fork seal replaced

[stroscoach]

Hi all. just replaced my ft fork seals and they bottom out now when hitting larger bumps or pulling into driveway . My manual has 10w 30 as the got oil could this be wrong and causing the problem?

[Mark Olson]

sounds like your oil level is low .

did you measure it?

quick check is 120mm from top with springs out and forks compressed.

[stroscoach]

sounds like your oil level is low .

did you measure it?

quick check is 120mm from top with springs out and forks compressed.
I did measure it , manual called for 15.08 oz . I will check the level, thanks for the input

[SlowOldGuy]

If you're bottoming out, then you've got a spring problem.  

The spring is what holds the bike up.  The fork oil only controls the VELOCITY of the fork movement.  It has no effect on the position of the fork.  

Bottoming out is a spring problem (i.e. weak spring or not enough preload).

DavidR.

[carsick]

If you're bottoming out, then you've got a spring problem.  

The spring is what holds the bike up.  The fork oil only controls the VELOCITY of the fork movement.  It has no effect on the position of the fork.  

Bottoming out is a spring problem (i.e. weak spring or not enough preload).

DavidR.

What about the "air spring" effect of a higher oil level creating resistance to bottoming?

[Flying Scotsman]

Before I did  the seals and fixed a dampner rod on my 85 it would bottom out after I did them there great.So springs must hold the bike up but the oil must stop the amount of travel when you brake so the oil is holding the front end up when braking IMO.

[RichBaker]

Before I did  the seals and fixed a dampner rod on my 85 it would bottom out after I did them there great.So springs must hold the bike up but the oil must stop the amount of travel when you brake so the oil is holding the front end up when braking IMO.

Nope.... all the oil does is damp oscillations and control the speed of the suspension movement.  There is an "air spring" effect that is determined by the oil level, and that will help reduce fork "dive", but the springs "rate" is what sets ride height and bottoming resistance.  The OEM springs are fairly soft, too soft for most normal-sized riders.

[Mark Olson]

guys , the original post was he changed his seals and now it bottoms out.

so either he did not set the preload correctly or the oil level is to low.   Also he is using motor oil .

[movenon]

Had the same problem with my 1990 FJ. At any rate it "clunked" or banged pretty hard going over a curb. The bike was new to me and it was just another part of trimming it out. I drained the oil and it had 8 oz plus or minus a bit in each leg. Manual spec's 10w fork oil or 30 w motor oil, or 10-30 weight motor oil (equals about 15 W?).
I'm not a small guy so I used 10-30 motor oil and set the preload up to max setting. Installed 14 ounces of oil in each leg. Works great now. No problems. Think I will now take 1 setting off the preload and do a test run next. The fork seals seem to be holding good with no leaks, when I found only 8 oz in each my thought was probably bad fork seals but no problem there. Oh, after the oil and preload change I did a sag check. It came out good. My front springs were the stock progressive type.
I set the rear up to max preload for the time being. I am still playing with the settings. Seems to understeer a bit but that hasn't got anything to do with the fork oil, preload etc.. Have a good day

[stroscoach]

guys , the original post was he changed his seals and now it bottoms out.

so either he did not set the preload correctly or the oil level is to low.   Also he is using motor oil .


Is using motor oil not good ? I had a friend who worked at a bike shop do the job for me he said the adjusters were frozen so he would have to keep it at the same setting but something has changed I can hold the front brake and with a little effort I can bottom out the frt end couldn't do that before and there was only about 4 to  5 oz of oil in each fork when we originally drained them. my first thought was wrong oil. Thanks I appreciate your input

[Travis398]

It's not the oil ( so long as you put enough in)

[Flying Scotsman]

If you have 86 forks with anti dive they should be the same as my 1985 I use 10W30 in them.My 90 has later shocks and 10W30 isnt spec I think it was 15W fork oil.My horn used to hit the fender brace but the forks were just about empty.There good now.
What year is your FJ ?
I would take them apart and do it again something seems wrong or try more oil first so theres less air in there.
Mr Baker makes sense with the  "air spring" effect"
I have a lot to learn about suspensions.

[JFox]

The easiest way is to change the oil. You have to use fork oil 10W (originally), or heavier (if you are quite large sized ). You will see the difference at once. Or may be not...
Did you mount the legs properly? I mean, there is small part at the bottom of tube outer - SPINDLE, TAPER.
If its in wrong position only springs works. Like you would have no oil. Its worth to check.

[markmartin]

It's not the oil ( so long as you put enough in)

+1

sounds like your oil level is low .

did you measure it?

quick check is 120mm from top with springs out and forks compressed.

+1

Did you mount the legs properly? I mean, there is small part at the bottom of tube outer - SPINDLE, TAPER.
If its in wrong position only springs works. Like you would have no oil. Its worth to check.

We may have a winner....

I'd go in that order.  At least you'd verify what is is what should be.  Let us know how it goes, and good luck.

[movenon]

I stand corrected. I put 15 oz oil instead of 14. And that was 120-130mm measured from the top, no spring, fully collapsed. Check your oil level first.  Rest to , ride tomorrow