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.

  1. 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.
    • 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.

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  2. Using a 5/32 Hex or Allen screwdriver, unscrew the two screws from 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.

    How do I get these off if they're real tight? I've already broken a few Allan keys trying and almost striped one of them

    Cameron lambert - Reply

    I have same problem cannot move the inspection cover bolts -

    Skull - Reply

    Use an impact screwdriver.

    Peter - Reply

    • 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.

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    • 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.

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

    With this cover off, do I check anything or is this just to make sure all the oil has drained?

    Don - Reply

    • 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.

    What should I look for while it's open?

    Marty Glynn - Reply

    Not to mention that's where you check ur oil level for the trans but also ur clutch adjustment is be hind that cover. ( type in clutch adjustment for more info)

    Up N coming screwdriver - Reply

    • 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).

    Why not just fill through the top of the oil tank????

    D penglase - Reply

    That's not the same. The oil bag is the crankcase oil and this is showing

    The trans oil. The oil is the same(20w50) but it's two different compartments.

    Up N coming screwdriver - Reply

    • 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.

    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

    Thanks very useful info for beginners

    henryaburchett58 -

    • 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.

    What is the purpose of the inspection hole? Doesn't show oil level

    Doug - Reply

    • 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.

    The 1991 Sportster has the small derby cover like the chain inspection cover and I am sure being a trans / primary I had to by two qts of sport trans and it's the 1st year of the 5 speed trans and belt drive on the xlh1200

    Tcorson - Reply

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Brett Hartt

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but you CANT use gear oil for cluthc!!!

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

Maicol - Reply

Is synthetic 20w50 ok to use?

Jordan -

I change my my transmission oil exactly how it showed and yes the spring with the nut on the end came off and I put it right back. Now I have no tension at all in my clutch basically I have no clutch anymore. This is the first time I've taken the inspection plate off during a transmission fluid change. I usually drain it and automatically just put one quart in. What could I have done wrong?

Argyle - Reply

Did you ever figure out what happened?

Jordan -

Author neglected to say the first numbers on the torque specs are metric (Nm) not ft-lbs as written

Dfh - Reply

Why is the primary chain inspection cover removed?

robin - Reply

Derby cover is removed to insure the primary isn't overfilled.

Chris Moders -

is there not a screw that will drip when filled?

paulposey1997 - Reply

Is Formula + okay to use in primary that shares stator coils? Does it have sulfur additives that can degrade red metals like copper in the stator?

Greg - Reply

does motorcycle stand in vertical position or on its leg stand during oil level inspection ???

irakli ratiani - Reply

Perfectly level in vertical position!Not leaning on jiffy stand.Have someone help you hold it perfectly level.

curtis mozack -

also youre not supposed to use the full quart it WILL puke out.

general rule is 28-29oz

donald ruddell - Reply

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