Fork Seals

[rjp996 1,091]

Well coming back from Bournemouth to Tunbridge Wells the other night I noticed one of the front fork seals as gone to the extent oil was running down the fork leg.

 

Fortunately, for the next two weeks im working in Asia, so don't need my bike fr the daily commute.

 

My thoughts were to order some seal's for when I return and change them myself. From the sounds of it, it sounds like a relatively straight forward task (undoing fork yoke clamps, slide out, disassemble fork etc) - If anyone has done this before, could they point out any difficulties in the process please.

 

My other question is on fork oil, whats the type that people would recommend for a stock set up like mine (NC750x).

 

If of interest, I will look to take some pictures and post a bit of a how to if anyone would find useful.

 

 

 

Edited March 6, 2017 by rjp996

[wingrider.steve 943]

Before you remove the forks from the yokes it's a good idea to crack loose the bolts that hold the damper assemblies in place (the bolts that go up into the bottom of the fork sliders, the ones you can't get at until you remove the wheel spindle), it's a lot easier to do while the forks are held steady in the yokes & the spring pressure helps to stop the damper assemblies turning as you try and undo the bolts.

Then loosen just the top-yoke pinch bolts and loosen the fork top nuts, again a lot easier before you remove the forks from the bike.

Edited March 6, 2017 by wingrider.steve

[rjp996 1,091]

Thanks for that Steve. Im assuming that if im chnaging the fork seal / oil on one leg I should change the other as a pair ?

[embee 7,288]

Do them as a pair. In my experience if one side leaks the other side may well be not far behind, you'd kick yourself if you end up having to go through the process a second time.

 

As Steve says, remove mudguard, caliper & wheel. Crack the damper retainer bolt (20) in the bottom of the fork leg, slacken the top yoke pinch so it isn't gripping the stanchion, then slacken the top cap while the bottom yoke still grips it. Note that when you then slacken the bottom yoke pinch bolt the leg will drop, so keep hold of it at this stage. It's not usually difficult to prise the dust seal out, then the circlip 14 (DON'T forget to remove this!) and slide the fork apart to knock the oil seal out having removed the bottom bolt completely. The top bearing bush (7) and washer (6) come out with it, these just gets refitted as long as everything else is OK. It's best to have a fitting tool of some sort, a proper one makes it very easy but you can improvise with an old seal and a tube etc. at a push. Make sure you get the seals the right way up. A new sealing washer on the damper retaining bolt (21) is usually recommended, though I have re-used them with no leaks, your choice.

 

There is some preload on the fork spring but not a huge amount, I use a socket on an extension and a T-bar so you can keep pressure on it as you unscrew (and refit).

 

My preferred oil is Fuchs/Silkolene "Maintain" RSF 7.5W for stock front end. See the white table halfway down here http://www.peterverdone.com/archive/lowspeed.htm which lists ACTUAL viscosities and viscosity index (VI), something round 35cSt at 40C and a high VI is about right, that's like the Showa SS8 (I think that's factory fill) and the Silkolene PRO RSF (now called Maintain RSF) 7.5W. Note that the nominal rating (7.5W or 10W etc) doesn't really tell you everything, the actual viscosities are more useful. I've tried low VI oils before now and they get very knobbly when cold, so I'd advise against. Set oil level to a height rather than an amount, the workshop manual will give the correct oil level (spring/spacer out, fork fully compressed and upright).

 

Make sure you refit the washer (4  below) at the correct end of the spacer, between spacer and spring. Also note the topping out spring (9) and the lock-stop piece (11) which will be loose parts when disassembled, and note which way up the main spring is (close coils one end).

 

Plenty of How-to vids on Youtube, well worth reviewing.

 

https://www.bike-parts-honda.com/pieces-honda-detail-71520-71520-NC750XAE-2015-F_09-NC+750+X+ABS.html

Edited March 6, 2017 by embee

[Guest bonekicker]

Richard what great help you have just been given--clever lads--Yes some strip down and reassemble pics would be great--thanks---we just love pic's.

[rjp996 1,091]

guys, thank you very much for this. I ordered a fork seal tool to make life a little easier.

From watching some youtube's it looks like you not only need a tool to seat the new seal, but also to seat the bush that come off when you separate the tubes. Looking around these tools seem less common, and the youtube I saw last night inserted it using a bit of plastic tube on the fork held in place with a u-bolt, so may give this a go. regards

[rjp996 1,091]

one more question (sorry) - looks like there is a big diff in price between Honda and non Honda seals (non Honda look to be 1/3rd of the price of Honda). I was going to get the Honda ones, but through i would ask for experience as there may be good brands out there that are just as good (or even better...).

 

[DMB 1,341]

Richard - Alternatively you could take your bike to John Harris in Crowborough.  They did a good job on my Deauville when the seals went a year or so back.  But I recall that you are the person who changed his chain and sprockets one evening after work, so I would be very surprised if you take any notice of my suggestion!

[rjp996 1,091]

DMB, I had considered taking it up to John Harris, but i work in an industry where i work on some very abstract, non material delivery's (algo's) so don't get to fulfill my desire to a make and do things.... so part of the enjoyment for me is in doing something practical and getting the warm feeling of achievement - when it goes well :-)

Wow that came out a bit deeper than I expected - if I get stuck at least I will be able to almost carry my bike in bits to John Harris :-)

 

[wingrider.steve 943]

1 hour ago, rjp996 said:

one more question (sorry) - looks like there is a big diff in price between Honda and non Honda seals (non Honda look to be 1/3rd of the price of Honda). I was going to get the Honda ones, but through i would ask for experience as there may be good brands out there that are just as good (or even better...).

 

I'd go with genuine Honda, at least you're dealing with a known quality and while changing fork seals isn't a difficult job you don't want do be doing it twice if you have problems with aftermarket seals.

[Trumpet 215]

Genuine Honda seals have a spring tensioner on BOTH sides of the seal, Cheaper seals do not. They will typically will last longer than a third party seal so would be worth the extra. I'd also replace the dust seals whilst you are at it. The new seals should be greased with fork specific grease as well. You can buy stainless steel clips as well to hold the seal in. The original clips do rust under the dust seal. And remember, they need go in a certain way round, otherwise they just leak right away (from personal experience) .  I have a selection of plastic pipes used for drifting in seals and bushes. 

Edited March 7, 2017 by Trumpet

[michael 324]

On 7 March, 2017 at 02:10, rjp996 said:

one more question (sorry) - looks like there is a big diff in price between Honda and non Honda seals (non Honda look to be 1/3rd of the price of Honda). I was going to get the Honda ones, but through i would ask for experience as there may be good brands out there that are just as good (or even better...).

 

My personal experience went like this:

Bought after market seals from a well known brand. Installed* the seals only to find they were so tight they actually locked the suspension. I called a friend of mine (an American moto-journalist) whom admonished, "michael. always, always, always buy factory oil seals.  the tolerances are much better than any aftermarket units."

 

So I ended up buying 2 sets. The aftermarkets and the "gulp priced," Honda Parts.  The Honda parts were easier to install and worked like a charm.

 

* Install. The only issue I had was during the removal of the internals. The allen head bolt that's accessed from the axle hole requires a loooong head allen head socket.  My tool box didn't have any so a trip to the tool shop solved that.  My other rookie mistake.

 

I took a couple of hours for the in and out, and like my friend says, felt immediately impressed with my accomplishment afterwards. Wouldn't hesitate to do it again.

[rjp996 1,091]

Thanks for all the help on this - i finally got the seals installed last weekend - unfortunately I had a number of issues and had to rope my wife in to help so no pictures.... My experience however is :

 

getting the forks out was easy - one tip was I needed to use a low profile 6mm hex socket and my smallest toque wrench to do back up due to the space issue on the top fork holder.

Separating the tubes - one separated relevantly ok, however the other was pig..., due to the bearing ring not wanting to budget inside. by pulling the forks apart it pulls the slider bush against the 'other bush to un seat it. The side that was stuck took so much force that it destroyed the teflon coating on both bearings and had to replace them (~£20) and a weeks wait.

Second issue was the oil. I bought Repsol 10w fork oil for no other reason that I could get hold of it next day on amazon.

I used a fork oil tool to get the 104mm height and found that it used 1.1ltr and I only bought 1l, so another couple days wait for more oil.... I think it may.. have just worked with 1litre but a split a very Small amount.

 

all went back together simply - have ridden 500 miles this week and im glad to say oil seals are holding fine. If I was doing it again I could prob do it in 2 hrs end to end.

 

Tools i 'invented in' - I love tools ;-) a seal installer, fork oil depth tool and a ultr low profile set of hex sockets, and some very long hex key sockets for the bottom bolt that holds the internals in place.... :-)

Now I have a few more tools im on the lookout for a second tool box :-)

[Rednc750se 171]

Well done Richard, more experience for you and saved a few £s as well. And most important the satisfaction of doing the job.

[akstsstjs 30]

On 07/03/2017 at 12:20, Trumpet said:

Genuine Honda seals have a spring tensioner on BOTH sides of the seal, Cheaper seals do not. They will typically will last longer than a third party seal so would be worth the extra. I'd also replace the dust seals whilst you are at it. The new seals should be greased with fork specific grease as well. You can buy stainless steel clips as well to hold the seal in. The original clips do rust under the dust seal. And remember, they need go in a certain way round, otherwise they just leak right away (from personal experience) .  I have a selection of plastic pipes used for drifting in seals and bushes. 

PM sent

[kevcl15 45]

Hi Richard,

 

Had a leaking seal on mine so just stripped them down, gonna give them a good clean and either a coat of paint and lacquer or powdercoating to get them looking good again.

 

One question I do have is the measure of the oil. Is the 104mm measured with the stanchion all the way out of the fork lower or all the way in?? I'm assuming it's all the way out, but think it's worth checking!!! :-)

 

Cheers.

 

Kev 

[embee 7,288]

Fork oil levels are stated as measured from the top of the stanchion with the spring, washer and spacer removed, and the fork fully compressed and upright.

[kevcl15 45]

4 minutes ago, embee said:

Fork oil levels are stated as measured from the top of the stanchion with the spring, washer and spacer removed, and the fork fully compressed and upright.

Hi,

Thanks for that Murray, think if I'd gone with what I was thinking then there'd have been oil everywhere!!! 

 

Cheers.

[trisaki 2,029]

On my X I've tried  140mm air gap instead of the 104mm that Honda say  , as I've always  found the forks very choppy  , now with 140 I am very happy  

[embee 7,288]

I'm using 140mm too, though I have emulators fitted so not really a true comparison. You can always try it at 140mm and if you find the suspension travelling too far then add a bit more, the oil level mainly influences how the air spring effect comes into play and stiffens the effective rate as the suspension reaches full compression, the higher the oil level the faster the effective rate rises (less air gap so rapid pressure rise)..

[Black15 66]

Hi. Does anyone know what size/type of spanner is required to remove the low profile aluminium hex fork caps on the 2017 nc750X?

 

[leejbarker82 0]

Hi,

 

Any idea what to do when the 2 bushing seals don't want to come out and are stuck on the lower part housing meaning I can't separate the 2 parts.

[wingrider.steve 943]

I take it you have removed the circlip above the seals and the damper bolt in the bottom of the forks?

[leejbarker82 0]

47 minutes ago, wingrider.steve said:

I take it you have removed the circlip above the seals and the damper bolt in the bottom of the forks?

Yes both removed... And the seal is out. Just the bushing won't shift

[wingrider.steve 943]

Try bolting the fork back into the yokes so it is held firm then you can quickly slide the fork lower tube quickly & firmly up and down repeatedly and you should be able to separate the fork.

You can be a bit brutal when doing this, you won't hurt anything!