Stiff front suspension problem

[bugboy]

This 87 fj I bought has a really stiff front suspension.  Every little bump comes through to the handlebars and it feels jumpy around corners.  I looked in the manual and as best as i can tell, the preload is set to the lightest setting.
I've been looking through old posts that talk about sag and fork travel.
I put a zip tie on up against the fork seal and then sat on the bike and only got 5mm deflection.  I rolled the bike forward and grabbed on the front brake hard a few times and only get 30mm deflection (from just sitting on side stand).
As the bike is sitting on the side stand I have 90mm from fork seal to the fork clamp above.

PO said he put in progressive springs, 10-15wt oil, and had it set up for him (300 lbs).  I'm 160 lbs and the front is way too stiff. 

On my old '89 if Ipushed the bike forward and grabbed the brake I'd get a whole bunch of deflection.

What should I look at to solve this stiff front end?  The PO suggested I go to 2.5 wt oil.

[andyb]

Sounds like he's got a very stiff spring in there or too much preload.  Pop the fork caps off (they will be likely under a lot of tension, so they will pop off with some force, be warned).  Look to see if there's a spacer at the top or bottom of the spring, if you find one, remove it.  If there isn't, check to see that things move through their travel without binding up.  With the springs out and the forks bottomed, measure the amount of air between the top of the fork and the oil and report back (or search, the spec you want is someplace).  Then reassemble.  If you didn't find anything, it'll be time to order new fork springs, I'm afraid.

[Mark Olson]

change your fork oil first and make sure it has the right level and weight in it. progressive springs would cause this stiffness problem unless additional spacers have been used.like Andy was talking about.

see what is really in there as P.O. 's have been known to be creative in their mods.

[bugboy]

I'll put that on list right behind:
Valves and carbs / tune-up

I've got 1 each Clymer and Haynes manuals on order.  I'll get busy once they get here.

Thanks.  I look forward to my time on this board (and maybe even a rally if time, $$$ and FJ project completion permit)

Kurt

[markmartin]

If the '87 fork is like the '89 forks, the damper adjuster rod can get installed with it's tip in the wrong orifice.  There's a 'D' shaped hole in the middle of the top of the damper rod.  This is where the D shaped  adjuster rod is supposed to go.  This D shaped hole is surrounded by slots around the perimeter of the damper rod.  The adjuster rod will fit into those slots but not allow the rod (and consequently the fork tube) to slide when compressed.  I've made this mistake, and my forks felt like what you are describing.

If this happens to be your problem, it is easily fixed by removing the fork caps and insuring that the D shaped rod is inserted in the D shaped hole during reassembly.