Front forks bottoming hard on any landings

Ok my forks are bottoming so hard it sounds like the steering stem just broke off. I am 6'3" 265lbs and I have the springs for my weight and I have had gold valves put in and still have this problem. The front forks fell super nice any other time but not when I land! Ouch! I have a 99 YZ400F and love this bike (i.e. that means I dont have the money for and new bike and I wont get a loan for a bike) I really do like this bike I just want the forks to give me a break and I dont me break my wrist! I have also heard that this is kind of problem on early YZF bikes. Let me know what you guys think because I looking into getting some different front legs. Thanks

When was the last fluid change and what weight oil was used?

Whats your fluid level at?

Are your clickers backed way out?

Seals leaking?

thats the obvious stuff, start there and then consider other (ie... stuff that costs $$) options.

Just had new fork seal put in and the oil weight is the Yamaha stuff and I have tried all of the clicker settings. I didnt set the level the guy that didnt the forks did.

Does it bottom with the compression clickers all the way in? If you have springs set for your weight then it should not be bottoming with the compression cranked.

Doesnt the Gold Valve change the compression characteristics of the mid-stroke? maybe they are allowing the midstroke to travel too easily and killing the end stroke...... I dunno:excuseme:

Hey YZFan,

In my opinion, if you are bottoming out and now blowing the seals, to try increasing your Fork oil level. Also, I dont know about the Yama fork oil, but I personally run Motorex 7.5wt. My cousin and I made the mistake of not properly filling because someone had told him to fill the fork fluid to the weep hole inside. I finally got the book for it, and read that the fork oil should be 5.12" or 130mm(if you have the tool) down from the top of the tube. I notice that since we originally filled to the weep hole that the suspension was much stiffer than before we changed it. 2 weeks ago, i undershot a triple step-up, and landed soooo hard every bone in my body felt the impact, and thought I was headed over the bars. Of course my left fork seal blew, and fork oil was running out like a faucet. So this time when I rebuilt it with my cousin, I was able to get one of the guys sent me the post to the online manual, and I checked it, and we were wrong about filling the fluid to the weep hole, matter of fact, it was about 3" less. I drained the fluid out of the other fork and rode this weekend.... OMG, what a difference, I have my suspension back, and its nice and plush. Granted, the manual says to fill 5.12" from the top, but we measured 4.75" because to allow a slightly stiffer front end, because I am about 195 lbs without gear. So, in my opinion, I would recommend increasing your fork fluid, and getting rid of the Yama fork fluid and try using the Motorex stuff. They come in 5wt, 7.5wt, and 10wt.. A lot of the guys I have talked to swear by the Motorex 7.5wt...

Just my .02 cents

I always run about 4.5" on all the 46mm Yamaha forks from 96-03 to resist bottoming.

Most likely you dont have the proper amount of oil in the forks.

YZFan, you must raise your oil level! I'm only 160# and I had to raise my stock oil level to prevent bottoming when I screw up (i.e. face a landing). I've got the oil level tool and you're welcome to borrow it. Since you weigh a bit more than the average guy I would say make a relatively large change. For example try somewhere around 100mm instead of the stock 130. It will make a very large difference.

i've switched to mobil 1 synthetic trannie fluid,it is 7.5 wt and helped bottoming alot. i run mine at 4'' from the top but thats getting kinda close to the max. try it at 4 1/2" and see if that helps. drain all the old fluid and run kerosene through the valves cycling them until they empty out let 'em drain upside down for awhile and following the manual fill 'em back up with the mobil 1 trannie fluid. its available at any auto parts store and it will NOT hurt anything in your forks. it adds a little more resistance to bottoming than the 5 wt:thumbsup:

ATF is not the best thing for forks. IT has a lot of detergents to clean things. So if you get a seal leak, it will be noticed!

You can pick up any wieght fork oil at local MX shops.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now