Table of Contents
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EVO: Oiling & Lubrication - Sub-01F
Drain Oil Passages Through Pics
86-90 Engines
Gravity Drains
- Gravity oil (drained from rocker boxes and head/cylinder drainage) falls on moving parts and into the crankcase.
- Oil collected in the rocker box is returned to the crankcase through a passage in the cylinder and the head.
- Oil collected in the push rod areas of the heads / rockers flows down the pushrod covers.
- Then it flows down into the gearcase / cam chest through drain holes through in the tappet blocks.
- Collected oil in the gearcase is routed to the crankshaft sump area via a low hole in the wall between them on the right side of the pinion shaft.
- Excess oil mist drawn into the gearcase breather is separated from crankcase air pressure at the gearcase breather valve.
- The separated oil (and condensed oil in the exit hose) flows into a drain hole below the breather valve and back into the gearcase.
Tappet blocks are directional (rear exhaust shown below).
2) 3)
Splash
- Occasional excess pressured oil (from the oil filter pad) is dumped into the gearcase by the oil pressure relief valve.
- High pressure oil, when cold (on startup), opens the pressure regulator.
- The excess oil is dumped into the gearcase and routed to the sump area via the low hole in the wall between the gearcase and the crankcase.
- Splash oil in the sump area of the crankcase serves to lubricate the moving parts as well.
- Splash oil (from the up and down movement of the connecting rods, crankshaft and pressure generated under the pistons on downstroke) serves to lubricate;
- Cylinder walls
- Pistons, piston pins
- Cam gears and bushings
- Main bearings
86-90 engine sump splash holes 4) |
Oil Pump Scavenge
91-Up Engines
Gravity
- Gravity oil (drained from rocker boxes and head/cylinder drainage) falls on moving parts and into the crankcase.
- (91 only) - Occasional excess pressured oil (from the oil filter pad) is dumped into the gearcase by the oil pressure relief valve.
- 91 engines kept the oil pressure relief valve that opens at 30-35 psi and dumps oil into the gearcase.
- The pressure relief was removed from future models.
- 91-03
- Oil collected in the rocker box is returned to the crankcase through a passage in each head and cylinder.
- Oil collected in the push rod areas of the heads / rockers flows down the pushrod covers.
- Then it flows down into the gearcase / cam chest through vertical drain holes in the tappet blocks.
- Excess oil mist splashed into the rocker boxes is separated from crankcase air pressure at the breather baffles (plain umbrella valves).
- The separated oil flows into drain holes in the rocker boxes and back into the crankcase.
Rocker box drainage 12) |
91-03 breather holes in the rocker box sections and head 13) | ||
- 04-Up
- Oil collected in the rocker box is returned to the gearcase through a passage in the head and the right case.
- Oil collected in the push rod areas of the heads / rockers flows down the pushrod covers.
- Then it flows down into the gearcase / cam chest through vertical drain holes in the tappet blocks.
- Excess oil mist splashed into the rocker boxes is separated from crankcase air pressure at the breather baffles (fancy umbrella valves).
- The separated oil flows into drain holes in the rocker boxes and back into the gearcase.
Head drains in the cylinders 18) 1 hole is plugged on each cylinder during installation. | Head drains at the cylinder base on the case 19) |
Milled slots in the left case match milled slots in the right case for rocker box drain from valve side. 20) | Lower part of slots in the right case exit thru drilled holes into the gearcase. 21) | |
Rocker box drains into the cam chest. 22) | |
21)
photo by meherdad_it of the XLFORUM, labeled by Hippysmack https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/105751-installing-the-90-nrhs?threadid=944843