Change the Fork Seals on a GSX1400

[gsxbarmy]

HOW TO Change the Fork Seals on a GSX1400

NOTE: This thread is also available to download as a PDF file from the Downloads (General) Section

From reading the manual, many owners think this quite complex and beyond their capabilities but really it’s very straight forward.
In reading through this article, any quantities of oil for oil/air gap referred to are for standard springs. If you have fitted after-market springs like linear or progressive, use the oil/air gap advised with those springs. Note also that if progressive/linear springs have been fitted, then typically the plastic spacers I refer to below will have been removed also.
1. Get bike setup on Paddock Stand and Headstock stand
2. Remove calipers, front wheel and mudguard
3. Loosen off the two top yoke pinch bolts
4. Loosen off the nut on top of each fork (do not remove!)
You now can work on each fork at a time - so repeat these instructions for each fork leg
5. Loosen the pinch bolts on the bottom yoke of the fork you wish to remove and put and old cushion / blanket, bit of foam rubber etc. underneath where the fork will (almost) touch the ground when removed
6. Wiggle and twist the fork stanchion and slide it out of the yokes. You'll find it gets very close to the floor (hence the cushion etc. above to stop scratching it or banging it on the ground)
OK, the fork stanchion is now out of the bike and we can start on disassembly
7. Holding the top of the stanchion, undo the top nut that you loosened at #4 above. Once it is undone lift it straight up gently. You will see attached to the large nut a rod with a small locking nut underneath. Undo this locking nut and unscrew the rod from the large top nut.
8. Gently pull the small rod out of the fork leg and place to one side
9. Now compress the fork stanchion into the fork lower and pull out the spring and other bits attached to it (there will be a large plastic spacer. Note the order of assembly and which way up the spring is as you remove them (there may be a tapered end on the spring which needs to go back the same upon re-assembly)
10. Get a flat bladed screw driver and gently prise out the fork dust seal from the top of the slider.
11. Once removed, inside you will see a large clip on tgop of the fork oil seal. Using some needle pliers, remove that clip
12. Now get a bowl and turn the fork leg upside down and leave for about 5-10 minutes for all the old oil to drain out.
13. Once drained, get the appropriate fork tool for your 14 and insert down the top if the stanchion. You'll find it lock onto the fork inners.
14. Now get a long allen key and from the bottom of the fork slider, locate the allen bolt in the bottom of the slider. Getting a mate to hold the fork tool, undo the allen bolt. Can be tight!
Sometime here is you don't have a fork tool you can get away without it by a sharp trap on the allen key, or by using an air gun to undo the bottom bolt
15. Once the bolt is undone, get a good grip of the stanchion and the slider and pull them violently in opposite directions. After a few pulls the old oil seal will come out and you will have two pieces of fork in your hand. Note which way the old oil seal fits on the fork leg before taking it off and throwing it away.
16. Get some 1600/2000 grade wet and dry and where the fork slider generally moves (the area normally between the top of the slider and where the fork leg bolts up at the bottom yoke) rub over with wet and dry (wet) - this glaze busts the old rubber build up from old seals and will make the new ones last longer.
Dis-assembly complete!
17. Insert the stanchion back into the fork slider, insert the bolt in the bottom of the fork slider and using the fork tool and allen key (as in #14 above) do the allen bolt up.
18. Slide the new fork seal down (check it is the right way up (as noted at #15) and get it to engage on top of the slider.
19. Now - if you have a fork seal tool, now is the time to use it to hammer the seal in. If not, you can make your own insertion tool from some scrap 41mm waste pipe - just make sure it is long enough to extend past the top of the fork. If using this approach, slide the OLD fork seal on top of the new fork seal, then the 41mm pipe and using a rubber mallet hammer down until the (new) fork seal is seated. Then remove the old fork seal (it will easily prise up). That way you don't damage the new fork seal 
20. Re-affix the large clip you removed at #11 - there is a slot in the inside top of the slider it inserts into.
21. Refit the dust seal - this can be tapped in with a rubber mallet
22. Now holding the fork leg upright, depress the stanchion inside the slider (it probably already is anyway) and fill the fork leg up with fresh fork oil until the level of the oil is 108mm from the top of the stanchion (you can measure this by getting a plastic straw and marking it appropriately, holding it down inside the fork leg from the top).
NOTE: If using after-market springs, use the recommended “weight” oil and set the oil/air gap as recommended by the supplier. For standard springs, use 5w fork oil and set the oil/air gap to 108mm
23. Now, keeping the fork leg upright, and holding the slider, pump the stanchion up and down a few times - this gets rid of air in the inner fork. You’ll know when its full as the air bubbles will stop. Once you have done this, leave the fork leg upright for about 5 mins or so for the oil to settle and then re-check the oil/air gap is 108mm from the top of the stanchion (with the stanchion compressed into the fork leg). Adjust as necessary.
24. Now the oil is in, pull the stanchion out from the slider, and re-insert the fork spring and plastic spacer
25. Now get hold of the rod (removed at #8). From the end of the rod set the gap to the top of the small locking nut to 11mm. Once set insert the rod into the stanchion and keep hold of the top.
26. Screw the large nut from the top of the fork onto the rod so it just locates on the top of the nut (which we set the gap of at #25). Nip this locking nut up on the rod.
27. Placing a pad on the floor, and keeping the stanchion upright, screw the top nut into the stanchion. The springs will push back a bit, so you need to be firm in doing this. Once the large nut is located, screw it down into the stanchion but don't tighten it up quite yet.
28. Now insert the re-assembled leg into the bottom yoke and wiggling it again, push it upwards through the top yoke, so the top of the fork stanchion is level with the top of the top yoke.
29. Torque up the 2 pinch bolts in the lower yoke
30. Torque up the big nut on top of the fork stanchion.
31. Torque up the pinch bolt in the top yoke.
Assembly of Fork Leg Complete! Now repeat steps 5 through 31 for the other fork leg. Note in total you will use about 1.2L of fork oil for both legs. The oil/air gap is a better way of adjusting fork oil, as it allows for any discrepancies in manufacture of the fork leg itself.
32. Once both legs are done, re-assemble the mudguard, front wheel and calipers - not forgetting to pump your front brake a couple of times once the calipers are refitted - and just double check that all bolts are correctly torqued
That's it - job done! For someone who hasn't done it before, job should take about an hour or so to do.
As I say sounds complicated, but really isn't....and the fork tool if you need it you can make yourself if needs be (note they are different for K2-K4 and K5-K7)

Fork oil:
•   5W Fork oil recommended with  standard springs
•   10W Fork oil typically used with aftermarket progressive / linear springs

Oil/Air Gap:
•   Standard springs: 108mm
•   Hagon progressive: K2-K4: 150mm,  K5-K8: 160mm
•   Ohlins progessive: K5-K8: 140mm
        Wilbers progressive: K2-K4: 150mm,  K5-K8: 160mm

[Jay]

Very helpful indeed....Thanks

[rollerfish01]

Thanks Gsxbarmy for a very detail notes. 

There was also a youtube video uploaded by a Japanese owner may show some process for reference:
https://www.youtube.com/watch?v=3RJJGPJfOGA

however I have no knowledge to verify is it showing the correct / full process...

[gsxbarmy]

Its incomplete - just looked at the first part where he is taking the stanchions apart and "pulling out" the oil seal - unfortunately he seems to have completely missed the bit where you have to lock the inner chambers and undo the bolt through the bottom of the slider to be able to do that.

[froudy]

Which if you haven't got the proper tool is the hardest part of the whole job!!

[gsxbarmy]

Which if you haven't got the proper tool is the hardest part of the whole job!!

Absolutely!!!!!! 

[Buddynq]

I am about to attempt my first fork oil/seal change and was chatting with a hydraulics expert who we use through work. I had mentioned the forum etc and the precise measurements for oil level. Barmy suggested using a straw but ol mate said he uses a horse syringe cut to length to draw excess oil out. I thought it was an innovative idea to share

[gsxbarmy]

Yep - top idea!!!

[Hooli]

While you're in there it's worth checking the bushes for wear. Replacing them on a bike with a few* miles on makes it ride like new again.




* I did mine at 108k, but judging by the difference they were worn enough to change by 50k.

[Buddynq]

While you're in there it's worth checking the bushes for wear. Replacing them on a bike with a few* miles on makes it ride like new again.




* I did mine at 108k, but judging by the difference they were worn enough to change by 50k.

OK - I'm about to tick over 105k so will look into that.
What is the 'magic' fork tool?

[KiwiCol]

I think Hoolis' distance will be miles, yours will be 105km wouldn't it?

[Buddynq]

Yes - A good observation

[Hooli]

I suspect they need doing at 100k in km too, the difference I noticed in mine was the shake when cornering etc that I'd noticed since about your mileage went.

The magic tool is a pipe with the end cut to shape to lock the cartridge. I've got a thin tube about 1" diameter & cut four slots in it with a grinder, it works ok but is not posh. You might be able to crack the bolt out with a windy gun or impact driver. Once the cartridge is out you'll see how it locks in & be able to make a decent one.

I've heard of shaved broom handles being stuffed down the side of the cartridge to get the bolts loose too.

[Buddynq]

Good plan Hooli. They want a fortune for a genuine one.
In the parts manual http://gsx1400owners.org/forum/index.php?action=downloads;sa=downfile&id=1 (page 71)
There is a bush, Guide (Part 8) and a Bush, slide (Part 21)
Is that the bush you were talking about?

[Hooli]

Yup, 8 & 21 were both equally worn in mine. You can tell as the bearing material is a totally different colour to the backing. I think it was a black teflon coating & copper behind but not 100% on that. They just slide on & off so nothing more technical than a small screw driver to lift a corner out of their slot needed to swap them. I smeared fork oil behind them & over them to make sure they slide in nicely.

Those four parts cost me about £75 in this country, but well worth it for the difference they made.