Transmission/Primary Oil Change

Changing the transmission oil.

This guide will show you how to change the oil in the transmission of the Evolution motor of the Harley-Davidson Sportster.

The Evolution Sportsters have wet clutch and primary drives. It is recommended to change the oil at 1,000 miles, then every 10,000 miles after that.

The manufacturer recommends using 20w50 oil. Make sure that the oil you use is approved for wet clutches. Many automotive oils are not, so we recommend purchasing an oil that specifically states it's formulated for use in motorcycle transmissions. 75w90 gear oil is often substituted for 20w50 motor oil in this application.

Relevant Parts
  • SAE 20w50 V-Twin Oil Oil must be wet clutch approved. Some automotive oils are not compatible with wet clutches. 75/90 gear oil can also be used. Buy it

Edit Step 1 Workplace Preparation  ¶ 

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Edit Step 1 Workplace Preparation  ¶ 

  • For the best access to the transmission drain plug, optimal draining, and accurate re-filling, we recommend working with the bike secured in an upright position.

Edit Step 2 Removing the Primary Chain Inspection Cover  ¶ 

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Edit Step 2 Removing the Primary Chain Inspection Cover  ¶ 

  • Using a 5/32 Hex or Allen screwdriver, unscrew the two screws from the primary chain inspection cover.

    • Your inspection cover may not be round, depending on the year. However, it will be in the same location and secured by similar screws.

  • Remove the primary chain inspection cover from the transmission housing.

Edit Step 3 Draining the Transmission Oil  ¶ 

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Edit Step 3 Draining the Transmission Oil  ¶ 

  • The transmission drain plug is located on the underside of the transmission on the left side of the bike, near the kickstand bumper.

  • Place a drain pan underneath the drain plug.

  • Using a wrench, unscrew the transmission drain plug and remove it.

    • Your drain plug may be 5/8" or 3/4" depending on the year.

  • Allow all the oil to drain out of the transmission. It should take about five minutes.

Edit Step 4  ¶ 

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Edit Step 4  ¶ 

  • While the oil is draining from the transmission, clean the transmission drain plug.

  • Using a spare rag or paper towel, clean the drain plug, removing excess oil and metal shavings.

    • There is a magnet on the end of the drain plug to capture any ferrous metal residue.

Edit Step 5 Removing the the Clutch Inspection Cover  ¶ 

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Edit Step 5 Removing the the Clutch Inspection Cover  ¶ 

  • Using a T27 screwdriver bit, remove the four screws holding the clutch inspection cover in place.

Edit Step 6  ¶ 

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Edit Step 6  ¶ 

  • Insert a heavy duty spudger or similar prying tool into the gap between the clutch inspection cover and the transmission housing near where clutch cable enters the housing.

  • Gently pry the clutch inspection cover away from the transmission housing.

  • The clutch cover spring may fall out. Be sure to keep track of this and re-install it before replacing the clutch inspection cover.

Edit Step 7 Installing the Transmission Drain Plug  ¶ 

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Edit Step 7 Installing the Transmission Drain Plug  ¶ 

  • Re-insert the transmission drain plug into the transmission housing and hand tighten.

  • Using a 3/4" wrench, tighten down the transmission drain plug.

    • It is important to not over-tighten the drain plug. Tightening the plug too much can strip the threads on the aluminum housing. The plug should be tight, but not too tight. The correct torque specification is 14 - 21 ft-lbs (168 - 252 in-lbs).

Edit Step 8 Adding New Oil  ¶ 

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Edit Step 8 Adding New Oil  ¶ 

  • Insert the nozzle of a funnel into the primary chain inspection hole.

  • Pouring slowly, pour approximately 1 qt of oil into the transmission.

  • As you pour, watch the clutch inspection hole. Make sure that the oil level stays below the edge of the clutch inspection hole.

    • This may require less than the entire quart of oil.

Edit Step 9 Re-assembly  ¶ 

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Edit Step 9 Re-assembly  ¶ 

  • Before re-installing the primary chain inspection cover, make sure the rubber O-ring on the inside of the primary chain inspection hole is clean and properly seated.

  • Also make sure that the rubber o-rings are clean and in proper condition before replacing the screws in the primary chain inspection cover.

  • Using a 5/32" Hex or Allen screw head, re-install the primary chain inspection cover.

Edit Step 10  ¶ 

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Edit Step 10  ¶ 

  • Using a T27 Screwdriver head, reinstall the clutch inspection cover. Install the screws in the following order:

    • Top

    • Bottom

    • Left

    • Right

  • Once all of the screws have been lightly hand-tightened, use a torque wrench to tighten them to their proper specification of 7 - 12 ft-lbs (84 - 108 in-lbs). Tighten the screws in the same order as before.

Required Tools

Heavy-Duty Spudger

$4.95 · 50+ In stock

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Comments Comments are onturn off

but you CANT use gear oil for cluthc!!!

car motor oil CANT be used for bike cluthc!!! Motorcycle motoroil CAN!

Maicol, · Reply

what kind of oil

tabfive99, · Reply

You need to use a motorcycle gear oil.. DO NOT put regular motorcycle motor oil in the transmission. Which is what I almost did after reading this because up top it says 20/50 motor oil. I went to motorcycle shop and asked what kind of transmission oil to use. He said that some people say u r supposed to b able to use the motor oil, but NOT to, as it is bad for the bike. Use gear oil meant for motorcycle transmissions

JWag, · Reply

They say not to use 20w-50 for transmission.

They recommend 75w-90. Gear oil.

Make sure its says GEAR OIL.

Thats what I run on mine.

Alex Flotte, · Reply

SAE 20w50 Motorcycle oil is what is recommended by Harley Davidson. Engine and gear oil are measured on different scales. SAE 20w50 is the same as 75w90 gear oil. Some modern synthetic automotive oils are not compatible with wet clutches. 20w50 is still the correct oil recommended by the manufacturer, just make sure not to buy an oil not approved for use with motorcycle clutches.

Eric Essen, · Reply

Amsoil 20w 50 is specifically for Harley motor oil and wet clutch, it is also the best.

Dirk, · Reply

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