A Fluid Change for the Road King

The last couple of days the weather has been touch and go, but the rain has been pretty consistent today since early this morning so I decided to put the Road King up on the lift and change the fluids before I gave her a bath and a wax to jump into spring.


I went through the trike earlier this year and have recently spent a lot of time getting the Sporty ready to ride, so I decided it was time to spend some quality time with the Road King. If I can't be riding on a Saturday, working on the bikes is a great way to spend a Saturday morning.


Every time I do a project with one of the bikes, I realize how much I appreciate my motorcycle lift. I don't know how I went for so many years without one. It makes little jobs like this so much easier. 

Once the bike was up, I slide my oil pan underneath to start the process.


I start by removing the dipstick to check the current oil level. Then I set the dipstick aside—it reminds me that I'm either draining the oil or the oil tank is empty.

I try to implement some standard shop practices like that to make sure I don't forget anything. Most of them have evolved over the years as I've done something dumb or otherwise forgotten something. I like the familiar routine.


Sue's bike, a 98' Evo, my 04' Twin Cam, and Kelly's 12' Twin Cam have all been on the lift for this and the oil drain plug is on the left side facing forward on all of them. And, they all take a 5/8 socket or wrench to loosen the plug.


Make sure the pan you're going to use to catch the oil is at the ready, because once you pull the plug, the oil starts draining pretty quickly and it won't take long before you have a good size mess under the bike.

There is a magnet on the end of the drain plug that will help you determine if there's anything in there that would indicate a problem—like metal shavings. So inspect the magnet once you have the plug removed.


I know a few guys who inspect the o-ring before they replace it, and if it looks bad, they make a change. Because they are so cheap (the o-rings not my friends), I prefer to just change out the o-ring every time I change the fluids.

I used to just buy a handful of o-rings when I went into the dealership from Harley, but I have since purchased a handy-dandy selection of o-rings so I always have what I need ready. 


I've mentioned before that I really like Red Line synthetic motor oil. I started using it several years ago and, although it costs a little more, I feel confident in the way it keeps the engine lubricated.

With almost 100,000 miles on this bike, and no major mechanical issues whatsoever, I think it's a good testament to the job it does inside this Twin Cam. That and the fact that I'm pretty religious about regular fluid changes. 

What's more, she doesn't leak a drop. I can't say the same thing for Sue's EVO.


I'm also a fan of the K&N oil filter and have them on all the bikes. Because they all take different filters, and I like to have at least one of two on the shelf at any given time, I label them when they come in so I don't have to remember part numbers.

I've tried several different ways of removing the old filter (this is probably the messiest part of a fluid change), and I think I like the large plastic bag method the best. I've got one of the funnels that slides under the filter so you can catch the oil in your  drain pan, and tend to go back and forth between the funnel and the plastic bag, but today I'm favoring the plastic bag.

Basically, you slide the plastic bag under the filter to catch any oil that's left inside and remove the filter with the plastic bag over it. There will still be some oil get by you, but it catches most of it.

The nut on the end of the filter makes it a lot easier to take off with the plastic bag method too.


Before I install the new filter, I put some oil in it and rub a little oil around the rubber seal before I screw it on. I was also taught that the filter only needs to be hand tight, so I screw it on by hand as tight as I can get it and don't use a wrench to install it.


I use a funnel to fill the oil, but it's not a requirement. I guess it would depend upon how tidy you were. Me, I make a big enough mess as it is, so I use every means at my disposal to keep the oil in the motorcycle rather than all over the garage. With that being said, you can tell by looking at the floor of the garage, that I haven't been very good at it.

The bike takes 3-1/2 quarts, so when I get about halfway done with the fourth quart, I measure. I put a big "X" on the opened container of oil to identify it. It tends to get used to top things off (I mentioned Sue's bike had a little drip) or I use that to fill the oil can.


I do the same thing with the transmission that I do with the oil. I remove the filler cap and set it aside.


The transmission oil drain plug is facing down on the right side of the bike underneath the transmission. It also takes a 5/8" socket or wrench to remove it.

As with the engine oil, you'll want to inspect the magnet on the end of the plug for shavings or anything that would indicate you have an issue inside the transmission.

You'll also want to inspect and replace the o-ring. This time, the o-ring looks pretty mangled, so it's obvious it needs to be replaced. But I always do it anyway. It feels like cheap insurance to me.


This is just one man's opinion, but here it is. The Red Line oil is great, but the transmission oil with Shockproof, is the stuff dreams are made of. This stuff is simply the best transmission fluid I have ever put in my bike. 

When we got Sue's bike, the transmission felt a little clunky, but after a couple of quarts of this stuff had run through the transmission, it's made her feel like a new bike. I have to admit, I've thought it was just me (confirmation bias), until Sue mentioned that she could feel a difference and asked me what I had done.

What's more, because it's pink, if there's a leak under the bike it's easier to identify where it's coming from.


Next, the primary.

For the last couple of years I have been using Harley's gasket instead of the o-ring. They said it was the replacement for the o-ring and it seems to work fine. This is what it looks like under the derby cover.


The drain plug for the primary fluid is underneath the derby cover.

Pull the plug, inspect and replace the o-ring, and drain the fluid. This is another time you'll want to make sure your drain pan is positioned under the plug or you'll have primary fluid all over the floor.


I have a number of friends, like Kelly, who don't think it really matters what fluid you use in the primary. He tends to fill it with Harley's semi-synthetic. And, he's probably right since all you want to do is keep the clutch plates wet.

Nevertheless, I use Red Line's Primary Case Oil.

I also went a long time without the special funnel. In all honesty, I don't think I ever missed it—until I decided to give it a try. It really does make filling the primary easy. I'm glad I have it.


Before I install the derby cover gasket and then re-install the derby cover, I smear a little bit of oil around the raised ring on the gasket to help encourage a good seal.

All the drain plugs and the derby cover fasteners have a torque spec. There are a lot of guys who don't bother with it, and there are times when I haven't either, but these days I tend to just follow the spec. The correct spec will be in your shop manual and it only takes a few more seconds to use a torque wrench and do it right.

I have a small whiteboard on the wall in the garage where I log the service intervals on the bikes. so I'm always aware of what's been done last and when it was done. That way I don't have to rely on my memory.