Table of Contents
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EVO: Transmission & Final Drive
1986-1990 4-Speed Constant Mesh Transmission w/Trapdoor
- The rear compartment of the left and right engine case halves form the transmission housing or case. An access cover, or trapdoor, is mounted on the left side of the case (inside) behind the primary cover. The main components of the transmission are mounted to this trapdoor to allow you to detach the one cover (together with all the transmission components) for easy removal and servicing without having to split the engine cases in half which otherwise would be a full engine re-build.
Specifications
Clutch
1986-1990 Wet Clutch Information 1) | ||
---|---|---|
Clutch plate thickness | –Friction (drive) plate (fiber) | 0.0150 in. (± 0.0031 in.) / 3.810 mm (± 0.079 mm) |
–Steel plate (driven) plate | 0.0629 in. (± 0.0020 in.) / 1.598 mm (± 0.51 mm) | |
Minimum Thickness (wear limit) | –Friction (fiber) plate | 0.130 in. min. / (3.302 mm) |
–Steel plate | 0.060 in. min. / (0.0254 mm) | |
Maximum allowable warp-age | –Friction (fiber) plate | 0.0010 in. max. / (0.0254 mm) |
–Steel plate | 0.0010 in. max./ (0.0254 mm) | |
Capacity | 174 ft-lbs | |
Spring Force | Engaged: 304 lbs | Disengaged: 260 lbs |
Clutch shell bearing on clutch gear (loose) | 0.0000 in-0.0010 in. / (0.0254 mm) |
Primary Drive (engine to transmission)
Year | Domestic Model(s) | Engine Sprocket | Clutch Sprocket | Ratio |
---|---|---|---|---|
1986-1990 | All Models2) | 34 Teeth | 59 Teeth | 1.676:1 |
Primary / Transmission Oil Capacities
The MoCo publishes for 1986-1990 3) | 1.5 pints (24 oz), (710 ml) |
* This quantity is for a dry application. When changing oil, use your own judgement not to overfill as you won't need a full 1.5 pints to re-fill the oil.
Transmission
Final Drive (Trans to Wheel)
Final Drive Sprocket Torque (on Chain Drive Models) | |||
---|---|---|---|
Nut Description | Nut Size | Tightening Torque | Notes |
1986-90 | 1-1/8“ Nut - Right-hand Threads | 35-64 ft-lbs | Max 90ft-lbs |
(use only 2 or 3 drops of RED threadlocker on this nut) |
Year | Domestic Model(s) | Transmission Sprocket | Rear Wheel Sprocket | Ratio |
---|---|---|---|---|
1986-1990 | All Models6) | 21 Teeth | 48 Teeth | 2.29:1 |
Fastener Torque Specs
Mainshaft nut locking screw | 50 - 60 in-lbs. |
Mainshaft nut | 35 - 65 ft-lbs. |
Engine sprocket nut | 150 - 165 ft-lbs. |
Drain plug | 14 - 21 ft-lbs. |
Front chaincase / primary cover screws | 80 - 110 in-lbs. |
Access \ Trapdoor cover bolts | 14-19 ft-lbs. |
Stator Torx nuts | 30 - 40 in-lbs. |
Footrest nut | 24-36 ft-lbs. |
Shift lever pinch-bolt | 90 - 110 in-lbs. |
Neutral indicator switch | 3 - 5 ft-lbs. |
Chain tensioner stud nut | 8 - 12 ft lbs |
Clutch release mechanism | 22 - 30 in. lbs |
Mainshaft Group
Countershaft Group
Discussion
1986-90 Evo Sportsters: What every owner should know but were afraid to ask
An __XLForum Thread__ By Four Speed
1)
1986-1990 HD HLX FSM pg 6-1
3)
1986-1990 HD Sportster FSM pg 2-1
4)
Number of clutch gear revolutions to drive mainshaft sprocket one revolution.
5)
Number of engine revolutions to drive rear wheel one revolution.