WP 4860 MXMA CC Fork
These forks are used in many SX and SX-F Models post 2007.
Some later model Husabergs will also used these fork – example pictured are from 2013 KTM 350 SX-F (EU).
Check your owner manual for the model of the fork
that is on your motorbike
CC stands for closed chamber, sometimes refered to
as twin chamber or bladder fork
Helpful YouTube clips
- Take apart fork [Jeff Slaven]
http://www.youtube.com/watch?v=we1T0J1Z-hk - Bleed Closed Cartridge [Jeff Slaven]
http://www.youtube.com/watch?v=RlgjFNMlxyw - Another handy clip (not a WP fork though)
http://www.youtube.com/watch?v=eru0iV8sU8Y
Special Tools Used
- Compression Bolt Removal Tool – WP 4860 MXMA CC
- Fork Seal Driver [48mm]
Although the needle mentioned above is one designed for this purpose, one
can be made with some imaginationand a grease nipple. Try get a small hand
pump with a low pressure guage. We didnt have success with a foot pump used
for bicycle tyres. Something to do with the long hose makes getting low
pressure readings difficult (7-30 psi / 0.5 – 2 bar), watch the first
clip for demonstration
Also, just by chance, you can use the packaging from the motion pro
compression bolt tool as a seal saver with a bit of grease or oil.
This page combines a few sources to aid in the rebuild of a KTM WP4860 MXMA CC fork. If you are mechanically minded and can source your own motorbike parts tools and accessories and are prepared to take a chance at possibly being up for big dollars if it goes wrong, then do so at your own risk. Fortuneatly, I let my mate do the work, everyone needs one such MacGyver bush mechanic mate if you spend lots of time on the dirt tracks 🙂 There are two sets of fork and dust seals that I know of, possibly more that fit this. The latest is a DARK BLUE SKF seal, which is apparently better. I was sold the old set and was told they were fine. So far so good, but I am no pro.
The above picture shows an aftermarket spring seat that came out of my mates 2013 450 SX-f. He had his suspension modified and this was claimed to take the edge of when bottom out or hitting the bump stops if you would like to thing of it as a car. The main difference? The material is a hard rubber of sorts which must have a bit of play. He says he can feel the difference and I guess that makes sense.
As far as oil weights / viscosity, it is a dark art. I went with a 5w but to sum up a long thread , the weight of FORK oil really isnt suited to the common 5w/10w SAE system used to classify them. That is better suited to engine oil. Considering how fine the tolernaces and spaces are used for fork suspension (and shocks), a more detailed rating should be provided by the oil manufacturer. These ratings do exists and there are some good articles available if you want to lose a week of your life researching.
You will also find that different motorcycle manufactures have deals with different oil companies which makes it difficult to know what you should really be doing as they have magic blends which you must use. Make up your own mind. It is advertising, but it works. I have never been a KX fan, but seeing RV winning races makes me think that is the best bike, not the natural talent and hard work put in by such champs.
I know with me, a lot of it is in my head. My mate keeps trash talking me every time my front end is not responding on the track…I think your oil is two thin in your forks…. Other days it feels great.
And yes maybe it is, but nothing that can not be adjusted with some clicks. Weekend warriors dont have the luxury of a mechanic to change springs (although with air-forks now, this is now possible) oil and assist with making changes. Then again, most of us also think there is a a setting or modification that can be made to make us ride like a pro… BARRRRMM!!! Tell them theyre dreaming…
My mates front end on his 2014 450 sx-f never had any feel, even after having them professionally modified. After jumping on my bike and a 2009 530 exc-r , all on a MX track, he realised there was something wrong with his setup. He was quicker on the old thumper than his new you-beaut Mx-er. Although none of us could believe it, it made us feel better because my brother was on the pace after an absense of 14 months, and we thought that was very impressive since we thought he was on inferior machinery. Just goes to confirm in my mind that that suspension and handling is more important than outright power for the dirt. There are exceptions, sure. Go ride some sand dunes and you wont be wishing you had a small bore. Off the launches there isnt much between the three bikes we have (2013 350 sxf, 2013 450sxf, 2009 530 excr), and lets be honest, most of it comes down to the rider, the size of the kaahoonas, and risk vs reward.
