Fork Travel Distance

So i have a 1980 xj650. i recently got a used set of forks from the local bike parts store/junk yard. i believe they are off of 81 because they have the air nozzle for preloading. so my question is how far should my forks travel? i havent ridden on them yet but when i sit on it they compress a fair amount and it seems like i can compress them too far just from pushing on my handle bars. if they are too soft does it mean the fork seals need replaced? or just change the oil?

 

Could be bad seals, or oil viscosity. If you change the viscosity, you have to change the seals anyway.

Another upgrade would be progressive springs. You can mess around with preload as well.

When you open up Pandora's box of fork tuning, it can get a little complicated. Easiest thing to do it pull them apart, up the oil by 5, replace seals, and give it a try again.

 

It's quite common for the original fork springs to take on one heck of a sag. Seals only need to be replaced if they are leaking.

 

If they've got the Schrader valves they should be '82 or '83 (assuming it's an XJ Maxim fork).

Travel is 150mm, 5.91".

Assuming NO air in the forks - Spring rate is 26.6 lb/in first 3.94" and 35.1 lb/in after that (dual rate springs). They have almost 1.5" preload so it should take about 40 lbs. per fork to move them from top. There is probably at least 80 lbs. of bike weight on them so they should be sagging a bit from the get go.

Once they're off the preload it should take ~ 53 lbs. force to push the nose down an inch.

You can make them stiffer by putting up to 17PSI air in them (both sides equal).

Apparently you have no idea about the fork oil in there. I'd suggest replacing it. You will be very happy if you drop a set of progressive springs in while you're at it.

 

thanks for your help guys! ill look into the PSI, oil in it and even a set of progressive springs depending on how much they cost. Any good places i could get a set?

 

Progressive suspension is the brand, they should be on ebay for sure.

 

XJ4Ever, top right logo on this page, click it, or PM Chacal. He can hook you up!