suffered engine problems on the hectic 300-mile day leading to a ferry crossing of Lake Michigan. Then Richman's BMW succumbed to a head-gasket failure yesterday on the run from Anamosa to Spirit Lake, Iowa.

That set up an intriguing points battle of a kind not seen in Class II (for 750cc to 1,000cc motorcycles) and Class III (for motorcycles over 1,000cc). In those larger classes, a number of riders remain tied at the top, having finished every one of the 1,649 miles from Newburgh, New York, to tonight's destination: Murdo, South Dakota. As a result, the points standings haven't changed in those classes in days. But in Class I, the struggle to complete long days on the road under sometimes difficult conditions means that the class rankings are different almost every night.

The past two days have provided a perfect look at this class from the sweep truck, as I have witnessed firsthand the challenges riders face in crossing America on these smaller machines that are more than 80 years old.

Two days ago, Darryl Richman still commanded the top positions in the points standings, holding down a perfect score on his 500cc BMW twin. But then, just 7 miles into yesterday's ride, Richman had to pull over and attempt roadside repairs on a leaky head gasket. His efforts to fix the problem weren't successful, and Richman faced a long ride on the sweep truck before he could get to work on his bike last night. Today, his efforts paid off, and Richman was able to complete all 326 miles from Spirit Lake, Iowa, to Murdo, South Dakota, despite on and off rain and some serious uphill and downhill grades once the route entered South Dakota.

Richman's problems yesterday put Italian rider Claudio Femiano into the Class I points lead, with 1,243 miles accumulated when Stage 6 began this morning. But that lead only lasted 77 miles into today's stage, when his 1926 Sunbeam 500 single coasted to a stop with engine troubles. Then it was Femiano's turn to take a long ride in the sweep truck. And he was followed by Michael Wild, whose 1925 Rudge stopped running at 150 miles; Jimmy Allison, who made it 252 miles before his 1926 BSA 500 single made what he described as a very expensive sound; and Jim and Sylvia Crain, riding two-up on a 1927 BSA 500 single, who had to stop at 275 miles after breaking several spokes on the rear wheel.

By the end of the day, that meant I was carrying four of the eight bikes in Class I on the trailer all at the same time. And when we got to the finish in Murdo, we learned that the day's events had moved Buck Carson into the Class I lead, since he had successfully completed the entire 326-mile course, giving him 1,558 miles out of the 1,649-mile total through six days.

The move into first place capped a day of celebration for Carson, since today was also his 21st birthday. He celebrated this evening by doing some maintenance work on his bike.

In other Cannonball news, today nearly saw a major upset in the overall standings, as Steve Barber, who was ranked third at the start of the day, suffered through a tough day on his 1915 Harley-Davidson, the same bike he rode in the 2010 Cannonball.

Barber, who lost the primary-chain cover on his bike yesterday, started out today with a flat tire just a few miles into the course. He was able to repair that in about an hour, but then the bike developed a difficult-to-diagnose engine problem that slowed Barber's usually quick pace on the road. As a result, he ran at the tail end of the field all day, pushing on through the rain on a bike that was significantly down on power. In spite of all that, Barber got to the finish line and held onto his third place in the overall standings.

Also fighting through difficulties was Chris Knoop, the Australian rider who had been touring across America with his wife, Christina, in the sidecar of his 1925 Invincible, powered by a J.A.P. engine. The strain of hauling around the sidecar had taken its toll on the Invincible's clutch and transmission, and the bike had recorded a best finish of just 135 miles yesterday.

Overnight, Knoop made the difficult decision to remove the sidecar and ride the bike solo as a two-wheeler. That meant giving up his hopes of having he and Christina compete in the Cannonball together, but it also took much of the strain off the bike's drivetrain. And that decision paid off, with Knoop riding 326 miles today to record his first stage finish of the competition.

That big day came at a price, though, as the clutch basket on the Invincible broke during the day, causing the rear wheel to lock up. But Knoop was able to make roadside repairs and continue to the finish. The long-term prognosis for the Invincible is uncertain, and Knoop says he can't find a replacement part for the rare Australian machine. So the plan is to roll out tomorrow morning and see if it will hold together for another day.

Other riders weren't as lucky as Barber and Knoop. The longest day of the 2012 Cannonball took its toll on the field, and made for a very busy day for the sweep-truck crew. In all, we responded to 10 calls for bike pickups along the course. Four of those bikes were hauled in by others, but by the end of the day, we still arrived with a full load of six motorcycles on the trailer.

If the trailer was cramped, the inside of the truck was even worse. The sweep truck is one of those short “crew cabs,” with a small back seat. And for the final 50 miles or so, we had six full-size adults crammed into that cab, turning us into a clown-car act when we all piled out at the finish.

One of the notable DNFs was Buzz Kanter, riding a 1929 JDH, powered by Harley's race-replica twin-cam motor. Kanter's JDH is the only example of this rare Harley model in the 2012 Cannonball, but it dropped out today after completing only 57 miles. Kanter was working on the machine tonight, and is expected to be on the starting line in the morning.

That leaves 24 bikes and riders all tied at the top of the standings with 1,649 miles completed. That list includes 12 Harley-Davidsons, eight Hendersons, two Indians, one Excelsior and one BMW. The overall winner of the 2012 Cannonball will almost certainly come out of that group.

Tomorrow, I start with an empty cab and trailer all over again, looking ahead to a scenic 278-mile route from Murdo through the South Dakota Badlands and a stop at Mount Rushmore before finishing in one of America's motorcycling capitals—Sturgis.

I can't wait.