Table of Contents
This is an old revision of the document!
EVO: Transmission & Final Drive
1986-1990 4-Speed Constant Mesh Wet Clutch Transmission w/Trapdoor
| Click here for tips on 4 Speed Transmission Removal / Inspection / Installation | ||
|---|---|---|
 |  |  |
| 1990 4 Speed Transmission 1) | ||
 |  | |
| 1990 4 Speed Transmission 2) | ||
Specifications
Clutch
| 1986-1990 Wet Clutch Information 3) | ||
|---|---|---|
| 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 Models4) | 34 Teeth | 59 Teeth | 1.676:1 |
Primary / Transmission Oil Capacities
| The MoCo publishes for 1986-1990 5) | 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
- Internal Gear Ratios are the number of clutch gear revolutions to drive the mainshaft sprocket one revolution.
- Overall Gear Ratios are the number of engine revolutions to drive rear wheel one revolution.
| Year (all models) Internal Gear Ratios | ||||
|---|---|---|---|---|
| 1st | 2nd | 3rd | 4th | |
| 1986 | 2.52 | 1.82 | 1.38 | 1.00 |
| 1987-1990 | 2.29 | 1.66 | 1.25 | 1.00 |
| Year (all models) | Overall Gear Ratios | |||
| 1st | 2nd | 3rd | 4th | |
| 1986 | 10.00 | 7.25 | 5.48 | 3.97 |
| 1987-1990 | 9.12 | 6.59 | 4.98 | 3.97 |
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
- Clutch gear ball bearing in access cover: .001 - .00012 in. loose
- Wear limit: .0035 in.
- Ball bearing on clutch gear: .0009 in. max. tight
- Wear limit: .001 in. loose
- Clutch gear needle bearing journal diameter: .7495 - .7500 in.
- Wear limit: .7485 in.
- Mainshaft right side retained roller bearing: .0004 - .0015 in. loose
- Wear limit: .0035 in. loose
- Mainshaft end play:
- Minimum: .006 in. / Maximum .020 in.
- Mainshaft third gear on shaft: .0027 - .0038 in. loose
- Wear limit: .004 loose
- End play: .006 - .020 in.
- Clearance between clutch faces:
- Mainshaft fourth gear and second gear: .040 min. - .080 in. max.
- Mainshaft third gear and second gear: .040 min. - .080 in. max.
Countershaft Group
- Countershaft end bearings: Retained needle roller bearings
- Countershaft needle bearing journal diameter:
- Access door side or end: .7500 - .7495 in.
- Wear limit: .7490 in.
- Right crankcase side or end: .6875 - .6870 in.
- Wear limit: .6865 in.
- Bearing fit in case: Press fit
- Second gear on shaft:.001 - .0025 in. loose
- Low gear needle bearing journal diameter: .6875 - .6870 in.
- Wear limit: .6865 in.
- Clearance between faces:
- Countershaft low and third gear: .040 - .080 in. max.
- Countershaft second gear and third gear: .040 - .080 in. max.
- Countershaft end play: .004 - .015 in. max.
Discussion
1986-90 Evo Sportsters: What every owner should know but were afraid to ask
An __XLForum Thread__ By Four Speed
1)
photos by Dave 76 of the XLFORUM http://xlforum.net/vbportal/forums/showthread.php?t=513989&highlight=speed
2)
photos by Dave 76 of the XLFORUM http://xlforum.net/vbportal/forums/showthread.php?t=513989&highlight=speed
3)
1986-1990 HD HLX FSM pg 6-1
5)
1986-1990 HD Sportster FSM pg 2-1
