2.9 Marzocchi 40mm - 41.7mm

    KTM 125MX 1983, Early to Mid 1980s Marzocchi, KTM, Can Am, ATK

This is the stock damping rod head.

The spring seat on top of damping rod must be removed and replaced with an Emulator Adapter.

The stock spring seat is a snug fit. You may need to tap it off.


FPEV AD3811 P Emulator Adapters are a tight fit on the head of the damping rod. When they are installed correctly they cover the cross-drilled holes. This blocks them off redirecting the flow through the Emulator.

Sometimes the top of the damping rod has dings on it. You may need to dress it up with a file so the adapter can go on.

NOTE: 41.7mm (42C) Single Damping Rod Forks same procdure. FEGV 3812 Kit is 1 FEGV 3801 Emulator wtih FPEV AD3811 Emulator Adapter for the single Damper Fork Style used on some models, others are Dual Damper 41.7mm Forks. 

Remove the Check Barrel

There is a plastic check barrel near the bottom of the damping rod that must be removed. Tap out the brass roll pin and remove the barrel out the top.

Damping Rod Compression Feed Holes Modification

Drill out the 5 and 6mm holes at the bottom to 8mm (5/16") and add another set 10mm above the top set at 90 degrees to the originals. This will give you a total of six enlarged holes. Chamfer and deburr inside and out. 

Do not drill out any other hole further up the damping rod or you will lose rebound damping.

Rebound Check Valve and Bottoming Assembly

If you remove the Rebound Check Valve mechanism from the bottom of the fork tube for any reason (rechroming or cleaning) this is the order it goes back together.

This assembly goes in from the bottom of the fork tube.

The Check Valve recess in the sleeve faces up.

Bottoming Cone

Refer to Standard Emulator Instructions to complete the installation.