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1970 Shuttle Fork Plastic Sleeve #748534
09/09/18 7:04 pm
09/09/18 7:04 pm
Joined: Jul 2018
Posts: 146
London, UK
Ianbuck Offline OP

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Ianbuck  Offline OP

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Joined: Jul 2018
Posts: 146
London, UK
What is the function of the plastic sleeve between the bearings, is it just a spacer to limit topping out, or does it also assist the damping function ?

I just read in a post they should remain up by the top bearing.

While rebuilding my forks the replacement plastic sleeves I bought were just too tight to fit in the sliders, so I refitted the originals. The original plastic sleeves are probably a loose fit and will most likely move up and down in the slider, and will at times be down by the bottom bearing.

Where they should be ? An interferance fit by the top bearing or a floating fit?

Ian

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Re: 1970 Shuttle Fork Plastic Sleeve [Re: Ianbuck] #748538
09/09/18 7:42 pm
09/09/18 7:42 pm
Joined: Dec 2009
Posts: 256
Michigan, USA
H
henryanthony Online content
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henryanthony  Online Content
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Joined: Dec 2009
Posts: 256
Michigan, USA
This thread with comments by John Healey should answer your questions. Plastic Sleeve Discussion

I recall driving mine into the lower leg with a length of PVC pipe. Can't remember the diameter. I learned about in a thread on the Triumphrat.net site. Snakeoil's 1966 T120R restoration thread. Maybe you can find it. It is a very good reference.

Re: 1970 Shuttle Fork Plastic Sleeve [Re: Ianbuck] #748552
09/09/18 9:50 pm
09/09/18 9:50 pm
Joined: Dec 2004
Posts: 9,884
Scotland
kommando Offline
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kommando  Offline
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Scotland
Loctite them so they stay up, if they drop your forks will overdamp.

Re: 1970 Shuttle Fork Plastic Sleeve [Re: Ianbuck] #748597
09/10/18 8:35 am
09/10/18 8:35 am
Joined: Jul 2018
Posts: 146
London, UK
Ianbuck Offline OP

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Ianbuck  Offline OP

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Joined: Jul 2018
Posts: 146
London, UK
So the plastic sleeve is just a spacer to control the limit of slider extension. It also assists in creating a bit of a hydraulic buffer on full extension.

It needs to be held in place at the top of the slider tube so that it does not interfere with the operation of the shuttle valve, in particular interfering with the compression valve holes in the stanchion.

Just got to now take my newly installed forks apart and replace the old plastic sleeves 😭😠

Ian

Re: 1970 Shuttle Fork Plastic Sleeve [Re: Ianbuck] #748607
09/10/18 10:45 am
09/10/18 10:45 am
Joined: Jul 2018
Posts: 146
London, UK
Ianbuck Offline OP

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Ianbuck  Offline OP

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Joined: Jul 2018
Posts: 146
London, UK
Further to my post above I spoke to the guys at SRM who say the plastic sleeve needs to float on the stanchion inside the slider ???

The thing that prompted my initial post was the mixed advice there is out there on the fit of these plastic sleeves.

I wish I had a systematic diagram of the fork operation.

Ian

Re: 1970 Shuttle Fork Plastic Sleeve [Re: Ianbuck] #748614
09/10/18 12:38 pm
09/10/18 12:38 pm
Joined: Aug 2001
Posts: 4,521
argyll. scotland, uk
gavin eisler Offline
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gavin eisler  Offline
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Posts: 4,521
argyll. scotland, uk
The 1970 factory manual is pretty vague
"Replace the lower fork bush and damper shuttle at lower end of the stanchion, and make sure the circlip is located correctly on the shuttle. Tighten the special nut."

The drawing is un annotated, not much help there, I needed a magnifying glass to see the tighter ID at the bottom of the sleeve bush that kommando mentions.

kommando knows his forks very well,
SRM "Further to my post above I spoke to the guys at SRM who say the plastic sleeve needs to float on the stanchion inside the slider ???"
Same way of putting it , the sleeve is fixed to the top of the slider, the stanchion runs through it freely.

looking at the drawing , its not clear what the sleeve locates on or if the sleeve was designed to move, but , this was the first year of these forks, and maybe all the faults wern't ironed out. The plain OD and double diameter ID , suggests the OD was meant to be fixed.

if the book drawing showed the forks in max and min extensions things might be a little easier to understand, to me it looks like the minor OD of the plastic sleeve will cover a port in the stanchion on max extension if the sleeve is fixed to the top of the slider. presumably a top out damping. Do what John ( kommando)says.


Last edited by gavin eisler; 09/10/18 12:51 pm.

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Re: 1970 Shuttle Fork Plastic Sleeve [Re: Ianbuck] #748624
09/10/18 3:05 pm
09/10/18 3:05 pm
Joined: Jul 2018
Posts: 146
London, UK
Ianbuck Offline OP

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Ianbuck  Offline OP

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Joined: Jul 2018
Posts: 146
London, UK
You are correct the smaller diameter inside section of the plastic sleeve does cover the ports on the stanchion. But if the sleeve is fixed at the top of the slider this would only happen over a very small range of movement and only on full extension, at which time the stanchion ports are also closed by the shuttle valve as it is working in rebound mode.

I expect there will be some oil trapped above the bottom bush on full fork extension and the sleeve will offer some resistance against this oil.

My initial thoughts on the plastic sleeve operation were; it floated and acted in unison with the shuttle valve, moving away from the stanchion ports on compression, and covering them on rebound.

But I can also see that it is there simply to limit total fork movement on full extension, and act as an oil restrictor to limit pressure on the top bush and oil seal on full extension.

It would be great to be able to see the original engineeting rational behind the sleeve. As you say with a diagram of the fork in a neutral operating position.

I certainly dont want over damped forks, particularly on rebound.

Ian


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