I have a 1991 FLT that I want to change from a air ride front forks to a hydraulic fork. Has anyone else done this? What I'm wondering is can you put regular seals in those lower legs or do you have to change out the whole lower leg?

 

I haven't done this, but I'm heading in that direction. Here's a good website that will answer a lot of questions: http://motorcyclemetal.com/gpage1.html

 

I did the progressive mono tube in my 97, worked great

 

Bill, you already have a hydraulic fork, with extra 'air assist'. We can adjust air pressure to supplement the wire springs, which helps to adjust for different rider weight, ar adding a passenger. In addition, there is an integral anti-dive feature. All that sounds great and fairly hi tech, except that it is decades out of date and was never quite as good as it promised!

The least you can consider doing is to dump all the air stuff and add a fresh set of springs, such as Race Tech, to match your weight. They alone will improve ride comfort a little and leave you with exactly the same hydraulic damping the forks currently have. You can make small adjustments by using different brand/grade of ffork oils.

I have no experience of Progressive, but as your namesake at post #3 points out, they sell a new and different style of fork insert, which replaces the stock damping mechanism, but they don't offer matched springs AFAIK. I've upgraded my own forks to Ohlins cartridges, but that isn't a simple bolt-in.

 

This is mostly about taking away...you take away the air manifold that spans between the forks, along with the solenoid and valve stuff.

(One fiddle I ran into: There is a ground block attached to the manifold. You'll have to relocate that.)

The forks themselves are fine. As long as you're in there, a fresh set of bushings and seals is a good idea.

 

I found happiness with Progressive springs (you gotta be big to use their heavy duty) and Intiminators.

 

The air ride is actually air over oil. You have the hydraulic system same as everyone else but you have added air under pressure above the oil. This is usually controlled by pressure that is added at the end of the handlebar making the handlebar a reservoir for the air system. Under normal conditions you ride on the air. When you hit the brake switch your anti dive solenoid between the fork tubes and handlebars will close off the handlebar reservoir and keep the bike from diving with he front brakes applied.

personally I liked the system on my '89. I do remember 1 time taking the anti dive solenoid apart to clean the ports where the solenoid closes off the handlebar reservoir.

To remove the system you only need to remove the anti dive solenoid and hoses between the dfork tube caps and handlebars. But i think you will be looking for stiffer springs or increasing viscosity of your fork oil.

 

My 89 flt has air in the handlebars. It has a leak so much of the time I run without air with no problems and a soft ride.

 

Compare RaceTech single rate springs when you look at changing over from air. I’m running them with 10wgt fork oil, nice and smooth ride.