Fork Oil

[otis71]

What is the a proper fork oil replacement for Harley type B? The dealer never stocks the correct fork oil for earlier front ends. Thanks.

[DEEBS47Chief1991]

I have used automatic transmission fluid (about 7 weight oil) for 40+ years in all kinds of forks with good results.

[dukekleman]

Otis71,

I would recommend using a 15W Fork oil or heavier on the HydraGlide fork assemblies.

The fork oil viscosity is typically changed with spring rate changes.
I use the Screaming Eagle Heavy fork oil quite often.

I have seen aftermarket fork springs vary a lot in spring rate.
I would recommend either Eastern brand springs as an economy level and Race Tech springs as a high level tailored ride.

Hope this helps,

Duke Kleman

[droptopford]

I have used automatic transmission fluid (about 7 weight oil) for 40+ years in all kinds of forks with good results.

+1 on the transmission fluid. Been using that for a long time too. Don't know anything about spring rates or the wt of the fluid I used. I know it's Type-F though, and I actually started using it as an experiment.

Many years ago I bought a Hydra Glide with a slight fork leak. I drained it and replaced the old oil with Type F along with some automotive transmission leak-stop product. Rode it that way with good results... good fork action and no more leak! Been using the Type-F ever since.

Edit: Certainly not suggesting it's any better than the recommended Genuine H-D fork/Screaming Eagle stuff. It's rarely in stock though and it was outrageously priced last time I checked.

Edit #2: Also should add that I tried the stop-leak solution on my Softtail fork when it started to leak. Didn't work for ****!

[tomfiii]

Screaming eagle oil being heavier you will feel those sharp bumps more.

[dukekleman]

On the old 49'-77' dampening system design, the compression dampening effect is very minimal. The heavier weight of the oil helps the rebound dampening system control the spring rate better during rebound.

If the spring rate (compression & rebound rate of the spring) and Spring Pre-load are not properly matched then you'll feel those sharp bumps only if the spring rate is to heavy. This is the exact problem I see with some aftermarket springs, the rate is to high (Stiff) and/or too much Spring Pre-load.
The rebound top out is the worst, a loud metal on metal bang occurs. This is due to the absence of a Top-Out Spring and the imbalance between valve dampening, spring rate and oil viscosity.

Hope this helps,

Duke Kleman

[DEEBS47Chief1991]

I found the correct oil. Not a bad price either.


Fork oil.jpg

[otis71]

As far as screaming eagle being heavier I know the factory recommended type B is heavier than the type E so the screaming eagle is probably close. I ended up buying 20W to see how it feels.

[marksg]

I had 30w recommended years ago and have been using it with good results.