As the owner of Gateway Thunder Hot Bike/Street Chopper of St. Louis, Greg Kottmann sees cool-looking bikes roll out of his shop on a daily basis. He especially sees lots of Big Dogs, since his shop specializes in customizing them. Greg has always liked the styling and design of the production bikes. However, there is one model that he is particularly fond of - the Pit Bull. One day, as he was admiring the rigid stature of one of the Pitbulls on his showroom floor, he thought about using the bike as the basis for a custom chopper. Within minutes, Greg's thoughts became actions, and he rode the Pitbull over to his other shop, Astech Machine, for some extensive fabrication.
In order to turn the Pitbull into a radical chopper, it needed chopper dimensions. The bike was stripped down to the frame, and then 7 inches were added to the downtubes along with another 1-1/2 inches in the backbone, taking the neck rake out from its original 36 degrees to 38 degrees. The only suspension for the bike comes from a set of Forking By Frank's 9-inch-over tubes in Big Dog lowers, held in place by Astech triple-trees.
The bike rolls on a custom set of spinner wheels that were inspired by the new trend in the automotive industry. They look like ordinary wheels except they have a center split so that the right-side outer-half spins separate from the hub. When the bike comes to a stop, the free spinning section is still moving. To expand on the idea, Greg designed the wheels so that the free spinning section can be locked in position while the wheels are moving, which gives the illusion that the bike is sliding across the surface. The front of the bike is held up by a 21-inch wheel wrapped in Avon rubber, while out back an 18-incher is covered in a stout 250. Stopping is made possible with P.M. calipers and rotors, with the rear wheel using a drive-side conversion.
Now that he had a rolling chassis, it was time for Greg to put the original 107ci S&S motor back in between the framerails. Before the motor was set in place, Greg had the heads ported by Ron's Porting, and then to dress it up a bit while it was apart, he sent it over to Arkansas Jim for polishing. When the parts came back from polishing, it was secured to the frame, and then an S&S Super G carb was added, along with a Force Winder air cleaner and a Thunderheart single-fire ignition. Greg wanted a cool set of pipes that would really catch people's attention, so he left the task up to Joe Zwerlein, one of his Gateway Thunder employees. What he came up with was a set of pipes that sweep down towards the rear of the bike, then immediately make a 90-degree turn behind the transmission, and end in a slash cut just behind the primary.
The power created by the motor is transferred to the rear wheel via a Baker six-speed transmission in a TP case, along with a Rivera clutch and a chain primary drive. Greg wanted to incorporate some old-school style into this modern chopper, so he had his Astech crew modify the clutch by installing their Juice Foot Clutch and a jockey shift.
The next order of business for the chopper was sheetmetal. Greg was completely happy with the stock fenders and oil bag that came on the Pit Bull, so they were pulled from the shelf and bolted back on the bike. The only modification that Astech made was fabricating a pair of fender struts to reinforce the rear fender. To help accentuate the chopper look that Greg was going for, a WCC gas tank was acquired. The tank was stretched to meet the front of the seat, and mounted to sit high on the frame.