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Discussion Starter #1
The last couple of rides my bike has started to leave dribbles of oil on the lower right fork leg, and with the bike at 110 hours and having never had the forks serviced, I think it's about time I do them. The timing is go too. Up until now my bike has lived up my dads garage with no electric, no proper lights and crucially a 15 min drive away. While it doesn't sound far, but it means by the time you start any work you've already lost 30 mins or so, and another 30 mins to get home, so bike cleaning and maintenance has been really suffering. My new garage is awaiting the arrival of its roller door this week, so then my bike will be a 10 second walk thought the garden. It means I'm now going to be doing more work, and more work means excuses for more tools!

I've got all the basics, sockets, spanners, torque wrenchs etc, but what else do I need for fork service? I'll be doing a full OEM bush and seal kit, so they'l be coming properly apart. From watching videos, I think the 'special' tools I need are 1 17mm hex for the bottom, a seal bullet, a seal driver and a fluid level setting syringe thing. What do you guys use? Most of the bits are quite cheap, with only the seal driver being slightly costlier, but if a job is worth doing, its worth doing properly.

I'll get the KTM seal/bush kit, but any suggestions on oil and what levels? I'm only a lowly middle table sportsman, so working suspension is all I really need, but I have read that changing the air gap makes a difference. My bike is a '16 350 Sixdays and I'm about 75kg with kit. How do you check what springs are in it now, are they numbered?

Any tips will be appreciated,

Cheers
 

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It's very easy to service these forks as long as you have the tools. You need a pin spanner or similar to get the fork cap off.

Don't worry about the seal bullet. Use the corner of a freezer bag. You could easily make a fork height tool too.

If you had the bike from new and the springs are standard then I expect they are right for you. If not, the rate may be stamped on one end but maybe not on standard springs.

I think I run 100mm air gap. Just use decent putoline or similar 5w fork oil.

I don't know if they changed the forks after 2014 but on mine, the trickiest part is getting the base valve to seat against the cartridge to the right torque without it spinning. If you get that area completely clean of oil then it may go bit otherwise, I've found that I have to put the spring back in, compress the fork as far as I can using a strap, and the torque it.

Whereabouts are you? Someone nearby may have the tools.
 

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Discussion Starter #3
Ah, I'd forgotten about the pin tool thing, assuming it's the same as for a '10 ish OC fork then I've got one from when we changed the oil in my dad's bike a couple of years ago.

The rest of the tools should be less that 50 quid, and should pay for themselves over time.

I'll get stuff ordered over the next week or so and hopefully get the bike fighting fit ready for D2D!
 

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Having the tools yourself will save you money big time long term. I’ve never worked on a 4cs fork but they can’t be too different to anything else. Just make sure you lay things out in the order they come apart. This makes it super easy to remember the assembly order- especially if you get distracted and have to leave the job alone for a while. Cleanliness is everything. I lay clean paper down and place everything on that, preferably not on the floor. An air line is very helpful. Grab a 5litre can of brake cleaner to rinse everything off with.

My guess is with those hours you will notice a big difference in feel when they are all back together.

I don’t know when WP started using 4wt oil. It might have been forever but what I do know is different 5wts can feel very different, using 5wt stiffens a fork straight away even though commonly recommended. Silkolene 5wt feels stiff from day one compared to Rock Oil SVi which feels very slick in comparison. KYB 01m oil is amazing but expensive so only use that in the cartridge and cheaper oil in the outer chamber as that doesn’t go through shims. You’ll be surprised at the difference oil can make especially if you are a lighter rider on stock valving. Cheaper than a revalve too.
 

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I tried using Putolene 4 wt on my 2016 4CS, as it was the only aftermarket 4 wt I could find. I don't know if it was a dodgy batch, but it was utter shite. The stiction was horrendous, and when compressing the forks vertically off the bike, they made a horrible graunching sound and vibration. I then bit the bullet, and put genuine KTM/WP 4wt back in, and all was well ever since.
 

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I've used putoline HPX or some shit for the last 100 hours. The forks are pretty shit anyway but that oil seems to work as good as the original. Of course, now I'm wondering if I need to experiment...

On the 4CS, the cartridge oil mixes with the outer oil so no point using separate oils. Also, I guess you need an oil that fits the valving or else you'll change the function of the forks.
 

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Discussion Starter #8
Thanks for the replies guys. I'd like to say that my forks feel harsh or that they feel fine, but I honestly dont have any reference other than my old '10 excf and my brothers Husky. I set the clickers to a mid setting between from the book when I first had it and then just ridden it. The KYB stuff making things a bit slicker and plusher sounds good though. Having no reference on how much fork oil is, £24 a litre sounds OK for something important like suspension. How much do I need? Will 2 litres do it?

The only thing I can think of that I want more out of my suspension is I find the front bounces around a lot of rocky hills, but that could just be my (lack of) technique, lol.
 

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Just looked in the workshop, and I found the shit Putolene bottle, it was HPX R 4wt
Water and sand would have been better!
 

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2 litres'll do you. It's somewhere around 700ml per fork. There are plenty of good vids on YT showing the whole process. Mr Orange has covered pretty much everything in his post. Torquing the base valve is the biggest potential pain on the 4CS, but not that much of a pain once you have the technique (I was pogoing around my workshop before I cracked it) And you may be lucky and your guts won't spin.
 

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2 litres'll do you. It's somewhere around 700ml per fork. There are plenty of good vids on YT showing the whole process. Mr Orange has covered pretty much everything in his post. Torquing the base valve is the biggest potential pain on the 4CS, but not that much of a pain once you have the technique (I was pogoing around my workshop before I cracked it) And you may be lucky and your guts won't spin.
I use a ratchet strap round the top of the fork, and wheel axle to completely compress the fork, and the base valve comes out no problems. (and back in later!)
DO NOT point the fork towards yourself or anything important, as it the strap slips, it'll go off like a bomb!
 

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Don’t over tighten things either. All very soft and expensive. Use a torque wrench and it’ll come apart easy next time. Decent tools will also prevent damage....
 
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