So I know this has been hashed over repeatedly as there are other threads about it. What size tank do I really have 3.8 gal. or 4.2 gal.? Im told by very good mechanics its 3.8 gal. on fxr center fill tanks. You wont get 4 gal. of gas in it. What about the side fill tanks on an fxlr and an fxr2,3 and 4?

 

Mines 4.4. Never got more than 3.8 or so into it.

 

The center fill FXRS is 4.2 gallons. When you turn on the reserve, there are 0.4 gallons left in the tank, which means you have used 3.8 gallons.

 

I know what your saying and thats what Ive always called it too. 4.2 gal. tank. But total of the tank is the total capacity. Reserve is done through the fuel valve or petcock...so its not added to capacity. Reserve is always subtracted, never added. That's why I'm questioning referring to the tank as 4.2 gallons. Its really a 3.8 gal. tank with .4 for reserve. Its all in the way we top off the tank compared to the way the moco advised in the manual maybe?

 

If you empty all of the fuel out of the tank, you will be able to put 4.2 gallons in it. It's total capacity is 4.2 gallons. It is a 4.2 gallon tank. That is what it has always been called, at least since I bought my bike in '85.

 

Ive never run mine dry so I guess i will have to try it and see. I have my doubts that it will hold that much though.

 

FXR center-fill tanks are 3.8 gal. The side-fill tanks on FXLRS and FXR 2/3/4 models are the larger 4.2 gal capacity. You're right, you'll never actually get a full 4 gallons in the 3.8.

 

I have been riding my '85 FXRS with center fill tank since January 1986. 4.2 gallons.

 

Its known through advertising by the moco that they were called 4.2 gal. tanks. Its also in the owners manual as 3.8 gal.total capacity fuel tank, not a 4.2 gal tank. You cant argue that fact. I guess you can call them whatever you like. Kinda like splitting hairs.

 

I call them center fill tanks and leave it there, all the rest is semantics haha The math was already explained above, ~0.4 in reserve + 3.8 = 4.2 total but why Harley bounces between the two we will probably never know. There is plenty of Harley examples of confusing communications to say the least haha You wouldnt care about capacity much anyway, if trying to calculate real MPG you would top it off, ride, top it off again and use that consumption as your metric, if trying to use that to calculate your total "range" in a tank for a long ride, well you better deduct ~10-20 miles to play it safe or you'll have some pist off friends pushing you down the highway

Down south between the CA to AZ stretch, there is a section of highway somewhere out side of Palm Springs where the gas stops are 93 miles apart. One trip I was on my 5 speed 90 FXR with a lil pumped up 80" and I would average about 100 miles to a tank since I liked to ride it like a dirt bike. Well when your cruise speed on the freeway is 85-90 straight your MPG goes down and on that stretch in the middle of the desert in the middle of the night I clicked on the reserve at about 80 miles on the odometer and started to sweat a little bit. Gave my brother next to me the hand signal, he knew that if I waved him while riding to be ready to peg me (that has a whole new meaning nowadays haha) as Im out of gas and cant stop. Luckily I made it to the gas station on fumes, the bike actually died pulling in when I slowed down. Moral of that story, dont be that guy and give your friends with 6 speeds more ammo to talk sh*t about the classics haha