05 FLHTCUI with 30K on it...had it a month.
Setting it up for my comfort...

Figure the fork fluid has probably never been changed. I drained all the fluid out, one fork at a time.
Right fork, 10.8 ounces went in just fine.
Left fork, had to pour 2-3 ounces at a time until I got the "sucking" sound from pumping the forks.

I used heavy 20wt fork oil from Drag Specialties, I am 260 lbs and when my passenger is along, we're 400lbs total.

HUGE difference on the small bumps, braking, etc.
However, when I hit larger or square edged bumps (driveway approaches, etc.) the bottoming feels like my fillings are going to fall out. It's bad...
They never bottomed like that before with the old fluid, they were just real soft...too soft.

So the question is... More fluid, less, should I drain it and go with SE 15w oil? (I originally intended to, my local dealer was out of the SE 15w)

I like the small bumps and lack of front end dive, but there's no way I can tolerate square edged bumps, etc.

I know the absolute, 100% best way is to remove the forks, disassemble, clean, measure height, etc. I'm really trying to avoid that until season is over.
All I wanted was a stiffer ride and not to bottom like they are now.

Ideas please?

 

Hi Dave,

My modest experience with forks is that the viscosity of fork oils is very variable between brands, in fact it is a bit of a lottery! In other words it isn't safe to assume that two brands of the same grade will behave the same. For a short-term fix I suggest you check which grade of Harley fork oil is specified and simply use the next stiffer grade of the same brand. In any event 20 grade does sound too much!

What you describe is entirely consistent with the oil being too heavy. It moves reasonably freely through the dampers on decent surfaces, giving you the feel you want and like, however when asked to dampen a bigger change in the surface, cannot flow quickly enough through the damper, hence the jarring sensation you experience.

Having used 20 grade oil you could alternatively change to say 15 of the same brand, instead of my earlier suggestion. The reason for the difficulty of filling one leg is that your forks have different devices inside each leg, so the space available for filling them is different in each leg.

As an economical solution to consider for the future, there is a lengthy thread by fabrik8r here, about an attractive upgrade, which I am doing myself. This involves replacing the original internals of your forks with single-rate springs, matched to your weight, plus custom-tuned Ricor Intiminators. For your bike you may have to buy a few internal parts, so the damper rod is the same in each one. The magic formula includes the recommendation for Amsoil fork oil, grade 5. Don't be put off by that low number!

That link includes instructions on modifying Intiminators yourself, to enhance their damping characteristics, but fabrik8r has also offered them for sale pre-modified by himself, which is how I got mine. He may still do that.

Hope that helps!

 

Thank you sir...we're on the same page.
I'm going to a different dealer today to pick up some Screaming Eagle 15W.
In fact, I may pick up one bottle of 10 w and one of 15...and mix the two.

I'll read up on that thread in a bit. As of now, have a few other musts I'm looking to buy... but I already have an off season list started...

Thanks again Graham. It is much appreciated.

 

So changed it out this morning. All set now.
I just have to tinker, so I put in 8 ounces of SE 15w oil and 2.8 ounces of Type E.
Dealer had B and E...I asked which was heavier, they gave me E. Come to find out B is heavier, so be it.
Regardless...
MUCH improved. I just over thought things and went overboard with Heavy 20W in each leg.

Less brake dive, good feel over small bumps...and no more Metal to metal bottoming feel.

KISS...sometimes we all over think things. Thanks again Graham.

 

My pleasure Dave - glad 'we' cracked it!