Hello,

I bought my XTX in may 2013 (my first bike). One of the first mods i dit whas the Kev spacers in the front shocks. I good improvement for the handling.


I did a lot of riding and i improved my riding skills. (I did a supermotard course).
I drive faster through the corners and have more lean angle. I notice that on a corners with a couple off little bumps the bike seems lozing grip on the front wheel. (rinding above 60km/h) It feels if the bike is bouning on the front wheel (it's not really bouncing but it feels like it). Does someone recognized this behavior ?

I was thinking the stock spring with the preload (kev spacers) can't handle the little bumps.
Would replacing the frontsprings with Hyperpro or Wilberd do the trick?
Any advice is appreciated

Sounds like you could be suffering from what’s known as “chatter”- the handlebars feel like they’re jumping about in your hands crossing ripples/ruts in a corner? Google it, there's plenty of info out there and see what the symptoms are and if they're similar to yours.

Often the most common cause of chatter is insufficient rebound damping, although it could be a combination of too much preload or a spring of too higher rate.

The first thing I’d point a finger at is your fork oil. When was it last changed? When was the level/air gap last checked? Is the correct weight of oil in there? If it’s a second hand bike you bought and you haven’t had the forks out, these three questions are going to be pretty impossible to answer.

The addition of extra preload (fork spacers) tends to show up weak rebound damping as, although the springs haven’t changed in rate, they have more stored energy which will be dissipated quicker when they are unloaded, putting the rebound damping under additional strain.

Changing the fork oil and checking the air gap/level is a cheap and relatively easy thing to do; it’s a good starting point and may well yield positive results. If doing this doesn’t make a difference, you won’t have lost much and can then turn your attention to the more expensive bits (springs etc), knowing you’ve ruled out the simple/cheap things first.

Of course, I’m sitting here hundreds of miles away never having ridden you bike, so to a certain extent the above is educated guesswork, but nevertheless it’s probably worth a try…

__________________

Hi Pleiades,

Thanks for the fast reply.. :-)

I googled for 'chatter' and i think that's it. The shocks don't follow the road but just bouncing in a ritme. But i read some articles that chatter happens a lot when the Motogp riders really pushing the bike.
I wasn't really pushing the bike at the moment it happens. But maybe the little bumps in the road triggered the chatter.

The bike is a second hand. I drove 7000 km with it and never checked the shocks. I don't know of the previous owner did some work on them or changed the oil. Or did no maintenance to it.

The milage is 21.000 km at this moment. So... i think it's a good time to do some maintenance on them.
The Kev spacers work great. But i think i'am pushing the bike more and more lately. Maybe its a good idea to change the springs with some progressive springs during the maintenace.

I looked in my maintenace book, but i can't find where the position is of the air gap of the shocks. (I can not find it on google). I always thought it was a closed system. Can you tell me where the air gap i located.

The "air gap" is effectively the space between the surface level of the oil and the top of the fork tube when the fork is compressed fully and the spring is removed. It should be 125mm on the XTX.

The trick is (when you've removed the forks from the bike, removed the springs, taken off the caps and tipped out the old oil) to invert them and pump them several times to get everything out. When you've done that get them the right way up and push the fork tube down as far as it will go. Fill with the recommended amount of oil (600ml on the XTX) and then lift the tube up and down again, pumping the oil through the fork internals. Finally push the tube fully down again and measure the distance from the top of the tube to the surface of the oil. This distance should be 125mm. Pull the tubes back up, refit the springs and caps and you're good to go.

The air gap's job is to make the forks progressively harder as they compress, the air working like an extra spring as is compresses and resists further travel. In fact all forks are progressive because of this, even if they have linear springs. You can play about with the air gap size to alter the progressive nature of the fork's operation.

Kev has done a walk-through with pictures here... http://www.xt660.com/showthread.php?t=4274

If there's one thing I've learnt about suspension, it's that you are well advised to do one thing at a time or you'll never be able to keep a track of what changes are making a difference. Service the forks and see how it goes, then do the springs if you feel the need. If you check/change the oil and fit springs, you'll never know which which causing the original problem.

Bear in mind that your problem may even be down to the rear end - one thing can affect another. Not always is something felt at the front caused by the front. Again, look at one thing at a time and leave the rear for another day.

In the meantime I'd give linear springs some serious thought too - do a bit of research. Progressives are notoriously difficult to set up right, particularly the damping as its almost impossible to get one weight of oil to match all the variations in rate along the spring's progression. Setting sag can be a bit of a minefield too.

__________________

Suspension is a personal thing what works for you has every chance of not working for the next guy though he might be the same height and weight and in reality there are no rules,hence why when you read on the net about an owner going to suspension guru who set the bike up for �25 it's just silly.

I run two bikes with Ohlins and another with Wilbers but strangely enough I rather like the basic suspension on the XT and at a touch over 76kilos certainly do not need any different spacers in,it feels over sprung as it is,and in an ideal world could do with revalving,but for me it steered slow and hence why I dropped the forks through the yokes,Kev's spacers will sit the bike up and slow the steering unless you counter that.

I'd take the spacers out and keep them for your own R+D,buy an aftermarket set of fork springs and the experiment with different oil viscosities and amounts,with my Triumph Tiger I ended up with Ohlins fork springs went from 5wt to 15wt and increased capacity(because I ride two up on it a lot) but it's all down to trial and error and to get an exact set up you'll need one of these.

http://www.dirtbikebitz.com/motion-p...ce=GoogleBase1

Do not forget when doing a test you'll need to ride 30k's at least to really warm the fork oil up so you have some idea where you are.

as above... start with the correct springing for your weight and try diffrent grades of fork oil
But putting spring spacers in rubbish forks.. just makes harder sprung rubbish forks..
the damping is not able to control the standard springing... So putting preload spacer in only makes the damping less effective..

Gold valves & the correct springing for your weight...
Or
fork replacement with the correct springing for your weight..

not sure what the hot set up for a motad is..
dirt... 35mm static sag / rider sag 33% of travel.
Road... 10mm static sag / rider sag 20% of travel..
So Motad could be somewhere in between..??????

If yer get the front sorted... you will then notice just how bad the rear shock is...

__________________
Harley Davidson..
The easyest way to turn gasoline into noise with out the side efect of horse power...

Thanks for the advice.
I will start with the basics and work from there.

Here's an update,


I checked the oil level in the fork. That was okay. The oil had a nice transparent red color. The seals were okay. So I guess it was okay. I adjusted the rear spring in a different setting. The hardest setting was a little bit of an improvement. But my length is 1.73m, so my feet were just touching the ground.


I oderder some Hyperpro springs, that's a great improvement in my situation. The corner with the little bumps is not a problem anymore. The understeer in high speed corners i gone.


Thanks for the help everyone.