Front Air Shocks XJ1100J

[Txsbigfoot]

Now for my next problem on my bike is as follows. I noticed the front forks make noise and checked the air pressure. It was zero of course. I hooked up my compressor and it took about 1 second for it to go to 25 lbs and bleeds down awful fast. Within two seconds with a guage. Apparently the shocks are not getting the whole air supply. Although they did seem to work better. After a day I checked the pressure, and guess what? Right. they were on zero. Any suggestions on where the culprit leak might be? I have an XJ1100J. Trying to get all the bugs out of the bike as it runs like new.
Thanks
Mike

[JohnSg]

Just a guess since I've never actually worked on them but I think the only places the air could escape is the oil drain plugs, fork seals, and the Schrader valves (where you put the air in). My first instinct would be bad Schrader valves.

The air fill on my '79SF are seperate so one could go down and the other still hold. Does yours have an interconnecting tube where they equalize? If so, that would be another place to check.

[John]

Check the O rings inside the large banjo fitting that surrounds the top of each fork tube. It is in the air line. There should be an airtight seal there. Use a spray bottle with a soapy water solution in it. Blow the forks up, and spray everywhere with the solution. Where you see bublbes forming, you have a leak.

[Jerry]

Manual warns not to go past 17 pounds pressure. Use a bicycle tire pump. The forks are tied together with a balance tube.

In the long run, you might want to change to progressive - rate fork springs. Progressive and Hagon both offer them. People who have gone this way, including myself, no longer run air in the forks. Not necessary.

Remember the air pressure 'pre-loads' the forks and determines how much initial force will be needed to get the forks to move. More pressure, less 'give' for smaller bumps and expansion strips. Less pressure, smoother highway ride with more supple suspension. Progressive-rate fork springs are wound so compressing the springs the first inch or two takes less force than compressing them the next few inches.This combines good highway suppleness for small bumps with increasing stiffness as the suspension loads up, such hitting larger bumps or settling down in a fast corner. Stock springs are not progressive, and adding air does not change their rate.

Remember you are working with 22 year old suspension components that need to be upgraded anyway; the springs are most likely out of spec by now. With new springs ($120 - $150 installed) and a Tkat fork brace you will be pleasantly surprised at how much better that XJ can handle!

[Txsbigfoot]

Ok I can handle the new shocks Jerry. Are you sure about the springs costing less than $200? Is that factory installed and you speak of progressive springs, would the people in my area know what you are referring to? If you have part numbers or such let me know.
Thanks
Mike

[Jerry]

I'll see if I can dig up the part number. In my case, I had the springs installed by Progressive at a bike show. Year was 2001. Cost at that time was $125.00 installed. Install included fresh fork oil but not seals.

The springs were not XJ specific; they are XS springs with a piece of PVC tubing on top to make up for the extra length of the leading axle forks. (Early XS has axle going through fork legs.) The length of this PVC will depend on your weight, accessories (I weigh 250+ and have a Vetter mounted) and will be between 2.5 - 3.5 inches. The longer the PVC the more pre-load is on the springs. Progressive springs come with an instruction sheet that gives recommended lengths for different loads.

Any reputable shop or independent mechanic should be familiar with Progressive fork springs. Progessive is a major supplier of motorcycle suspension components, and their stuff is available from Dennis Kirk and many other outlets.

Other key, besides getting the right preload from the PVC insert, is getting the right amount of fork oil. When Progressive did mine they used the oil level method, not volume. They filled each fork to a level specified in the manual (210 mm from top of inner tube, fully compressed with no spring in the leg) as wear in the tubes requires a bit more oil than the stock value of 8.45 ounces. I opted for their multi-weight oil, but the stock spec is 10 weight.

My set-up is a little stiff when cold, but settles in nicely when the fluid warms up. I'm using stock Yamaha fork seals.

On another note, the XJ has a brace built into the front fender that acts as a fork brace, so adding a Tkat brace doesn't have have as much impact as it does when added to an XS. Still noticeable improvement, though, and I recommend adding one if possible.

[Robert Haller]

Jerry,

I'm planning on ordering Progressive fork springs for my 79 Special and wondered if it matters which end the spacer goes in and how the springs go in. You answered the first question by saying Progressive put the spacer on top. Did you see whether the tighter wound spring end went at top or bottom?

[Jerry]

Tighter wound end goes on top, nearest handlebar.