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About Ironheads

The Gimp's Ironhead Sportster About the Ironhead Sportster Rebuilding the Ironhead Sportster My Files

1957-1984

The Ironheads were developed from the K model in 1957. This was in the heyday of Flat-Track racing. At 900CC, the 57 Sportster was the "King of the Hill" which kept most records against the British bikes by Ariel, Norton, BSA, and Triumph. The only bike which was more powerfull was the Vincent Black Shadow. The Ironhead Sportster is a 45degree V-twin with Hemisphereical combustion chambers and High Dome pistons. This design was practical until the decrease in the octane rating of gasoline. The configuration is prone to Ping or Detonation of the fuel/air mixture causing performance problems with todays unleaded gasoline. The problem can be minimized by proper tuning, or eliminated by conversion to dual spark plugs.

The Ironhead preceeded the EVO Sportster which was introduced in 1985. The Sportster is the longest running production model of any motorcycle.

The bike I have is a 1975 XLCH. It was produced when AMF (The sports mega company) owned HD. There were approximately 5300 Sportsters produced in 1975.

The engine displacement is 61C.I.D. (1000cc). This had been upgraded in 1968 from 54C.I.D. 900cc. The Sportster displacement marking on the left side Primary Cover is in cc instead of the tradiditonal C.I.D.

Harley Davidson continues to make the Sportster with the traditonal overhead valve side cam configuration. There are four cams in the Sportster.

Brief History

Harley Davidson made "Flat Head" (WL) engines with the valves on the side of the cylinder as their entier product line up until the introduction of the "Knuckle head" (Model EL, 61 C.I.D.) in 1936 (through 1947). Post WWII years saw the Overhaead valve EL prove to be a highly reliable and high performance engine. The EL was followed by the FL "Pan Head" (1947-1965). The FL was introduced as a 74C.I.D engine, which was also available in th 80C.I.D. version.
However, they continued making the smaller WL 45C.I.D flat head up through the mid 70s. It was primairly used in Service Cars (Trikes) used by police for parking ticket servicing, along with Ice Cream Vendors.
The racing market was addressed by the WL/WLA until the introduction of the KH model in 1954-55. The KH was different in that it was of the integral Transmission/engine type. All Harley Davidsons in the past had a seperate engine and transmission. The KH was upgraded with overhead valves and introduced in 1957 as the XL.
As with many models from Harley Davidson, the XL has been offered in several variants over the years.
The first variant was the H model, or XLH. The H designated a more powerful engine due to changes in the cams and compression. This was followed by the C model XLC which was a special version for california. Next was the XLCH which was a kick only (no electric Start) high performance version. The last version was the XLCR Cafe Racer.

Harleydavidson also made true racing bikes including the 750cc XR for TT racing.  

The 750cc XR was also used by Evil Knievel for many of his stunts.

ROLLING CHASSIS

When I bought my Sportster, it was what is considered a "Rolling Chassis". This describes a bike which is partially dissasembled but should be complete.

Since I knew the person I was buying it from, I was certain it was complete. However, whenever you buy a used bike, it is a pig in a poke so to speak. It only ran for about 500 miles once I got it back together before one of the rod bearings went out.
So, with a bad rod bearing, there was not much choice in what to do. The engine had to have the bottom end rebuilt, and I figured I might as well have it rebored and put new pistons and rings in it. That would take a while, so I might as well restore the whole bike.

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