It was at Ascot, in the 1960s where one racer got the advantage by hardening the venerable Pirelli 4:00X19 MT53. He and a few other riders figured out the older tires they previously used, worked well because they were really hard. So hard, in fact, you had to use a grinder to “cut” the tires. When they ran out of those old tires, top Ascot rider, Johnny Gibson, put tires on the roof of his house to bake in the southern California sun. Later, he treated the tires with a hardening compound and placed them in a tire recapping mold to heat them up. After the “heat treating”, the tire lasted longer and gripped better. Riders used razor blades to cut the tread, for traction both in the front, and rear. Cutting the tread, even between races, allowing for a fresh edge and more traction. Later, tire technology improved, and riders no longer had to heat the tires up, but top tuners even cut the newly designed tries to keep a fresh edge. 

In the ‘60s, Ray Hensley was working at Kolbe Honda in the San Fernando Valley (west of Los Angles) and modified a stock Honda CB250 frame for a local flat tracker who raced at Ascot. Ray, as with most racers at the time, believed flat trackers should have a rigid rear section, so he cut off the rear of the stock Honda swing arm frame and fabricated a hardtail. Later, Ray teamed up with Kenny Watkins. Watkins had a fabrication and machine shop called Sonic Weld. 

Linn Kastan worked at Sonic Weld and was a self-taught master welder. Together, they built the first flat track-specific frame in 1968. The first Sonic Weld frame was made of 4130 chrome-moly, it was light and became very popular, especially among the 1968 Ascot Pro novices running 250cc machines. Most of the Sonic Weld frames produced were nickel-plated and looked really good. Then later, they built a complete 4130 swing arm frame. The first one was for a Triumph 500 and went to Gary Nixon. 

During this period, Hensley moved his production to another location and took Kastan with him to form Trackmaster Racing frames. The timing was good for Trackmaster because, at the same time, Junior and Expert engine displacement went from 500cc OHV to 750cc. The rule change caused a flurry of activity for racers nationwide to get ready for the new season. They had to build an all-new flat tracker based on the new rules. Trackmaster was perfectly positioned to provide the ultimate flat-track chassis and did so with the first purpose-built, dirt track racing frame. Initially, Trackmaster frames were available “frame only” or with all the necessary hardware for assembly. 

Later one could get a tank, seat, fender brace, forks, and pegs/brake pedal all designed to fit perfectly on a Trackmaster frame.  Triumph offered many performance engine parts and factory racing recommendations/ specifications, including a drop-on 750cc top end kit, for the 650 unit engine. Other specialty performance companies (WEBCO, Megacycle, Barnett, ARD, etc.) had many proven performance parts and accessories for the Triumph 650. Combined with the Trackmaster frame “kit” and wide selection of performance parts for the Triumph unit 650, one could pretty much assemble a very competitive race bike. 

Triumph Corporation sent a bulletin to their dealers recommending they contact Trackmaster frames directly, thereby creating an even stronger demand. At the same time, AMA flat track was going through monumental changes. With the introduction of the larger, flat track-specific tire (Goodyear DT), other tire brands followed suit. The new tires offered vastly improved traction due to size, compound, and tread design. Then AMA approved the addition of rear brakes as an option first (1969) and later became mandatory, on all bikes in all classes in 1977. AMA Class C racing was based on racing production models. The rule was 200 models of the homologated bikes were to be in the factory’s warehouse, for AMA inspection and verification. Later, AMA changed the rule from 200 to 25 models for verification. All these new rules played out at Ascot. With all the changes happening, one could see the sport changing almost from week to week. 1969 was the transition year when most of the top riders went to the 750s but a few 500s were still competitive at Ascot. 

By 1971, top riders were on Triumph, BSA twins, many were Trackmaster. Most were Triumph 650s with homologated 750 drop-on top-end kits. Later BSA homologated a 750 kit. In the early 1970s, Linn Kastan started Redline Racing frames and then Doug Schwerma started Champion. Yamaha USA actually sold Champion frame kits and offered engines through their parts department, sold to dealers. Many more custom and flat track frame companies were started during this time. Some people believe AMA racing was “influenced” by Harley, but during that period, most changes benefitted the British brands, primarily Triumph/BSA. Harley had to quickly develop a competitive 750cc OHV 750 (the first XR750 was introduced in 1970). Prior to 1968, Harley had the flathead KR750 race-specific model that generally dominated AMA flat track for over 20 years.

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The new XR750 in its first years was successful with factory riders winning AMA flat track Nationals. Considering it was a first-year racing model, it performed well winning 10 AMA Nationals. Then in 1972, Harley updated the XR750 and introduced the alloy XR750. By 1973, with some notable exceptions, the XR750 dominated Ascot weekly half-mile races. However, the new rule allowed other brands to be very competitive at weekly Ascot half-mile such as Norton, and later Yamaha. Then Honda burst onto the scene with its RS750 V Twins in the 1980s. It later dominated with riders Ricky Graham and Bubba Shobert. Ascot became the epicenter of flat track racing in the US, through the 1960s through the 1970s. Winning a race at Ascot, even a weekly non-national race was heavily publicized by the factories. Privateer riders and teams benefited from support from the factory privateer race support programs, and after-market companies as well. Much of the motorcycle industry’s North American headquarters were based in southern California; Triumph, BSA, Norton, Honda, Yamaha, Suzuki, and Kawasaki, so it was common to see motorcycle industry corporate VIPs watching the races at Ascot. Eventually, most all major brands sponsored factory teams to race at Ascot and on the national circuit. Bell, Bates, and WEBCO plus, other top after-market company’s offices were located in southern California. And they too were drawn into the Ascot action, and some provided contingency at the nationals and even weekly Ascot races. 

During the 1970s, the motorcycle market was rapidly growing and expanding exponentially. The factories wanted race wins to promote their respective brands. It’s where the “Win on Sunday, sell on Monday” sales philosophy was believed by the companies. Riders who would get $50 for a win at a Pro flat track race previously, saw the newer riders getting a salary, race bikes, travel expenses to the races, and full-time mechanic-all paid for by the factories. Many of them were able to keep 100% of their winnings Additionally, the motorcycle market growth benefitted from the epic Bruce Brown film On Any Sunday. The movie positioned motorcycling and motorcycle racing in a positive light creating strong retail demand. There was massive growth in all aspects of the motorcycle market, racing included. At that time, AMA Pro flat track was the number one form of motorcycle racing in the U.S. and if you were a racer, Ascot was the place to race.

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