SOHC.co.uk Forums > CB350/400
Fork Seals
Skoti:
--- Quote from: Oddjob on July 30, 2026, 12:06:06 AM ---I’m trying an experiment with my 550 fork seals. For some reason the space left by Honda is deeper than the fork seals they used. So that meant either a gap above or below the seal and the circlip holding it in place. Didn’t seem right to me so I looked around and found some genuine Honda seals that were the same external and internal size but were wider in depth. Seem to remember it was an off road bike and not imported into the UK so I was forced to source some in the USA. Not tested them yet but they are double lipped as well.
Oh and they come with a spacer as well, so I can fit the standard seals if I want but with a spacer underneath. Seems like a result.
--- End quote ---
Aye,
Same with me, changed mine recently and noticed the gap above the circlip.
According to P.O. It still had the original seals.
Fitted genuine Honda seals but gap still exists.
Strange.
Oddjob:
I’ve checked the parts books Bryan and I cannot spot any changes to the seals. They start off one size and they stay the same size till the model is discontinued. And yet as Skoti says there is a gap between the seal and the retaining clip. That worried me a little, could the seal be moving up and down inside the fork slider? Over time would that become a problem? Why had Honda not fitted a deeper seal or just cut the clip groove just above the seal to stop it moving.
So I started looking at it and I think you’re right, they started saying fit 750 seals instead but they appeared to be the same size, maybe the 550 ones were single lipped and the 750s were double, I managed to source some which I thought might just solve the problem, they are thicker but they also came with a spacer, which made me think why didn’t Honda just fit a spacer in the first place? Then I got sick last year and that was that. Only remembered it yesterday.
I do remember thinking last year, IF I do fit a spacer where is best, below the seal or above. Both positions have merit. My thinking is below is best but maybe I’m wrong. Any thoughts?
McCabe-Thiele (Ted):
I fiiltted the deeper seals on my 500 as sold by Pyramid.
My 400 forks had been rebuilt by the PO, I did not know the 400 had a similar design.
K2-K6:
There's quite a lot of detailed development in MTB forks that could be of interest.
This just one of them https://www.totalbleedsolutions.co.uk/products/skf-dual-fork-seal-kit-fox-air-34mm-fn-mtb-for-mountain-bike-mtbdual34fn?variant=54135620370817&country=GB¤cy=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gad_campaignid=22869149694&gbraid=0AAAAAoPeQzp8BD-xWIRj6jLI41b5-lR1y&gclid=CjwKCAjw7KvTBhA6EiwAWnutYdWoxqC34bAZgie_1IuIx-NxXFLh-yXPBoN0fZrAl9X2QZqRaV_q2xoCUE0QAvD_BwE that gives a view. They ordinarily list the sizes in technical specifications, so finding a match could be possible.
Whether there's equivalent in size (particularly of OD) I've not specifically looked. I work on them in various diameter up to 40mm stanchion size, they cascade downward from there, through 38, 36, 35, 34 etc.
Many use a serviceable foam wiper ring above the seal and under dust cover that catches dust etc.
As I've put on here before, favour Motul fork oil for both lubrication and choice of specific viscosity to match need in getting good response and damping characteristics.
Most of the MTB stanchion are high strength aluminium, with hard anodised coating. Focus on not scratching that, along with low stiction is high on agenda in that field.
K2-K6:
This one give seal comparison in chart
https://www.scribd.com/document/556118464/DimensioniSeals
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