Forks bottoming out

[kapebretoner]

I broke my plunger case and anti dive unit on my left fork. Bought a used one. i installed it and while I was at it I installed new seals, bushings plus new fork oil. Out and about on my bike and i notice that my forks are starting to bottom out. I adjusted the anti dive switch on the left side of the bike up to number 3 setting. I but 14 psi in the front and 21 psi in the rear. Front does not hold pressure.. I have oil leaks. i put in 400 ml of fork oil. I only did one side because it cost $130 to do one side. Any ideas or suggestions.

[bongobobny]

OK first, that "dampening" adjuster on the side of the bike is for the REAR shock only. Also, 21 lbs in the rear is pretty low, I used to run around 40psi or more.

 

400 ml sounds like too much oil, if I recall right I was using somewhere around 360ml. 14psi in the front shocks is on the high side, the Maximum air pressure for the FRONT shocks is 17psi. The REAR Max pressure is 72psi I think.

 

OK when you replaced the seals did you use authentic Yamaha seals or aftermarket?? Aftermarket are KNOWN to leak! Another thing to consider is how smooth or how pitted are the tubes?

 

The most common reason front forks bottom out is the springs are just plain worn out! Spring rate can change just from age being somewhat compressed at all times with the bike just setting there. I can't remember the exact price, but a new set of "Progressive" brand springs goes for less than $100, around $75 or so. Of course that's US funds, in Canadian dollars that's probably a half a bizillion give or take...

[yamagrl]

$76.63 free shipping in US. Canada shipping and import adds about $25.00

 

http://www.ebay.com/itm/Progressive-Suspension-Fork-Springs-For-Honda-Kawasaki-and-Yamaha-11-1112-/361274075221?hash=item541d9ce855:g:PPwAAOSwqv9V51N7&vxp=mtr

 

 

US dollars, Canadian Dollars... Just numbers that reflect the universal value. Change to yen, you get different numbers again.

Edited May 11, 2016 by yamagrl

[bongobobny]

There ya go!! That Heather is right on the ball!! The last set I bought was about 5 years ago so it looks like the prices haven't risen much...

[yamagrl]

I bought a pair last year and that's about what I paid.

[cowpuc]

IMHO,,, playing with the anti-dives, replacing fork seals and bushings, setting up the forks so they will maintain air pressure and putting in new fork oil are all wonderful things to do BUT - if your springs are sacked (and it sounds like they may very well be) alllll that effort is for nought..

1st thing I would do is go out to the bike, release any remaining air from the front end, have someone lift it up off its side stand and take a look at how much travel you have left in the forks. You should be seeing 3 inches or so from the bottom leg top surface to the wear line on the fork tube if the springs are good. I have purchased a number of these 1st Gens with very low mileage on them and have ALWAYS found the stock springs to be sacked and sacked from sitting - not from being "used".. It's a fairly common thought that sacked springs can be over come by adding air pressure, adjusting anti dives and maybe going to a heavier weight fork oil - IMHO,, not so much.. High air pressure is hard on seals, anti dives are in place for setting the bike up for excellent braking (especially for folks who use the front brakes in cornering), and damping thru oil weight is more of control device for how quickly your springs rebound or compress..

If your springs are sacked Kape (and I gotta hunch they probably are) what I would do is pick a set of Progressives up (Ebay CHEAP), pull the oil from the forks, pull the stock springs and those tubes that are on top of them, drop in the progressives and proper amount of Bel Ray 12.5 weight (thinking Bob is right - 360ml sounds about right), add 3/4 inch of preload spacer on top of the springs (some folks like 1/2 but I prefer 3/4).. I know from doing this your air leak wont matter any more cause you will never need air in the forks again, set up like this will be a LOT easier on your seals because the front end will now be supported by springs like its suppose to be instead of putting undo stress on the hydraulic system within the forks and you will be amazed at how well it handles.. I would also suggest going back and match set your anti dives..

[Patmac6075]

I just redid my entire front end and Puc is right! Them springs is just about worthless! I couldn't believe how thin the coil was and how spread the coils were compared to the progressives. There is a world of difference....

FYI, I used 360ml of 10wt. fork oil and I am experiencing a pronounced "pogoing" at slow speeds (solid as a rock above 50mph), I would definitely recommend 12.5 or 15wt. fork oil if you make the swap.