Weird Stiction Problem

C

Chili

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Apr 9, 2002

8,062

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• May 31, 2005

• #1

One of my son's racing buddies is having a nightmare time with his 04 RMZ-250. I figured I'd prod some of the experts here to see if I can come up with something to help him as the kid is ready to quit racing because this bike is treating him so bad.

The rider is a 123 lb. MX'er not an expert but an accomplished racer with several years experience on 80's before this bike. The bike suffered from severe headshake from day 1, his Dad has had the suspension revalved twice now, sprung appropriately (forgot to ask him the spring rates) and the bike is still trying to kill this kid. The last detail that likely leads us to the problem is fork sticition or binding. With the forks off the bike they are soft as can be and move fluidly, put them on the bike and they barely budge if you grab the front brake and try to compress the forks. Near as I can tell Dad is putting everything together correctly and not over tightening the pinch bolts. It has to be something tweaked or something in the assembly process causing this problem since the forks move well when off the bike. Any ideas where to start?

 

O

overbore

Member

Dec 24, 2001

362

0

• Jun 1, 2005

• #2

loosen the pinch bolts that hold the front axle and have someone push down on the
forks while tightening back up to make sure there not binding from out of alianment
of the axle thru the forks.
overbore.

 

R

russ17

Member

Aug 27, 2002

301

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• Jun 1, 2005

• #3

It seems that all of the RMZ KFX 250 present this problem. I have tried Forkslyck wiched helped a bit. When I push down on the pegs the back will go down and the fronts don't. I don't like it this. I have had no problems with any of the other bikes but these. I have checked bushings, front end alignment ect.
Last time I was in there I did notice that the holes at the top of the inner tube were smaller in size compared to the YZ 48mm forks, also the Seal back up washer is not notched like the YZ either so I am wondering if this is a lubracation problem.

As mentioned above, off the bike the forks feel great ,once bolted to the bike its a different ball game and makes you wonder.
Also the seals on these have a double band I will be taking one off .
Maybe Mop or Wilkey can chime in on this issue.

 

Last edited: Jun 1, 2005

marcusgunby

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Jan 9, 2000

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• Jun 1, 2005

• #4

I wonder if the 05 kx 125 suffers the same as it has the same fork i think? not the new kyb?

My rmz is noticable sticky-however headhsake should be addressed by other means, i would set 105mm of sag, and also run the forks flush with the clamps-the rmz is a tight turning bike and will shake at the std settings.

 

C

Chili

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Apr 9, 2002

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• Jun 1, 2005

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• #5

This is an 04 so I don't think it's the new KYB's.

 

M

Miedosoracing

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Feb 22, 2005

79

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• Jun 1, 2005

• #6

I don't know if this will help, but I do this routine when putting on my forks. I put the bolt through the wheel and forks. Air ratchet the nut down. Tighten the nut/brake side, and go over to the free side. Now it is moveable over the bolt. It can go in and out fairly easy. So I take a hammer and kinda clink on the bottom of the fork. It moves to where it is not being pushed on either side. Don't hit on outside or inside, right on the bottom. If you are trying to match up the bolt with the fork leg, that may not be the best place. I let the fork make the decision of where it should be. Good luck

 

marcusgunby

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Jan 9, 2000

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• Jun 1, 2005

• #7

Yes tried that a few different ways-no difference to stiction, i think its the bush's or seals -i remember the ktm fork used to suffer with stiction until they went to a different bush.

 

steve125

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Oct 19, 2000

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• Jun 1, 2005

• #8

The 05's were supposed to get seals with less stiction. My old 04 KXF 250 had terrible seal stiction. Those forks would have been a prime candidate for the Mobil 1 in the outers if that was possible.

 

Pete Payne

MX-Tech Suspension Agent

Nov 3, 2000

933

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• Jun 1, 2005

• #9

Did you ever think that it just might be bad rider posistioning on the bike. I have seen well seasoned riders fight with this same situation. But normaly it is too much preload /too little sag on the rear spring compounded by too soft fork springs.

 

Pete Payne

MX-Tech Suspension Agent

Nov 3, 2000

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• Jun 1, 2005

• #10

if foreslik realy does relieve that much friction , it would make headshake worse .

 

M

Miedosoracing

Member

Feb 22, 2005

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• Jun 1, 2005

• #11

Well if there is so much stiction, it means there basically isn't gonna be rebound at all when you hit braking bumps. It will keep on packing down lower and lower in the travel, and cause headshake.

 

ellandoh

dismount art student

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Aug 29, 2004

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• Jun 1, 2005

• #12

somebody please put headshake in the motospeak glossary

 

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Rcannon

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Nov 17, 2001

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• Jun 1, 2005

• #13

I still think forslyk is going to help a bunch. I doubt your going to find a more inexpensive way to deal with the issue. If your anywhere near Utah we can use some of mine.

 

C

Chili

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Apr 9, 2002

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• Jun 1, 2005

• Thread starter
• #14

I bought some forslyk that I'll donate a treatment to the cause for this kid. As for the bad rider positioning I had thought perhaps since this was the kids first big bike maybe he was just expecting it to handle like his 80 so we had him spin a bunch of laps on my son's 05 RM125. He looked like he'd never missed a beat out there and his lap times dropped several seconds a lap compared to his bike. Thanks for all the thoughts and I'm open to anymore. Any of the guys that do suspension for a living deal with a similar problem and have any thoughts? Jer? Terry?

 

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russ17

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Aug 27, 2002

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• Jun 2, 2005

• #15

My issues was with the stiction only! the ability to get the front and rear to go evenly when pushing on the pegs. I had a good discussion with Wilkey on this, he brought up a good point and it makes sense to me now. I haven't mapped out the linkage on these bikes, but it seems that they are very slow at the beginning.This effectively allows the bike to squat and feel soft with the initial compliancy, so naturally the rear will go down before the front when pushing on the pegs.
As far as the handling of the bike there was no issues of head shake ect.

 

steve125

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Oct 19, 2000

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• Jun 2, 2005

• #16

Chili, try some Mobil 1 ATF I'll bet that will help with any internal / seal stiction.

 

Pete Payne

MX-Tech Suspension Agent

Nov 3, 2000

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• Jun 2, 2005

• #17

I do it for a living , but hay , Maybe I do not count

 

MXSparx

Mr. Meltsomeglass

Jul 25, 1999

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NoVa

• Jun 2, 2005

• #18

Air Chunk said:

I do it for a living , but hay , Maybe I do not count

Click to expand...

:nener:

 

C

Chili

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Apr 9, 2002

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• Jun 2, 2005

• Thread starter
• #19

Air Chunk said:

I do it for a living , but hay , Maybe I do not count

Click to expand...

Certainly wasn't meant in that way, I appreciate all feedback. I don't spend much time in the Suspension forum and the two experts I knew were in here were the two I mentioned, no slight intended.

 

Pete Payne

MX-Tech Suspension Agent

Nov 3, 2000

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• Jun 2, 2005

• #20

Cool deal , Just trying to help out.

 

P

PMK

Member

Feb 20, 2002

33

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• Jun 5, 2005

• #21

A mild long shot, with the bike on the stand and front wheel removed, do the tubes slide freely thru the clamps? If the triple clamps are not machined accurately with all tube bores and stem bores on alignment it will bind regardless of how you properly align the front end.

Maybe before removing the wheel, just loosen the lower triple clamp tube pinch bolts and see if it frees up. Just a thought.

PK

 

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shockdoc

Member

May 3, 2001

327

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• Jun 6, 2005

• #22

This problem has been worse it seems on the bladder fork KYB's. A temp fix was to slide the fork all away apart (with just the dust seal pryed up) with the spring out to where you could work some good seal grease into the dry seal. Seemed like it would start getting sticky again after a few rides tho.

I have pretty much fixed this problem by first disabling the bladder (which they all need anyways IMO) then installing Synergy fork seals. No where near the stiction as OEM. You may even want to replace the fork bushings. Once the forks have been slammed apart the bushings can be damaged even if they look good.

doc

 

C

Chili

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Apr 9, 2002

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• Jun 6, 2005

• Thread starter
• #23

Thanks for the tips, I'm forwarding this thread on to the boy's father so that they hopefully can get this thing setup.