The 4CS is well known for having a harsh mid-stroke while blowing through on larger bumps and bottoming out.
To do the conversion, I removed the big blue O-ring from the outside of the damper rod seal head and removed the seal from the seal head that seals the damper rod. Doing this allows the oil to flow between the chambers just like an open-cartridge fork.
Since the conversion I have been able to run an air gap of 65mm, which holds the fork much higher in the stroke without becoming harsh. It also means the fork stiffens up much faster and doesn’t blow through.
The conversion also means it is much easier to fill the fork with oil. You can now fill it from the top and bleed it through by pumping the damper rod up and down until all the air has been bled out. This conversion, combined with the correct spring rate and the right valving, has given me much more confidence in the fork.
I will continue to test this suspension and keep everyone informed on how it is performing. Keep an eye out for a “How To Pro” on converting your 4CS fork to open-cartridge in a forthcoming issue.
I am still running the Bridgestone Battlecross tyres with the X20 on the front and the X30 on the rear and they are holding up very well. I believe in running the same compound on the front and the rear but this time I decided to give the X20 a go on the front and have been very impressed.
The softer rubber is holding up well and I can’t fault the X20’s performance. The X30 is still a great tyre as it is wearing very well and can handle hard-pack, rocky tracks better.
Overall the 350 is running well. There have been no engine mods this month but I still feel some extra torque would not go astray.
TOTAL HOURS 25
MODS THIS MONTH Convert fork to open cartridge
MODS NEXT MONTH PowerParts
Technical Editor Mat Boyd
This long-term update was published in ADB issue #441 – June 2016.
