I have a 1999 fatboy what oil do I use in engine, trans & primary?

There are three, engine oil, transmission oil and primary oil, all are 5/8 inch hex plugs and use o-rings to seal.

Which of the three drain plugs. Primary is on primary case below derby cover; transmission is on right side middle bottom of transmission, engine is at bottom of right rear frame down tube intermediately forward of rear tire. ALL are 5/8 inch hex plugs with 1/4 inch Allen socket in the middle of the plug.

The engine take three quarts, the primary takes 38-44 ounces, and the transmission holds 20-24 ounces. Check the oil in the engine oil tank with the bike on the side stand. As long as the oil is between the lines, do not add oil. When you change the oil and filter, start the engine for 15 seconds and then check the oil. On the primary, stand the bike straight up. Remove the derby cover and fill the primary until the oil comes just up to the bottom of the outer clutch shell. Do not overfill. If you do, the clutch will drag and you will not be able to find neutral with the engine running. Check the transmission with the bike straight up as well. There is a dip stick on the plug where you add the oil. Make sure the oil level is between the lines.

Good Luck
Steve Bentley

Three quarts of engine oil and one quart of primary oil.

Yes, your '99 Fatboy, has the last of the Evo engines in it. They didn't come out with the Twin Cam 88 B engine until 2000. Still, you have three oil compartments, the engine, the primary, and the transmission.

And yes, you can run the H-D Syn3 oil in all three compartments. The engine holds three quarts, the primary holds about a quart (fill to the bottom of the outer clutch drum), and the transmission uses 20-24 ounces.

I hope this answers your questions.

It's trans fluid. It came out of the vent tube just above the primary cover on the top cover of the trans. If you look at the tube, the inside will be wet. Run the bike up to operating temp. Check upright and level.

I’m happy to assist further over the phone at https://www.6ya.com/expert/robert_5bac37c3cb991fdb

You have THREE oil 'compartments' on your particular year&model bike.

(1) The ENGINE OIL
---( which holds 3 to 3.5 quarts or liters of oil).
---On the right side of the bike, and at the rear of the ENGINE OIL TANK, you should notice a Hose that is connected to the oil tank. Follow that Hose downward.
The other end of that hose will either :

----A: Be connected to the bottom of the frame,
OR
----B: Have a Metal Plug in the end of the hose. That 'plug' will be held in the hose via a hose clamp, and also will be secured to the frame via a 'clip' that is actually part of the frame).

-- IF(A): the Hose leads from the tank and is attached to the frame, you will notice a hex-head plug (that also has a hex-cutout in it's center for insertion of a hex or allen key) underneath the part of the frame that the hose is attached to. Remove/Unscrew that Hexplug from the frame to drain the engine oil.

--IF(B): the hose that leads from the Oil Tank has a "HosePlug" that is inserted into the end of the hose, remove that plug to drain the engine oil.

*Removal of the Enging Oil DIPSTICK, located at the mouth/fill area at the top of the Tank will aid in a faster flow of oil from the tank. When done draining, re-install the drain plug.

-When changing the engine oil, also remove and install a new Oil Filter.

*Put in no more than 3 quarts/liters of oil into the Engine Oil Tank.
*Ride your bike for min. of 10 minuets, then park and shut down the engine, wait for about 2 minuets, and check the level via the Dipstick. Proper oil level will be at or just below the 'FULL' mark of the dipstick.

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(2) The TRANSMISSION OIL:

On the right side of the motorcycle, the
TRANSMISSION OIL FILLER PLUG/DIPSTICK is located on the foward facing side of the Transmission End Cover. The Trans End Cover is the cover that the Clutch Cable goes into. The Trans Fill/Dipstick has a Hex/Allen cutout in it for insertion of a hex/allen key to remove it.

The Trans DRAIN PLUG is either located either:
A: -Located on the Transmission Case, JUST BELOW the Trans End Cover. If here, the "Drain Plug" will be a TORX fastener. Remove that Torx fastener to drain the Trans Oil.
OR
B: -Located UNDERNEATH the Trans Case, in between the two Shock Absorbers. If here, the 'Drain Plug" will be a HexPlug that is the same type drain plug as described earlier for the engine drain.

TRANSMISSION OIL QUANTITY is as follows:
** 600 ml. for a 5-speed transmission.
OR
** One Full Quart/Liter for a 6-speed Transmission.

******Use the Trans Dipstick to verify that the level is correct. Between the FULL and ADD mark, or at the FULL mark.

ALSO NOTE: Drain, and Check your Oil when the bike is level. Have a friend assist you if needed. You don't want the bike falling, and/or landing on you.

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(3) The PRIMARY OIL

Located on the LEFT SIDE of motorcycle, the PRIMARY HOUSING connects the Engine Crankshaft TO the Transmission Output Shaft via a Primary Chain, which is lubricated by an oil bath.

(Make sure the Engine Run/Stop Switch is in the STOP or OFF position).

Remove the DERBY COVER (the Large round cover, with 5 Torx Fasteners. With the bike level, you should note that the oil level come to approx. just past the bottom of the Clutch Basket.

The Primary DRAIN PLUG is located: either at the

(A) Left Face of the Outer Primary Cover, below the Derby Cover.
If so, it will be a TORX or HEX/ALLEN fastener. It is NOT the same as the Hex/Allen fasteners that surround the Outer Primary Cover securing it to the Inner Primary Cover.

OR

(B) Located UNDERNEATH and ON the Outer Primary Cover, just below the Derby Cover area. It will either be a HEX FASTENER, or a Torx Fastener.

-Remove the Drain Plug to drain the Primary Oil.
-Reinstall the drain plug and fill (thru the Derby Cover Area) with ONE QUART/LITER of PRIMARY OIL.


****** BE SURE to clean and coat the threads of each Drain Plug with Teflon Paste thread sealant. NOT THREAD LOCKER.

****** BE SURE NOT TO OVER TIGHTEN THE DRAIN PLUGS.

If you are unclear of anything I wrote, please dont' hesitate to get in touch with me through here.
Good Luck , and THANK YOU.
-Marko

Harley's do run hot, anywhere from 220 to 240 normally, and a little hotter this time of year. I suggest running a straight weight oil, and a little heavier weight in the summer. I use Valvoline VR-1 30 weight most of the year, and 50 or 60 weight in the hot summer, and I use Lucas 20w50 primary/trans for the primary and tranny. I don't bother with the extremely high prices of the HD oils. For the whining noise, you need to determine which side of the engine it's coming from. Whining will almost always be in the bottom end. There's nothing in the top end that should whine, and if there is whining from the top, it's usually an air leak around the carb. Start by checking the fluid levels in the tranny, and primary. These are the two most common areas to pick up a whining noise. If it's coming from the left, it's going to be in the primary, and usually this is caused by low fluid levels. From the right, it's going to be either the tranny, low fluid, or the oil pump. The oil pump is a gear type system. If you're running a light weight oil, say a 10w40 or HD 20w50, when the engine heats up and the oil thins, it can cause the oil pump gears to whine a bit, especially in the summer heat. So, check the fluid levels, if they check good, then change the oil, since the summer is coming to an end, go with a straight 30 weight. This should clear up the whining noise. If it doesn't, get back to me with the exact location the noise is coming from, and we'll go to the next level of diagnosing the whine, but I believe that this will cure it.

the trans. and primary are seperate.