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Front fork seals

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Markru12 View Drop Down
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    Posted: 12 Feb 2020 at 16:37
 v7 1967
The front fork seal are meant to be 35 ID/ 50 OD and about 8/9mm Thick
I have installed as such and have had the leak issues  since fork dimensions are 34,7mm
Does any one have a solution to this problem

Mark Rupert
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 2020 at 18:30
Hmm, that's interesting.On the face of it one might expect the seal ID to be exactly the same as the fork OD. Might it be that the seal being a transition fit compresses slightly taking up the 0.3 mm clearance, I don't know. This is something I haven't experienced, never having had to change the seals on my Loops.Being a Loop zealot I'll be very interested to see what others make of this.
No help to you I'm afraid Mark, sorry.
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c13pep View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 2020 at 21:18
Gutsibits list a fork seal at 34.74 x 47 x 7/9, although not your outside diameter it shows that these may be available at a bearing suppliers to your exact spec

CHRIS
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 2020 at 21:32
Any seal sold for a 35mm shaft diameter will measure less than that ID, otherwise it would never seal.
There is always a spring round the seal lip which holds it tight round the shaft.

Best thing you can do is ask a bearing supplier, tell them the OD of the tube and ask if they have a seal to fit. They will need to know the ID of the fork lower that the seal fits in to.
Brian.

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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 2020 at 23:43
There is another reason, specific to 70s-80s Guzzis with cartridge fork dampers, to avoid aftermarket seals: Guzzi-designed forks are smaller in diameter relative to their nominal sizes than most forks. Other manufacturers make their tubes to the nominal diameter, say 35mm, then bore their sliders to 35mm plus the allotted clearance. Guzzi commonly bores the sliders to size and grinds the tubes smaller (34.6mm) for the needed clearance. What this has to do with seal selection is that aftermarket seals are most likely designed for slightly bigger tubes that those used on most 70s-80s Guzzis. For example, the current Guzzi 35mm seal, which is blue in color and carries the Marzocchi brand name, is marked as 34.74mm.

Richardson, Dave. Guzziology Version 9 (p. 619). Kindle Edition.

The above extracted from Guzziology may explain the apparent anomilies associated with Guzzi fork seals.
Where Loop frame models are concerned the last sentence is of particular interest.
So it appears that you must buy the Guzzi seal,not just a generic example.

Contrary to what I said earlier I must have done this job before because I've found a receipt for fork seals from Guzzibits from 2015.
I can't remember doing it (Oh dear!) but I remember changing the springs so I must have done it then.
So, get your seals from Guzzibits.They are obviously the correct size.
The genuine parts book lists those seals incorrectly as 50x35x10.The b***t*rds !!

Edited by Dave P. - 13 Feb 2020 at 00:14
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1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Markru12 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Markru12 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 2020 at 04:20
Thanks for the input Gents
Will see  what Guzziology says
Perhaps use an imperial size seal.
Or see if one is available
say 2"x 1,5/16 X 3/8
Always a little hitch.

Cheers

Mark
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 2020 at 07:45
Highly unlikely an imperial seal will have the correct OD.
Brian.

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