FFP – Function Formed Primary


The primary drive housing is the most recognizable piece of architecture on American motorcycles. It is centrally located and transfers power from the engine to the transmission. We sculpted our forged 6061-T6 Function Formed Primary (FFP) to enhance the natural mechanical beauty of the elements inside. A SolidWorks 3D model of the clutch, chain, starter pinion, and motor sprocket was created and then we sparingly started adding material to wrap around those elements. No extra aluminum, just mechanical beauty. And there’s a glory hole in the middle for that open look, with the benefits of the chain intact. FFP fits all Softail models, Evo and Twin Cam without modification. Compatible with stock 66-tooth and 102-tooth clutches, compensating sprocket, chain, and starter motors. Each primary kit includes an inner primary housing, outer primary cover, 1-piece starter jackshaft, chain adjustment shoe and mechanism, gaskets, and fasteners.  For performance junkies with mountain motors, the FFP has an optional internal outside bearing support (FFPS). Applications above 150 ft-lbs require the outside clutch support to keep the transmission mainshaft from flexing. The outside bearing support version is the first enclosed, wet primary available to have this feature. Belt drives have been available for years with outside supports. Our King Kong Clutch is required with outside support spider.


-The FFP is the only complete aftermarket ‘wet’ primary set up in the industry

-6061-T6 forged Inner and Outer

-Externally adjustable primary chain

-1 Piece starter jackshaft for strength

-Fits stock and custom application

-Optional bearing support with King Kong Clutch offers an unmatched torque capacity of 250ft/lbs of continuous load

-Available in Black or Polished -Starter pinion compatible with 66 tooth  clutch ring gear

-Compatible with several different primary ratios, see technical

– 2 Year limited warranty


Included Parts


Primary Finish Options
The FFP comes in 2 different finishes

Show Polish Finish

Black Anodized Finish


High Torque Bearing

High Torque Bearing

The Function Form Primary comes standard with our High Torque Bearing kit, pn 189-56, installed.  This removes the stock (pn 34091-85) inner bearing race that has been used on Big Twins since 1985. This factory inner primary bearing rides on this race. By design, this race press-fits onto the transmission mainshaft. This system works fine for stock engines. 100 HP+ engines will make this race walk on the mainshaft. If it walks inboard, it will damage the maindrive gear seal and cause a transmission oil leak. If it walks outboard, it will cause a primary oil leak. Our high torque bearing kit eliminates this condition and that is why it is standard.


Bearing Support In FFP

Optional Bearing Support

Being the ultimate in high horse power clutches for Big Twins we had to design a bearing support to keep your mainshaft from bending under severe loads. The bearing support features a billet 6061-T6 design which is mounted to the King Kong Clutch using 3 alignment dowels and utilizes a heavy duty roller bearing. The Bearing Support version of the FFP is designed to work with the BAKER KKC ‘King Kong Clutch’ only. The derby cover of the primary has a bearing race pressed onto the snout of the cover which slides inside the bearing of the support when installed to keep the clutch assembly true to the world no matter how much horsepower you can throw at it. To learn more about the King Kong Clutch ‘KKC’ Click Here


External Primary Chain Adjuster

Chain Adjustment

The FFP is the only primary in the aftermarket that features an externally adjustment primary chain adjuster.  No removal of the outer primary is necessary and no gaskets are used.  Just remove the inspection cover and adjust the chain to specification with the adjuster screw on the bottom of the primary (as shown)



PN                                                                Description
4100-FFP-P                           Polished (66 tooth ring gear applications only)
4100-FFP-B                           Black Anodized (66 tooth ring gear applications only)
FFPP-KKC*-OBS                  Polished with KKC and Outboard bearing support
FFPBA-KKC*-OBS               Black Ano with KKC and Outboard bearing support

*Specify tooth count for sprocket, input 35, 36, 37 or 38 depending on your desired primary drive ratio.


Primary Configurations

Motor Sprocket Clutch Sprocket Chain Length
21 36 80
22 35 80
24 37 82
25 36 82
27 38 84
28 37 84

**Primary chain fitment was done with Diamond brand primary chains.  We have found that Regina chains will not work with all of these combinations.

Recommended upgrades

– King Kong Clutch

– 9 Plate Clutch

-Torque Box

Click on any of the images below to learn more

King Kong Clutch

SP9- Street Performance Clutch

Torque Box


Spectro Primary Oil, 85W

Recommended Fluid / Level Picking the right primary fluid ensures the life and durability of your primary, that’s why BAKER recommends a 85W primary oil. If using our King Kong Clutch ATF (Dexron/Mercon) fluid is required. BAKER does not recommend the use of Syn3 (20W-50). For Bert’s  article on ‘Oil & Spiders’  Click Here


BAKER Function Form Primary Fluid Capacity Dry: 10-14fl-oz


Instructions   BAKER FFP install instructions with exploded views Click Here







Polished FFP, pn 4100-FFP-P

Skeeter Todd’s XWR-T with FFP, pn 4100FFP-P, custom mid controls, black inner and polished outer

Jerry Covington’s Psycho, FFP custom engraved, full

Jerry Covington’s Psycho, FFP, custom engraved



BAKER DRIVETRAIN| 9804 E. SAGINAW, HASLETT, MI, 48840 |1-877-640-2004| 517-339-3835 | FAX: 517-339-4590 @2012 BAKER INC