Fork Rebound Needle Dismantle

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Garry Coates
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Joined: Tue Aug 11, 2020 1:57 am

Fork Rebound Needle Dismantle

Post by Garry Coates »

The Standard Fork Upgrade Service Guide is an excellent starter to understand these forks. Can the fork rebound needle be removed from the core damper tube (preload/rebound)? How does the screw and needle work together?

I may be able to get a better forkcap and damper core from other bikes but I do not know how the needle would then be attached.

Has anybody done this with forkcaps that are aftermarket or from other bikes?

Regards
Garry
1995 Honda ST1100 ABS/TCS
1999 Honda XR600R
2013 Husqvarna TXC310R
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Cadbury64
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Location: Auckland, New Zealand

Re: Fork Rebound Needle Dismantle

Post by Cadbury64 »

The screw and needle are one and the same, and thread through the preload adjuster. I've never tried to remove the needle from the adjuster and assume there must be a circlip in there somewhere to retain it. The assembled cap then screws onto the hollow damper rod so the needle tip ends up just above the rebound valve body; bypass oil flows up the hollow of the damper rod and out through a port in the side , with the needle adjusting the flow.

When you reassemble the fork, you need to set the needle to the right position so the adjuster works correctly; I screw the needle to the full "in" position (or so the screw head is flush with the cap top) then wind the cap assembly onto the rod until the needle just bottom lightly; hold in place there, back off the needle, and tighten the locknut. This means you should be bottoming the needle (i.e. closing the adjuster fully) when the screw is fully "in".

The magic of cartridge forks happens mainly in the design of the valve body and shim stack; the external adjuster just allows you to vary the fixed bleed area. If you felt the maximum bleed area was too small with the needle full retracted, then there is the option of adding another fixed bleed hole through the valve body itself, but in my experience more free bleed area does not help with the feel of control. The reason the ST1100 cartridge was so fluid but loose in action was the large fixed bypass ports, in those valves they are created by small machined channels in the shim sealing faces.
2017 MT-10SP, 2019 Vespa Primavera 150
Garry Coates
Posts: 10
Joined: Tue Aug 11, 2020 1:57 am

Re: Fork Rebound Needle Dismantle

Post by Garry Coates »

Hi Cadbury,
thanks for the feedback. There certainly must be a way to separate the screw from the adjuster pushrod as there forkcaps with the screw but not the pushrod sold aftermarket and secondhand from other bikes. Its one of those things that a spare one would be useful to play with.

I note you have an ST1300. How is that treating you?

Regards
Garry
Last edited by Garry Coates on Sat Oct 02, 2021 1:38 am, edited 2 times in total.
1995 Honda ST1100 ABS/TCS
1999 Honda XR600R
2013 Husqvarna TXC310R
Garry Coates
Posts: 10
Joined: Tue Aug 11, 2020 1:57 am

Re: Fork Rebound Needle Dismantle

Post by Garry Coates »

I have done a little more research on bikes using conventional show 41mm forks.

For instance: Honda NSR250R 1989-1996 has very similar setup. And TYGA does work on them. I have found their Front fork overhaul on a MC28 NSR 250 SE at: http://tyga-performance.com/images/00ps ... ntfork.pdf

Step 4 explains disassembly of the fork cap and removal of the rebound adjuster from the preload.

The question has anybody done this and have they inspected the rebound adjuster and rod? There should be some indication of how they are joined (rivet, press fit, thread etc.)? Some showas have 3 punchmarks in the rebound tube at the end that requires drilling to the adjuster screw inside before separation.

Step 14 pic shows the rebound screw separate from the rod. The rod seems to have a small hole at the end which maybe from drilling the punchmarks.

Regards
Garry
1995 Honda ST1100 ABS/TCS
1999 Honda XR600R
2013 Husqvarna TXC310R
jchesshyre
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Location: Chester, Cheshire

Re: Fork Rebound Needle Dismantle

Post by jchesshyre »

I had an MC16 NSR250R which I'm pretty sure had air assisted forks as standard.
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Cadbury64
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Location: Auckland, New Zealand

Re: Fork Rebound Needle Dismantle

Post by Cadbury64 »

Garry Coates wrote: Tue Aug 18, 2020 10:31 am I have done a little more research on bikes using conventional show 41mm forks.

For instance: Honda NSR250R 1989-1996 has very similar setup. And TYGA does work on them. I have found their Front fork overhaul on a MC28 NSR 250 SE at: http://tyga-performance.com/images/00ps ... ntfork.pdf

Step 4 explains disassembly of the fork cap and removal of the rebound adjuster from the preload.

The question has anybody done this and have they inspected the rebound adjuster and rod? There should be some indication of how they are joined (rivet, press fit, thread etc.)? Some showas have 3 punchmarks in the rebound tube at the end that requires drilling to the adjuster screw inside before separation.

Step 14 pic shows the rebound screw separate from the rod. The rod seems to have a small hole at the end which maybe from drilling the punchmarks.

Regards
Garry
The hole at the top of the damper rod is to allow the oil that passes the needle to exit the damper rod. In the VTR1000, the needle is much longer and reaches down to the rebound piston area. The oil bleed hole for that is in the upper part of the rebound valve threaded shaft.

From Tyga's instructions (which are interesting, thanks for the link), the rebound needle should just screw down and out of the preload adjuster. I've not done that but it sounds logical, when installed you can only screw the needle in until it bottoms in the valve, so the design would only need to stop you from screwing the needle out too far.
2017 MT-10SP, 2019 Vespa Primavera 150
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8541Hawk
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Re: Fork Rebound Needle Dismantle

Post by 8541Hawk »

Cadbury64 wrote: Mon Oct 05, 2020 8:59 pm From Tyga's instructions (which are interesting, thanks for the link), the rebound needle should just screw down and out of the preload adjuster. I've not done that but it sounds logical, when installed you can only screw the needle in until it bottoms in the valve, so the design would only need to stop you from screwing the needle out too far.
It has been a few years since I last removed the needle to regrind the taper, so I can't say exactly but I do know it came out easy and I do believe it just unscrews like stated.
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