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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
  • 1990-2006 Softail

Primary Chain: The pitch count of your chain depends on the tooth count on your clutch sprocket and motor sprocket. For further information, please contact us through the website chat, email us at, or call us Monday-Friday 8AM-7PM EST/EDT at 517-339-3835.

Outboard Bearing Support: If you have a King Kong Clutch, you will need the outboard bearing support.

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
FFP-410002                          Polished (66 tooth ring gear applications only)
FFP-4100011                        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 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

Standard Gear Case Finish Examples (Not applicable to all products)




Wrinkle Black

These example finishes are intended to show the exterior treatments of cases, top covers and doors.

TERM AND CONDITIONS                                                                                         

  • BAKER Drivetrain reserves the right to change prices, terms or policies at any time without notice.
  • Orders can be pre-paid using Visa, MasterCard, American Express, Discover or PayPal.
  • All orders not pre-paid will be sent C.O.D. certified check or money order only unless pre-approved for company check acceptance.
  • Any orders from outside the USA must be pre-paid in US funds via wire transfer; a $30 transfer fee will apply.
  • Prices shown are F.O.B. Haslett, MI.


BAKER™ transmission assemblies, transmission kits, primaries, and oil pans are guaranteed to the original purchaser to be free of manufacturing defects in materials and workmanship for a period of 5 years from the date of purchase or up to 50,000 miles. BAKER™ clutches, kicker cover kits, belt drives, F6F kit, reverse systems, covers and accessories are guaranteed to the original purchaser to be free of manufacturing defects in materials and workmanship for a period of 2 years from the date of purchase or up to 24,000 miles - whichever occurs first. If the product is found by BAKER™ to be defective, such products will, at the option of BAKER™, be replaced or repaired at cost to BAKER™. 

In the event warranty service is required, the original purchaser must call or write BAKER™ immediately with a description of the problem. If it is deemed necessary for BAKER™ to make an evaluation to determine whether the transmission assembly or transmission kit or accessory is defective, the entire transmission assembly, whether originally purchased as an assembly or kit, must be properly packaged and returned prepaid to BAKER™ with a copy of the original invoice of purchase. If after an evaluation has been made by BAKER™ and a defect in materials and/or workmanship is found, BAKER™  will, at BAKER™  option, repair or replace the defective part of the assembly. 


Due to the uniqueness, low price and assembly outside of typical production process of products indicated as Insider Special products, purchasing these Insider Special products include a warranty so to guarantee the original purchaser to be free of manufacturing defects in materials and workmanship for a period of 1 year from the date of purchase or up to 12,000 miles. We have provided extended options for you to purchase below. 


Any merchandise returned for any reason (exchange, credit or modification) must be accompanied by a Return Goods Authorization (RGA) number or it will be refused. Call BAKER™ to obtain this number prior to returning goods for any reason. There is a 15% re-stocking fee for all returned items. BAKER™ is not liable for any shipping charges. 


NOTE: Limited warranty does not cover labor or other costs or expenses incidental to the repair and or replacement of BAKER™ products.

This warranty does not apply if one or more of the following situations is judged by BAKER™ to be relevant: BAKER™ OEM transmissions; (these are subject to the OEM manufactures warranty only), Improper installation, accident, modification (including but not limited to use of unauthorized parts, transmission oils or lubricants), racing, high performance application, mishandling, misapplication, neglect (including but not limited to improper maintenance), or improper repair. 

BAKER™ shall not be liable for any consequential or incidental damages arising out of or in connection with a BAKER™ transmission assembly, transmission kit, component or part. Consequential damages shall include without limitation, loss of use, income or profit, or losses sustained as the result of injury (including death) to any person or loss of or damage to property.

BAKER™ transmissions, transmission kits and accessories are designed exclusively for use in American V-Twin motorcycles. BAKER™ shall have no warranty or liability obligation if BAKER™ parts are used in any other application.

If it is determined that a BAKER™ product has been disassembled during the warranty period for any reason, this limited warranty will no longer apply unless you were instructed to do so by a BAKER Drivetrain technician for diagnostic purposes.

The words H-D®, Softail®, FXR®, Dyna®, FLT®, FLH®, Sportster®, and Buell® are registered trademarks and are for reference only.

FFP: Function-Formed Primary for Harley-Davidson 1990-2006 Softail motorcycles
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FFP: Function-Formed Primary for Harley-Davidson 1990-2006 Softail motorcycles FFP: Function-Formed Primary for Harley-Davidson 1990-2006 Softail motorcycles
Web Product ID: 5211731267
Baker Drivetrain Team Illustration