Would it make sense to add slightly more fork oil to make the ride firmer, or would the seals just blow out?

 

If you were to put more oil in,it will not get you where you want to be.Maybe progressive springs.Or try the next weight up on correct amount of fork oil.You do not want to have hydraulic lock.

 

Hadn't thought of heavier oil. Thanks 01fxdxt

 

I read somewhere recently that fork oils can be very different in viscosity, across brands. If you know what brand you currently have, then by all means try a slightly heavier grade. Do bear in mind that our forks have very rudimentary damping mechanisms, so may not be very sensitive to 'fine tuning'!

 

In an emulsified system that you have, you can either add fork oil or pressurize the fork tubes with an outside source such as an air pump. A fork tube stroke in an emulsified system can be effected by altering the air spring. An air spring is the space between the fork cap and the fork oil. If the fork cap is open the suspension is relying on just the physical springs. Close the fork tube and you have the air space captivated and sealed.

As the fork compresses the oil does not compress but the air inside of the air spring space does. Ignore the explanation of bushing wear in the illustration but look at the space between the oil and fork cap. In order to take advantage you must seal the top of the fork tube and pay attention to the top mounting bolt by using Teflon tape.

As the air is compressed as the fork compresses the fork movement is logarithmically slowed hopefully to a stop and not bottoming out. Here is a graph showing how, by adding 10mm of fork oil per Dyno run effects the dampening on my 30mm cartridges and your forks.



Adding compressed air: By adding compressed air such as done up to 2001 in the FLT's is a very effective way of changing/adjusting the top part of your stroke compression. You must seal the fork cap and fittings a HD mechanics and end users failed to do causing leak down.

Adding heavier fork oil. By adding a thicker fork oil you slow down your fork movement, an unwanted result. The forks should move the absolute fastest as it can and without any introduced stiction as your fork already have too much friction by your bottom bushings riding over the aluminum Showa slider. By welding and re-drilling the damper rod compression holes (small ones) the compression oil flow is slowed down, a much better solution. Tossing the OEM fork springs and putting in the correct value ones will work better for cheap money. I never use progressively wound springs but use linear wound. The OEM progressively wound springs compress through the "softer" part of the spring just by adding riders sag. The MOCO has reduced your stoke some but this part pushes the wheel down on rebound. A better solution would be to increase the length and decrease the value of the top out spring.

I hope this information helps someone.

 

Which fork springs do you recommend?

 

I used Race Tech single-rate, which are available in several spring rates to suit different rider weights. They have a calculator on their website.

 

I think you need to define "firmer ride" more clearly. I think what you really are thinking of are firming up the springs, not slowing down the dampening or rebound.

A cheapo solution might be by stuffing some spacers in the fork above the springs, e.g. some washers or old coins. On an old bike where you are not after sports performance, you may well save yourself $98 for the sake of a $1 worth of parts you already have kicking around the garage.

The effect you are after is stronger springs, you probably want to retain lighter dampening to make them react quicker to bumps, e.g. lighter oil. Putting a spacer in does not make them stiffer but preloads them or takes off some of the weaker spring rate where they are progressive wound.

It's very a 'old school' solution. How much? Don't know ... I'd start at 1/2" and keep going up until they stop pogoing all over the place. Just add a couple of washers each time. I'f you give me a couple of hours, and don't know, I'll tell you what size.

 

Harley makes a regular and a heavy fork oil. Most people who go to the heavy fork oil learn to hate it. They say it rides too hard. I have Progressive springs in my FLHTC and love them. That's what I would suggest. Progressive springs and standard weight fork oil give a really nice ride.

 

Before I got the Ricor units I ran the Progressive springs and a 50/50 mix of 10 wt and 15 wt. It gave me what I was looking for, ride wise.