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good job covering all bases in your description


Different people often have different ideas on what 'chattering' is. Can you describe exactly what your front end does/feels like when it chatters?
 

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Well, this is by far not the only explanation for the problem, but I think it's very likely your springs and oil weight have alot to do with it. The stock suspension is undersprung for your weight, but the air gap (as determined by fluid level) is small. So you're undersprung at the top of the stroke, and progressively oversprung (due to the small airspace being compressed) as you near the end of the stroke. As you get near the bottom of the suspension stroke... you're so oversprung that the springs don't allow the tire to conform to the road surface. This could be exaggerated by insufficient rebound damping as well, as well as a bottom-out circuit (don't know off the top of my head whether your forks incorporate one or not).

Once again - conjecture here - but I think the difference in heavy braking vs. medium braking may be one of time, not force. When you really get on the brakes hard at 80... your compression damping is only allowing the forks to compress at a certain rate. Since you're on the brakes hard, you're scrubbing off speed rapidly, so by the time the forks have compressed to a point where they start to lose compliance due to the increasing spring rate (as your forks compress so does the air pocket, which yields a higher total spring rate), you've already slowed to a point where the forces on them aren't problematic). In contrast, during medium braking, where the length of time you're actually on the brakes is extended, the forks might have time to get near bottom while still under a good load. Does this make sense? Do you feel this is what might be happening?

Ideally, I'd say get some heavier springs in there, drop the oil level to a point where it allows you to use most of your suspension stroke without bottoming under the hardest conditions, ace the bottom-out circuit if present, and definitely revalve (your rebound damping is going to suck ass going up in spring rate unless you modify it). Thing is - if you rework your forks without messing with the rear end, at your weight, the bike's going to handle like a pig. So ideally - you're going to want to rework the front & rear.

Take this all with the assumption that there's nothing mechanically wrong with the bike
 

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I believe its your brake pads!

I had the same thing after racing in homestead on the EBC HH that tracks hard on the brakes. I basically blued the rotors and the front end chatter HARD, it felt like ABS brakes kicking in.

This is what I did to fix it! Take off all the pads, I used a DA sander and sanded the pad surface it was glazed. Clean off the metal backing and put stop squeel or sillicone on the metal of the pads. Rotate the pads around, from one caliper to the other. Then sand down the rotors also and give that a shot, and make sure everything is well tight.
 

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Trust me its your brakes! Your forks are fine if they are not leaking. Was the problem there when you bought the bike?

The gsxr 1000 I believe are .90 springs for 170 pound riders. If you still think its forks grab a single ziptie and rap it around the fork to measure fork travel. If the zip tie bottoms out then yes have the forks rebuilt.

Like this:

 

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A new view point from the UK!! Do you only have a problem under braking or does the bike handle strangely in any other ways?? This is very important as if it's suspension related then you should have problems when going round corners! It sounds to me that you have too much compression on, or too much preload on, along with too much compression. I know that you said your 220lb but that isn't that heavy really!!Set your dynamic sag (bike and rider) to about 30mm of travel from topped out(roughly, as this figure can go up or down depending on how you ride). Use the ty-wrap method as mentioned above to get this measurement. Once your sag is set (do front and rear while you're at it) then wind your compression off until the chatter goes away. If it goes away then you need to do a full setup to make the bike handle properly all the time. Don't go spending money until you;re completely sure that you need too. Then gain a proper understanding of how to set your suspension up, and what symptoms dictate you adjust which settings. Hope this helps
 

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I'd bet money it's one or both of your rotors. Do you have a buddy with a gixxer that you could swap wheels or rotors to try out?

If you find out it's the rotors - problem fixed. But to keep it from coming back I'd ditch the EBC's. The best pad out there in my opinion are the Vesrah SRJL-17's. Spendy, but worth it. I've heard the standard RJL's are very good as well, but have not tried them.
 

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I'd bet money it's one or both of your rotors. Do you have a buddy with a gixxer that you could swap wheels or rotors to try out?

If you find out it's the rotors - problem fixed. But to keep it from coming back I'd ditch the EBC's. The best pad out there in my opinion are the Vesrah SRJL-17's. Spendy, but worth it. I've heard the standard RJL's are very good as well, but have not tried them.
I may be wrong, but just getting rid iof the EBC's may not solve the problem...warpped rotors are caused by hot spots, i.e. hard braking before you stop, the rotors heat up where the pads are, especailly HH's...but the rest of the rotor cools off, If before you come to a rest, use the rear brake, and be kight on the front...I had warpped rotors, with EBC's, got new rotors, and followed the above, and never had a problem after that.

Oh, and the other Vesrah pads are the RJL 8's..
 

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Definitely wouldn't be the rotors. If it was the rotors, he'd be feeling a pulsing at the lever, and not the whole front end racheting like it is. Also, light braking would reveal the same symptoms (although less pronounced).

meehan8, I have the same problem with my K4 750. I've had some techs take a look at it and speculate everything from brakes to loose steering head to suspension. My gut instinct is that it is the suspension. I was planning on getting my internals reworked anyway; this just accelerates the need.
 

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It's all guesswork until you eliminate all the possibilities yourself. Most techs know jack about nothing in terms of suspensions, especially at factory shops. Your best bet is to have them reworked by a qualified suspension shop. That way you know for sure they are set right, and put together right, and are set for YOU. If it still does it, then you can go and eliminate the easier things like steering head problems, rotors, etc.

In my troubleshooting of my suspension problems, that it's best to eliminate all the easier possibilities first...which you've partially done. If you know that what you've checked is good...then do the suspension work or learn to do it yourself.
 

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Definitely wouldn't be the rotors. If it was the rotors, he'd be feeling a pulsing at the lever, and not the whole front end racheting like it is. Also, light braking would reveal the same symptoms (although less pronounced).

meehan8, I have the same problem with my K4 750. I've had some techs take a look at it and speculate everything from brakes to loose steering head to suspension. My gut instinct is that it is the suspension. I was planning on getting my internals reworked anyway; this just accelerates the need.
not necessarily....especially w/o steel lines.

I have warped 2 sets of rotors w/ EBC pads and ZERO sets with other pads. EBC are notorious for warping rotors.

Get yourself a dial indicator for like $20 a check the runout. the factory spec is .012in runnout is acceptable.
 

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i had that same problem and almost shelled out for new rotors. ALMOST. lets analyze first. do you do alot of wheelies, especially in 1st gear where engine braking will slam the front end down? that was my problem. the guy i bought my bike from was a wheelie junkie. to many rough landings can cause the front end to loosen up. below is a diagram and i will explain how to remedy the problem:

1. loosen number 8
2. tighten the bottom number 12 (this is where hard landings from wheelies do damage.) you will need to use a mallet and the tool that makes nails flush in hardwood floors. put the tip between the grooves and hit gently. it will tighten.
3. tighten the top number twelve. number eleven is a washer.
4. now re-tighten number 8.

now take her for a spin. if the problem is less noticable now just follow steps 1-4 again and that should be all it takes.
if the problem is gone, then job well done.
if there is no difference, then sorry to say it, but, then it is probably the rotors.

but like i said, i almost wasted $300.00 so it's worth the try.
JUST DON'T FORGET TO RE-TIGHTEN #8!!!
 
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