Don Castro's Streamlined Dirt-Tracker Could Have Changed Everything

Outlaw Justice

Triumph's 750cc twin was the weapon of choice for the 1972 AMA Grand National Championship. Housed in custom steel skeletons built by Trackmaster, Red Line or C&J;, a typical example might weigh 290 pounds and make upwards of 70 horsepower. Don Castro's Red Line-framed Triumph wasn't your typical Triumph 750 flat-tracker. Neither is the story of the birth, death and ultimate resurrection of the bike that could have changed everything.

The kid from Hollister, California, turned Pro at 18, hit the big-time in 1969 and won seven Junior Nationals in his rookie year. Triumph racing boss Pete Coleman was suitably impressed, signing Castro to the factory team in '70. Spectacular talent, hard work and meticulous attention to the mechanical details earned Castro fifth place in his first year as a card-carrying Pro. But as he finished his second Grand National season in ninth, Triumph was sinking in a rapidly rising tide of superior Japanese street machines. Hard times at the home office meant harder times for the race team. Both Castro and Gary Nixon were cut. "That was when I turned privateer," Castro says. "Triumph was bankrupt and we were out on our own."

After a bad start, '72 was about to get worse. "Everything got ripped off while on the way to the Houston Astrodome," Castro says. "I went to Gardena to get some braided brake lines. When I walked back outside, my van was gone, along with my Trackmaster Triumph TT bike and my Montesa. They cleaned me out!" Almost: Castro had a Red Line-framed Triumph in his garage back home that could salvage the season.

By June, Castro had gotten some help from Tracy Nelson of The Fiberglas Works in Santa Cruz, California. The Grand National paddock's artist-in-residence laid up something new for the Triumph, just in time for the Race of Champions half-mile at San Jose. Tracy united the seat, fuel tank and side numberplates in one flowing piece, adapting an aerodynamic pannier-style tank design used by the AJS factory roadracers in the early '50s. "Tracy and I designed it so the air would flow smoother, but we also lowered the center of gravity," Castro says. "All the weight was really low, so handling was perfect." With the fuel riding 6 inches lower than a conventional setup, Castro could tuck in tighter than anyone else. Psychedelic '70s graphics attracted even more attention.

Castro wasn't eligible for the Race of Champions-his first National win as a card-carrying Pro would come a year later on the same track-but he dominated every race he lined up for that day in the slippery new Triumph's first and last appearance. Aerodynamic assistance was against the rules, but the line between a permissible seat/tank/numberplate combination and illegal streamlining seemed open to interpretation until Castro and Tracy crossed it and the AMA officials pronounced the bodywork illegal. The rest of the bike would be fine with the previous conventional setup, but it really didn't matter as Castro had signed to team with Kenny Roberts on Yamahas for '73. "I sold the Triumph to a school teacher who raced it a few times and that was the end of it," he remembers.

The bike could have disappeared after that. Without Don Miller, it probably would have. Miller has been a flat-track fanatic for as long as he can remember. After hitching a ride to the races with his older brothers to watch another Don win one for Team Yamaha, Miller got a shiny new one of his own. He was a Don Castro fan for life.

Fast-forward to the mid-'90s, when Miller meets Castro while writing a story for Old Bike Journal. Castro needs a ride for a vintage race in New York, so Miller rolls out a cool Yamaha. "The year before at the same race Dave Aldana rode my Yamaha and blew it up," says Miller. "I didn't care. I got a bigger and better motor for Don. After the weekend we became good friends. After that, I got Don to part with some of his old racing stuff: a set of his Yamaha leathers and a Bell helmet. He asked if I wanted that old Tracy body. We made a deal and I got the start of this bike. It was useless for racing, so Don lent it to a friend who painted it all one color and used it on a street Triumph. Before selling the bike, he gave it back to Don. One of the coolest racing bodies lay up in Don's attic for years, never to be seen again if I hadn't been pestering him. I compiled a bunch of other parts over the years, but Don didn't know where the rest of the Triumph ended up, so I searched for leads."

About three years ago, Miller's phone rang. "I just talked to Don Castro," said the guy on the other end. "I have what's left of his Red Line-framed Triumph." Miller's heart just about stopped. The guy's dad had the bike. He rode it in some local races, and then parked it. He'd sold the blown-up engine years ago, but aside from a smashed downtube, the frame and swingarm were intact. "I asked Don if he was interested in buying it," the guy told Miller. "He said no, but that I should call you." After checking to make sure he was still breathing, Miller got a price and promised to call back later that day. "I had to check out his story, so I called Don. Everything was legit." Another piece of the puzzle was in Miller's hands.

Putting all those pieces back together the way they were in the summer of '72 was tough. Renowned dirt-track photographer Dan Mahony sent every image he had of the bike, but there weren't many. Mahony remembered the day: It was overcast; not enough sun to shoot color, so everything he had was black-and-white. Texas flat-track historian Bill Milburn authenticated a lot of parts that were on the original bike and found others, including the Carl's Sport Center primary cover. "It took him almost a year to track that one down and a while longer to talk the owner into selling it," Miller says. "I traded a nice Harley Sprint hardtail racing frame for it. Don was also a big help. I would send him pictures as the restoration progressed and he gave me advice along the way."

Looking as outrageous as it did rolling out of Tracy's Santa Cruz shop nearly four decades earlier, the Triumph is currently on display at Miller's Metro Racing headquarters in Brackney, Pennsylvania. "We take it to shows from time to time. I even took it to the Grand National race at Monticello, New York. It was cool to see the new breed of racers stop and have a look at what they would have been riding back in '72," Miller says. "It's a motorcycle that might have changed everything about the sport. And the longer you stand and look, the more you wonder what flat-track might look like today if it had."

Don Castro's Streamlined Dirt-Tracker Could Have Changed Everything
Castro's Barnes knock-off hub is laced to a Borrani WM3 alloy rim wearing Goodyear DT rubber. A right-side rear brake lever cues the Hurst-Airheart master cylinder and caliper.
There are enough things to think about in a 20-lap main event without wondering how many times you've been around San Jose's half-mile oval. Castro's lap counter means no guesswork.
Tom Sifton built the engine, turning the 1972 650cc Bonneville into a 750 with a Sonny Routt big-bore kit, a pair of 76mm ForgedTrue pistons working in the cast-iron block.
Each intake runner carries a 34mm Mikuni carb instead of a 1 3/16-inch Amal. Tracy's contentious bodywork left both carbs and the Filtron foam filters hanging out in the breeze.
Tracy's flowing merger of seat and tank dropped the Triumph's center of mass, making it easier to ride in the corners and allowing rider Don Castro to tuck in tighter on the straights.
Rainy weather put plenty of grip in San Jose's dirt if you knew where to look. Castro, shown here getting around Gary Scott on a conventional Trackmaster Triumph, knew every inch.