Using a standard Super X as the basis for his motor, Constantine changed the ratio between the bore and the stroke and designed hemispherical combustion chambers with oversize valves (the old Excelsior strategy).  The overhead-valves were compressed by double chrome vanadium wire springs, each cylinder exhausting through twin ports.  The new motor (with a compression ratio of 10:1) was designed to run on alcohol-benzol fuel, and when dyno-tested was said to develop one horsepower per cubic inch!

In addition to riding for Excelsior, the mechanically-gifted Petrali did some engineering for his Chicago employer.  In 1928, one of Petrali's projects was a 61 cubic inch hillclimber that he developed by mating the earlier "M" type cylinder to the Super X crankcase;  this was the cylinder that was first developed in 1921 for use by Paul Anderson and Maldwyn Jones on their 1/2-mile dirt track machines.  Petrali's new "Climber" was affectionately called "Big Bertha," and together with Constantine's new overhead-valve 45 presented a formidable challenge for the Springfield and Milwaukee companies.

By 1928, Harley-Davidson could no longer ignore the potent 45 cubic inch motors fielded by their competition.  Two years earlier, Excelsior had demonstrated race-sustaining speeds in excess of 107 mph with their 45 cubic inch Super X, and in 1928 Indian overhead 45's took the lead in National Championship events at speeds in excess of 111 mph.

Harley-Davidson did not have a motor with which to compete in the new 45 cubic inch class of racing.  The company's initial effort was to modify their 21 cubic inch "Peashooter" OHV top end and combine it with their race-proven, 61 cubic inch 2-cam motor.  The result was a hybrid 2-cam overhead-valve 45.  Although the Milwaukee company fielded several examples of this motor in 1928, the H-D "hybrid" was not competitive with the Excelsior and Indian entries.

The Davidson brothers and William Harley watched helplessly as their Springfield rival won every National Championship race contested that year.  Even the greatly diminished Excelsior company was able to advertise significant victories in both flat track and hillclimb events.

With a resurgence in motorcycle sales as an incentive, H-D authorized the design of an entirely new 45 cubic inch race motor with the hope of regaining their formerly dominant position in American racing.  Harley's new motor, an overhead 45 cataloged as the "DAH," made its debut at a Pittsburgh, Pennsylvania hillclimb in July of 1929.  With two stubby exhaust stacks exiting each cylinder and Schebler barrel-valve alcohol carburetor, the new H-D entry announced Milwaukee's serious intentions.

Indeed, Bill Ottaway's presence at track side, conjured up the vision of year's past when Harley-Davidson, in any given race, was favored to receive the checkered flag at the finish.  Maybe Ottaway's presence brought the Milwaukee company good luck.  John Grove, aboard the new machine, won the Pittsburgh hillclimb's 45 cubic inch expert event, giving H-D their first significant victory of the past two years.

Excelsior and Indian, however, continued to dominate American racing for the 1929 season.  For the 2nd year in a row, the Springfield company won every National Championship track contest, and Excelsior brought home the honors in the popular and important hillclimbs.  Constantine's efforts had been successful, both of Schwinn's entries were victorious in the 1929 Hillclimb Championship. Petrali was the overall National Champion, and his teammate, Gene Rhyne, was the runner-up.

In 1930, the manufacturers went all out. Petrali and Rhyne's victories had provided Schwinn's company with reams of advertising copy, and both Indian and H-D were anxious to claim the Championship and the publicity for themselves.  Once again, the "title event" was held in Muskegon, Michigan, on the 328 foot hill known as Mt.Garfield.  As expected, thousands of spectators thronged to the event in order to see for themselves who would be crowned "king of the hill."  Excelsior brought its winning combination to defend their "crown;"  while the Springfield company brought their "Altoona" overheads along with their star "slant artists," Orrie Steele and Howard Mitzell.

Although Harley-Davidson brought both their 61 cubic inch 2-cam as well as their new 45 overhead, the Milwaukee company was still a year or two behind the competition in the final development of their professional race equipment.  As it turned out, the 1930 hillclimb championship came down to a contest between Indian and Excelsior.  Gene Rhyne, Excelsior's runner-up for the 1929 title, jumped into the lead by winning the 45 cubic inch professional event in 14.06 seconds.  Then Gene made a run in the 61 cubic inch pro class with a time of 14.13 seconds.

As the remaining contestants completed their runs, it began to look like Rhyne had the event won for Schwinn's Chicago company -- then Howard Mitzell came to the line on his factory-prepared Indian overhead.  The following is an account of the action that followed as reported in MotorCycling Magazine:

Mitzell did the trick in time that looks like it's going to be mighty tough for Gene to beat, and it was small wonder that the red men grabbed Howard as he trudged down the hill and bore him around the grounds in triumph.  But the folks didn't measure up Gene's caliber. They didn't realize they were dealing with a newly-crowned champion who just wasn't going to let his laurels be grabbed by anybody else.

The boys brought out Big Bertha and Gene nonchalantly climbed into the saddle.  The trail ahead of him was rougher than a plowed field.  The sun had by this time perched directly on top of Mt. Garfield, shining directly down the course into the riders' eyes.  Leisurely he warms up the motor and prepares to cut loose with more horses than have been unlimbered on the hill at any time during the day.  The crowd realizes that a crisis has arrived and is tense and breathless.  Nobody wants to miss a single glimpse of the ride that will tell whether Gene or Howard will wear the 1930 heavyweight crown.

With a roar, a flash of flame, a wild leap and a shower of stones, sand and sod, Gene is off on his way.  Up and up he shoots in far less time than it takes to write this line.  Without a waver, he steers right through the center of the course.  He has no time to worry about the holes or steps.  On the last ledge his front wheel comes up and he hurtles across the string on his hind wheel.  Eyes and ears cannot split seconds, but they can tell pretty accurately when a ride is fast.

As the last roar echoes away there is absolute silence.  The spectators are anchored spellbound.  Even the timers seem stunned and they study the clocks.  After what seems an age the announcer ambles over to the "mike" and shouts: "Gene Rhyne, over the top in 12.37 seconds."

In reviewing the results for the five championship track events held at the Fall meet in Syracuse, New York, the only recognizable name from the old days was Jim Davis.  The 30 year-old motorcycle racer was still going strong, winning yet another Championship for his Springfield employer.  Significantly, in the article summarizing the year's results, the major motorcycle publication of the day noted the declining number of race tracks caused by real estate developments.