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kramdra
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Joined: 28 Oct 2010
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PostPosted: 14:11 - 28 May 2020    Post subject: Fork oil Reply with quote
I will be rebuilding my forks again with new genuine seals and bushes. I want maximum seal life with minimum maintence and do not care much if the handling is worse, as that is often more fun.

It seems to me that not all fork oil is the same, just like seals. I have tried several 10w oils without any noticable difference in handling, but some do appear to leak easier.

Some list a seal swell additive and others claim the lowest friction. My opinion is that seals require some friction to seal and mechanically wipe the oil from the tubes. Ive confirmed this by adding grease to old seals, the added friction wipes the tube clean, but it is a temporary measure, so I will avoid the low friction products.
My current seals also claimed 50% less friction, and as expected, that means they are shit

What brand oil to get, and what difference can I expect from a 15w or 20w oil?

Will this do what I want?
www.ebay.co.uk/itm/High-Performance-15W-15wt-Motorcycle-Fork-Oil-Suspension-Fluid-1-litre-1L/302462907923
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 14:36 - 28 May 2020    Post subject: Reply with quote
Halfords do a multigrade fork oil. I moved onto it after experiencing severe daming loss on prolonged rides on very bumpy roads due to it getting super hot.

Seems to work well enough in my VFR750.

https://www.halfords.com/motoring/motorcycling/oils/halfords-motorcycle-fork-oil-5w30-1l-724393.html

Some people also use ATF which is roughly 5wt.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Riejufixing
World Chat Champion



Joined: 24 Jun 2018
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PostPosted: 14:46 - 28 May 2020    Post subject: Re: Fork oil Reply with quote
kramdra wrote:
I will be rebuilding my forks again with new genuine seals and bushes. I want maximum seal life with minimum maintence and do not care much if the handling is worse, as that is often more fun.

It seems to me that not all fork oil is the same, just like seals. I have tried several 10w oils without any noticable difference in handling, but some do appear to leak easier.

Some list a seal swell additive and others claim the lowest friction. My opinion is that seals require some friction to seal and mechanically wipe the oil from the tubes. Ive confirmed this by adding grease to old seals, the added friction wipes the tube clean, but it is a temporary measure, so I will avoid the low friction products.
My current seals also claimed 50% less friction, and as expected, that means they are shit

What brand oil to get, and what difference can I expect from a 15w or 20w oil?

Will this do what I want?
www.ebay.co.uk/itm/High-Performance-15W-15wt-Motorcycle-Fork-Oil-Suspension-Fluid-1-litre-1L/302462907923

£7.50 delivered if you order it from their website. Edit: £8.99 via eBay! .. Good ol' ebay.

I would not touch anything that makes the ride more "exciting" or that swells oil seals (?).

You don't want friction on oil seals, the oil film on the stanchions is there partly because you can't get it all wiped off by the seal's wiper, and partly so your oil seal does not wear out. If the seal's worn out, wrong, or damaged through wear or fitting, you may get seepage.

If you put more viscous oil in, the suspension will have more damping which may or may not be a good thing.

Last edited by Riejufixing on 08:10 - 29 May 2020; edited 2 times in total
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Riejufixing
World Chat Champion



Joined: 24 Jun 2018
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PostPosted: 14:50 - 28 May 2020    Post subject: Reply with quote
For oil examples: https://www.sportsbikeshop.co.uk/motorcycle_parts/content_search?s=%22fork+oil%22
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Hong Kong Phooey
World Chat Champion



Joined: 30 Apr 2016
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PostPosted: 19:30 - 28 May 2020    Post subject: Reply with quote
Honda SS8 fluid is recommended, it's 10W.

Only buy OEM seals, I've learned the hard way.
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jeffyjeff
World Chat Champion



Joined: 02 May 2020
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PostPosted: 21:05 - 28 May 2020    Post subject: Reply with quote
I have been satisfied with Motul 15W fork oil.
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blurredman
World Chat Champion



Joined: 18 Sep 2010
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PostPosted: 06:47 - 29 May 2020    Post subject: Reply with quote
ATF for me..
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Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 51k.
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Confusion
Scooby Slapper



Joined: 02 May 2013
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PostPosted: 07:47 - 29 May 2020    Post subject: Re: Fork oil Reply with quote
kramdra wrote:
I will be rebuilding my forks again with new genuine seals and bushes. I want maximum seal life with minimum maintence and do not care much if the handling is worse, as that is often more fun.


Your should get years out of a set of fork seals. Provided the
bushes and stanchions are ok, your seals should last as long
as the factory originals..

Quote:
It seems to me that not all fork oil is the same, just like seals.


I use Athena branded seals. These are made in Japan by KYB/NOK
and are of OEM quality. My current set was fitted in 2013 and have
done 41,000 miles so far. I used Motul 15W fork oil because that is
what the local shop sells.
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Riejufixing
World Chat Champion



Joined: 24 Jun 2018
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PostPosted: 08:14 - 29 May 2020    Post subject: Re: Fork oil Reply with quote
Confusion wrote:
Your should get years out of a set of fork seals. Provided the
bushes and stanchions are ok, your seals should last as long
as the factory originals.

The factory originals are made by someone else, and bought in by the factory.
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Pigeon
World Chat Champion



Joined: 27 Sep 2012
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PostPosted: 01:29 - 30 May 2020    Post subject: Reply with quote
stinkwheel wrote:

Some people also use ATF which is roughly 5wt.


+1 ATF


Dexron 6 ATF fully synthetic (£25 for 5L)
30 cSt @ 40c between a 5w and 7.5w
6 cSt@100

Have also used 0w20 engine oil.....very "comfy", but harder to lean bike.
46 cSt @ 40c
6.8 cSt @100c

Have also used Motul Expert, Castrol and Silkolene 2.5w to 20w in a few bikes

Fully synth ATF is about my happy place. Slightly less crashy than 5w, but doesnt slow the steering like 10-15w
A decent compromise.

But largely depends on spring weight and OEM specs.


I did notice that some oils claim to meet ISO standards for hydraulic fluid. And am tempted to try ISO VG32 as its also 32cst@40 and 5.5 cst@100
Very close to matching ATF fully synth but half the price (£16 for 5L)
Have not tried it though.

Done 50k miles on ATF and engine oil. Not had a seal go bad yet.


Kayaba KHL15-10 = Kayaba 01 = 15 cst@40
Kayaba G10s = 37
Kayaba G15s = 55

Showa SS19 = 14
Showa SS05 = 16
Honda / SHOWA SS-7 16.6
Honda / SHOWA SS-8 36.8

Silkolene RSF 2.5w = 13.6
Castrol 10w = 15
Motul Factory 2.5w = 16
Motul Expert 5w = 18
Motul Expert 7.5w = 22
Silkolene RSF 5w = 24
Castrol Fully Synth 5w = 28
Silkolene RSF 7.5w = 35
Motul Expert 10w = 36
Silkolene RSF 10w = 47
Motul Expert 15w = 57
Silkolene RSF 15w = 93
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