Harley Ironhead Sportsters
The Ironhead Engine... The Last Real Harley?
As you may have guessed, this motorcycle website is dedicated to the all-time loudest and meanest V twin Harley Davidson engine: the Ironhead.
The Ironhead Sportster engine was introduced in 1957 with the X Model Harley Davidson Sportster and lasted almost 30 years (THIRTY years !!!) until in 1986 this beautiful powerpack was replaced by the current Harley Evolution or Evo engine.
Sportster History (don't worry, we'll keep it short...)
Before Sportsters: The Harley Model K
The history of the Sportster starts with its predecessor, the Model K.
The first Model K was introduced by the Harley Davidson Motor Company in 1952 in response to the invasion of the American motorcycle market by lighter and faster British bikes like BSA, Norton and Triumph. The 1952 Model K featured a conservative 45 cubic inches (750cc) side-valve V-twin engine of pre-war design.
In the 1954 Model KH the K's engine had been upgraded to 54 cubic inches (883cc). The following year, Harley introduced the high performance Model KHK which featured a speed kit: roller-bearing bottom end, hot cams and polished ports.
1957: The Harley Sportster XL Series
In 1957 Harley Davidson introduced the XL Series "Sportster" motorcycle which looked very similar to the Model K Series except that the 54 cubic inches (883cc) side-valve V-twin engine with its aluminium heads and cylinders was replaced by the 54 cubic inches (883cc) overhead valve (OHV) engine which featured iron heads and cylinders. Otherwise, the 1957 Sportster XL had the same basic frame, engine case, right foot shift, right side drive chain, telescopic front fork, rear suspension and brake drums as the 1956 Model K.
In 1958 Harley introduced the Sportster XLCH. Many sources say the "CH" stands for "Competition Hot" while others say the H stands for "High pressure". In any case, the XLCH is a stripped-down lighter and faster version of the XL, with a staggered dual exhaust and peanut gas tank.
The Sportster XLH was the heavier touring version of the Sportster XLCH.
1972: Frame Modifications and 1000cc
In 1972 the Sportster Ironhead 55 cubic inch (883cc) overhead-valve engine was beefed up to 61 cubic inch or 1000cc.
Harley Davidson modified the Sportster frame whereby the cast steel connection node at the top rear of the frame (i.e. underneath the saddle) was replaced by a U shaped stamped and welded connection made of steel strip. While officially this frame design change took place in the year 1972, worldwide delivery of Sportsters with the old frame lasted until well into 1973.
The stamped and welded U shaped connection underneath the saddle of the Sporty was not a big success. A few months after its introduction, the stamped and welded U shaped connection appeared to be not strong enough to withstand the dynamic and cyclic vertical loading introduced during riding by the rear shocks and heavy rear fender.
This forced the Motor Company to recall all newly delivered Sportsters back to the dealers who were provided with steel reinforcement strips that had to be welded in place diagonally to strengthen the support points of the rear shock absorber and rear fender strut.
1974: Right Foot Shift Moves to the Left
When the Sportster Ironhead engine was introduced in 1957, she inherited the whole lower end - including right foot shift - from her direct predecessor Harley Davidson Flathead KH, KHK and XR motorcycle models. These Flatheads had their roots deep into flat track racing, that's why they had the right foot shift.
In the early 1970's, the US DOT mandated left side shift for all new motorcycles, probably for reasons of safety. In 1974 the Motor Company switched from right to left, although you shouldn't be surprised to see a 1974 Sportster with right foot shift. That's probably a 1973 model delivered and registered in 1974.
From 1974 until 1977 Harley Davidson applied a rather crude solution to switch the shifting from the right to left by simply running a secondary shaft underneath the frame, which was connected to an extremely long shift lever as shown on the photograph. Only in the year 1977 Harley redesigned the transmission box to allow the gear shift shaft to exit to the left.
Chris from DownUnder:
"The last year of the right hand shift was 1974. 1975 and 1976 was the years where the linkage was used, and 1977 was the 1st year of the through the crankcase left hand shift.
I recall more than one writer in the mainstream press during the mid 70's predicting that the left hand shift requirement would spell doom for the traditional Sporty, ha!!! 1977 was also the last year of the single front disc.
I remember as a young twenty something lusting after a 1974 Sportster brand new on the Dealers floor, especially the lean kickstart model with that supercool but impossibly uncomfortable seat.
The 1977 was possibly a better built model as Harley struggled to rectify the catastrophic quality control of the 1971 to 1973 years, and also didn't have the problem of the unsplined gearshift lever shaft.
More that one person used to curse at their early 70's Sportsters when the gearshift lever would slowly work its way around the gearshift shaft, eventually developing stress cracks from overtightening ..."
1979: The Sportster Frame Modified Once More
So, around 1979 another change to the Sporty frame design took place whereby the stamped and welded connection underneath the saddle was replaced by an inverted triangle constructed from steel tubing, like seen on many British and Japanese bikes. In 1982 this triangular frame design was revised to improve the construction of the rear shock support point.
1986: End of the Ironhead - The Last Real Harley?
In 1986, Harley Davidson replaced the 1000cc Ironhead engine with the 1100cc Sportster Evolution or Evo engine. Because the smoother running Evo engine was developed with considerable help from outside the Motor Company, many people maintain that the Ironhead engine was the last real Harley engine...