Evo Timeline

1986

  • First year of the Evo Sportster, available in 883 and 1100cc displacement
  • Aluminum heads and cylinders
  • Hydraulic lifters
  • 34mm fixed-venturi Keihin carb
  • 883 heads chamber was a bathtub shape, providing squish bands on both sides. The 883 chamber is also shallower than the 1100/1200 chamber and the valves are longer to match.
  • 883 heads had a 49.5cc chamber, 1.585" diameter intake valves, 1.350" diameter exhaust valves
  • 1100 heads ultra-rare Sportster heads and they were the best factory head ever made for a Sportster until the Thunderstorm head came out in 1998. They have very large valves and a pear-shaped chamber with flat squish bands on each side.
  • 1100 heads 62cc chamber, 1.844" diameter intake valves, 1.610" diameter exhaust valves

1987

  • 883 head changed the chamber shape. It became the 3" round
  • 883 head had 49.5cc chamber, 1.585" diameter intake valves, 1.350" diameter exhaust valves
  • 1100 heads were given smaller valves. The chamber remained largely the same however. These heads are better than the 88-03 1200 heads just due to the better chamber.
  • 1100 heads had 62cc chamber, 1.715" diameter intake valves, 1.480" diameter exhaust valves

Mid-1987

  • 39mm Fork Tubes replaced the older 35mm unit
  • Rear brake caliper updated

1988

  • First year for the 1200 (replacing the 1100)
  • 40mm constant velocity (CV) Keihin slide carb
  • 1200 head chamber was enlarged and the squish bands eliminated to match the new 3.498" bore size and keep the compression ratio down. This results in an open, hemispherical chamber, with poor chamber turbulence
  • 1200 heads had 67cc chamber, 1.715" diameter intake valves, 1.480" diameter exhaust valves

1989

  • Kickstand repositioned farther rearward

1990

  • 40mm (CV) Keihin carb - constant velocity w/accelerator pump

1991

  • 5 speed transmission replaced the 4 speed
  • hydraulic lifters were replaced with automotive type units
  • oil pump given internal cast feed lines
  • breather system moved from the crankcase to the heads (umbrella valves)
  • alternator moved from behind clutch to the crankshaft
  • primary cover redesigned
  • right side timing hole
  • tappet blocks, rear motor mount, oil filter integrated with case
  • one piece push rod tubes
  • cams were relocated to sit directly under the lifters (4 speeds had them slightly offset) and the holes in the head where the pushrods pass through were moved to match
  • crankcase breather was moved from the cam box cover to the bolts in the heads that had previously just held on the carb and air cleaner.

1992

  • standardized hand controls

Mid-1992

  • belt drive replaced chain on 883 deluxe and 1200 models

    1994

    • Oil tank revised (visually identified by relocated oil drain line which now runs to the frame instead of nipple on underside of battery tray)
    • Primary cover changed to have removable derby cover
    • Quick-release clutch cable
    • New electrical system (wiring harness/weatherproof electrical connectors, new electrical component tray under the seat)
    • 883’s got an aluminum lower triple clamp which was previously stock on only the 1200’s
    • Frame changed to straight rear fender struts, had curved fender struts on earlier models

    1995

    • Vacuum operated petcock added to Sportster line
    • Ignition switch moved to steering column (because of petcock)
    • Switched to electric speedo
    • 883’s and 1200’s got the same crank assembly balanced somewhere between the 883 and 1200 piston weights. Prior to this 883’s and 1200’s had separate crank assemblies that were balanced for their specific piston weight.

    1996 - 1997 no changes

    1998

    • Revised ignition system (single fire) on 1200S
    • 1200S gets dual-plug heads (along with hotter cams)

    1999

    • Redesigned shifter detent plate to reduce the effort in shifting and improve accuracy

    2000

    • First year for sealed wheel bearings
    • First year for 4-piston calipers
    • Pressed together flywheel assembly (intended to be stronger and hold it's trueness better)
    • New, finer pitch on the pinion gear and the matching drive gear on the #2 cam
    • Upgraded sprocket rotor in the primary case to reduce problems with the bolts separating from the pulley.  The newer assembly uses 8 bolts rather than the original 4 bolt assembly

    2001

    • New primary chain tensioner with a much thicker steel plate backing up the tensioner shoe
    • All the cam gears were changed to finer pitch setup

    2002

    • New, improved charging rotor/sprocket assembly, part number 32413-92A, held together with 8 bolts (1991-2001 models the alternator hat was held to the front primary sprocket with 4 bolts, and at higher power levels, these like to shear off)

    2003

    • 100th Anniversary Edition - emblems on most models
    • Final year for solid mount models

    2004

    • Engine is rubber mounted
    • Trap door transmission eliminated (cases must now be split to access transmission)
    • Oil tank is mounted further under the seat
    • Rear tire width increased to 150 mm
    • New air cleaner cover
    • Brake calipers, master cylinder, switch housings and handgrips replaced, now exclusive to Sportster models.
    • Heads got new 7mm valve stems and a beehive spring pack just like the XB heads. The new seal assembly affords more retainer to guide seal clearance and can safely accommodate up to .550 lift cams, as compared to .500 in the earlier heads
    • Fins on rubber mount heads are larger than the fins on the earlier heads which improved cooling
    • Front head motor mount bolt holes increased to 7/16-14 (like the Buell head), and the right front bolt hole (pushrod side) has been moved inboard 1/4"
    • Heads are .020" shorter than the previous generation heads, at 3.670" instead of 3.690"
    • 883 received lighter clutch spring than 1200
    • Introduced oil squirters under the pistons to cool the underside of the piston domes

    2005

    • Swing arm & rear wheel re-designed to accommodate 1" rear axle

    2006  no changes

    2007

    • Primary cover & shifter shaft changes
    • Bolt pattern widened for the intake manifold flanges
    • Small change to the floor of the intake port. The change actually makes the flow through this port slightly less laminar than the 2004-2006 head. It's not an enormous difference, but in stock form this head is capable of supporting a few horsepower less
    • The surface where the manifold attaches was changed to accommodate the EFI throttle body. This area was machined down 1/16 of an inch (.0625") as compared to all previous carb type heads