Changed the fork oil in my bike tonight. Total time was about an hour. Did you know The Book says to change the fork oil every 5K miles? That's like the same as the primary or transmission oil. I change those religiously every other motor oil change, 2.5K miles on the motor oil, 5K on the primary and trans. Fork oil, not so much. That's historically kinda been "change it with the seals..." Yeah, not exactly every 5K miles. Part of the problem was the shop manual telling me to disassemble the front half of the bike to change the oil. Faring, dash, etc., all come off. OK, so we know you don't have to do that.

So here's what I did this evening: Put bike upright on my HF bike jack, getting the weight off the front wheel. Put the oil catch pan under the left fork. Unscrew the screw holding the oil in the fork. Note that on the right side, I had to use the impact driver tool I bought 40 years ago from Many, Moe and Jack. Oil pukes out mostly into the catch pan. Let drain a while. Now, the last time I did this, I bought a hand operated vacuum pump specifically for this purpose, so I dug that out, removed the Shrader valve from the front anti-dive air reservoir (crash bar in my case, probably handle bars in other's), put some tubing on the nipple, screwed a rubber cone shapped thingie that came with the vacuum pump into the bottom of the fork at the drain hole, put some vacuum line on the end of that. In momma's glass measuring cup, I poured just under 7 oz (spec 7.75 wet) of HD type E fork oil. Please tell me I didn't spend 17/quart for ATF in a HD bottle. Sure looked a whole lot like Toyota ATF to me. Anyway, vacuum line in the cup, pump the vacuum pump and pull the fluid into the bottom of the fork. When done, I kept pumping, pulled the vacuum cone thing and put the screw plug back in. Made a bit of a mess and lost a little fluid.

Here's where I started thinking. Always a dangerous thing. So, after whapping the impact tool to get the screw out on the right side and letting it drain, I dug through my refrigeration tools box and pulled out my HF air powered vacuum thingie. Hooked it up to the Shrader valve nipple, put the hose/cone adapter in the bottom of the fork, put some air on it and let it suck the fluid in with zero pumping from me. Undid the hose at the bottom of the fork, put the screw plug back in while the suction was still going with a tad bit of Never-Seize on it and that side was done with zero mess in half the time. I'm going to have to add this to my every-other-oil-change routine.

 

Check the book , my 08 uc says 50,000 . Put on the readers !

 

Book says 5K.




But then we were taking about MOTORCYCLES, not Pastry Treats.

 

This is the HF vacuum thingie:

https://www.harborfreight.com/air-va...ors-96677.html

$17. I bet, though, that with enough duct tape, you could get a plain shop vac to work. Just something to keep the vacuum going on the valve stem while you casually put the screw back in. Otherwise, you're fighting the screw and trying not to let the stuff puke back out.

 

 

 

Some google-fu shows the HD Fork Oil Type E to be 20W. There is apparently a Screaming Eagle fork oil out, and google-fu shows it to be something like 80W and there are some complaints when people put that in their bikes. Now, the original Hydra-Glide of 1949 vintage used ATF for fork oil, or that's what people put in it. This Type E sure looks like ATF to me, smells like ATF, flows like ATF. Let's just ASSUME you can use ATF in the forks. Redline makes several ATF oils. Redline D4 ATF has a viscosity of 35 @ 40C. Redline High Temp ATF has viscosity of 48 @ 40C. So, I'm thinking here... I wonder if the D4 ATF would firm up the front end a bit without being as brutal as the Screaming Eagle 80W? I just might try it next time, as I now change my fork oil every 5K miles, like the book says. And the Sportster book says to do it every 10K.

 

I have been using Mobil 1 synthetic atf for two or three riding seasons now. No issues, no complaints. Can pick it up anywhere. I like the way the forks feel on my Dyna 39mm forks. Specs and cSt conversion chart are listed in the links below. Nice tip on using a vacuum pump, thanks. YD

https://mobiloil.com/en/automatic-tr.../synthetic-atf

https://www.glennbennettcorp.com/hub...-Reference.pdf

 

According to your reference chart, I think that Redline heavy is going to be a little thicker than the Type E, and the D4 about the same. Looks like the M1 is about the same as D4. I have a quart of that on the shelf, actually. I use it in my primary, when I can find it. Also, the Redline meets GL4 gear oil requirements.

 

Question. Is type E a 10 weight? Thanks....