Since 1992, Kevin Brooks-the main man behind Thunder Mountain Motor Sports (TMMS)-has been building every flavor of all things motor; from competition boats, cars, and bikes to snowmobiles. For the past few years, the TMMS crew has garnered accolades in bike shows across the country, competing against and beating the big boys. His Best of Show bike from the '05 Laughlin River Run, Sinful, graced the cover of the March '06 STREET CHOPPER. Kevin and his friend and painter, Longhair Billy, tirelessly tear up the show circuit in their custom big-rig. They don't have a personal driver, or a Hummer, or scantily clad women to attract attention to their booth. They don't need it; instead they do it humbly with hard work, along with the help of Kevin's cool kids, and let their bikes do the talking.
A year or so ago, Kevin came across a wrecked '97 Sportster. Other than the 1200cc motor, the bike was pretty much toast-garbage in most people's eyes. He got out the Sawzall and salvaged the neck to preserve the H-D numbers that matched the motor. Instead of just building a budget scoot and bolting on some parts, he decided to go big. That's how he rolls. He wanted to run a dual runner intake with some Holley 94 carbs that came from a Bonneville car racing effort. To do this would require completely reworking the heads on the Sporty.
Reminiscent of the famed XR-1000, Kevin utilized two rear Sportster heads to get the intakes to both face forward. Sounds easy, huh? Well, apparently it's never been done before; the experts said it couldn't be done. The first step was welding closed the pushrod holes and then machining in new ones to accommodate the rear head being installed on the front jug. Modifications had to be made to the rocker arms, the length of the pushrods, and the tubes also. Ahh, almost done. Well, not quite. The cams were another whole issue that Kevin had to work out. For this motor to run, the front intake and exhaust cams had to be switched, but you can't just swap the cams and call it a day. He used the rear cam's timing as a reference to measure, with a degree wheel, when the valves opened and closed. Using this information, he was able to transfer that info to the front cams to achieve perfect cam timing.
'50s-era Maund velocity stacks were added on to the hand built chromed intake manifolds. Spent gasses exit the mill through a set of custom pipes that were made to resemble hot rod Laker car headers. The entire motor was polished and refilled with H-D and Screamin' Eagle parts before putting it into the custom frame. Starting with the H-D neck, Kevin added a single twisted downtube to the frame. It started as a 1-1/2-inch solid square stock that was heated with oxygen/propane to get the metal soft enough to twist. Kevin explained that the propane mix gives a deeper, more consistent heat than using acetylene, and resists cracking. Continuing back with the frame, he stretched the rear end out 12 inches allowing a super low seat area.