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ratbga56
Settled In Member
United Kingdom
190 Posts |
 Posted - 19/01/2008 : 07:49:30
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does any1 else suffer from wot feels like chatter thou the front forks under heavy braking on track days, iv been told it is due to a design fault with the forks and by puttin new insides in them will sort the problem, is this true? or does any1 know a cheaper way of curing it?  |
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mick41zxr
Familiar Member
308 Posts |
Posted - 20/01/2008 : 23:17:35
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Two problems with the ZXR 400's. The internals are crap, if youy know what you are doing you can use the internals from late model show forks. Some machining required. Also the inner tube hits the fork cap at about 15mm from bottom out, the cap can be machined to allieviate this.
What you are feeling is the forks bottoming out. Cheapest way to fix is to use some stiffer fork springs & play with the air gap forks to conrol bottom out. A base line spring for racing is 0.9kg/mm. Try 120mm air gap & 10 weight oil & go from there. Decent valving & rebound needle set up makes a difference when you are really going for it.
Regards,
MB |
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techie
Regular Member
New Zealand
919 Posts |
Posted - 21/01/2008 : 18:41:40
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| It may also be that your oil height is set too high and you are getting hydraulic locking of the forks.Also you can get chatter (or feels like chatter if the discs are warped. Check them for run-out as it does not require a hell of a lot before you start to feel vibration under brakes. |
Lose weight and go faster. |
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ratbga56
Settled In Member
United Kingdom
190 Posts |
Posted - 21/01/2008 : 21:31:56
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| iv checked the brakes as it was my first thought they are all good, and iv been tlkin to some suspension companies and they said the same as mick i am running 10w oil and it feels work, one bloke said try thinner oil so ill give it a go, when u been air gap do u been the gap between the top of the fork tube and the oil? |
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mick41zxr
Familiar Member
308 Posts |
Posted - 21/01/2008 : 23:00:12
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Take your forks out, caps off & springs out. Compress forks until dust seal is against the bottom castings, Air gap is the height between the top of the inner tube and the oil. Use a cable tie around the lower fork leg assemble forks with spring out. Compress until bottomed out (a hard mechanical bottom out) measure & record the setting. Reassemble forks with springs. When riding at the track you want the (push the cable tie up) you want the forks to bottom out approx 5mm above the hard mechanical bottom. You will still hit the hydraulic stops when you accidently run over a kerb. I personally remove the hydraulic stops & just rely on spring & air gap.
Regards,
MB |
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ratbga56
Settled In Member
United Kingdom
190 Posts |
Posted - 22/01/2008 : 22:56:56
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| cool i run a cable tie at my last lydn hill track day and they sat at bout 5mm from the botom, i will try this softer oil will ur air gap and keep u posted thanks for the help? how do u remove the hydraulic stops? |
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mick41zxr
Familiar Member
308 Posts |
Posted - 23/01/2008 : 00:59:11
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| They are the plastic shrouds held in by circlip on the damper rods. |
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ratbga56
Settled In Member
United Kingdom
190 Posts |
Posted - 23/01/2008 : 22:53:56
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| u just remove them all? is it shown in the manual? |
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mick41zxr
Familiar Member
308 Posts |
Posted - 28/01/2008 : 10:52:09
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Two circlips on each damper rod holds them in place, still suggest some changing internals you really can feel the difference.
Regards,
MB |
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front fork chatter
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