Mr. Potato Head® transmission was conceived in R&D a few years back to study the configurational possibilities of putting universal bosses on a featureless tranny case. Just like the Mr. Potato Head® toy, you can end up with a genetic hermaphrodite with a little off-the-menu creativity. The universal tranny case accepts an A-flange, B-flange or Evo flange. It also accepts all kinds of tail stocks. This exercise yielded the easiest solution to offsetting a tranny case side-to-side or up-and-down in short production runs. The RT250 vision began at Rolling Thunder when they divulged plans to develop a FL-type Bagger frame that was setup for a 250 tire and Softail length primary in a balanced right side drive chassis. They approached us about doing a special tranny that was specific to this frame.  Mr. Potato Head® technology finally found its first home and we named it the RT250 project.


– Utilizes stock Softail primaries or BAKER FFP

– 6061-T6 billet case construction

– Tranny is offset ½” to the left to tuck the drive belt/chain inside the frame rail

– No ½” motor sprocket extension required; tranny is slammed against the inner primary

– Tranny mainshaft is ½” shorter than stock

– Oil bag is separate and below the tranny case for superior cooling

– Frame has +2” in backbone for additional primary length

– Stock Harley® FL frames converted by Rolling Thunder and original VIN retained for no registration hassle

– Frames accept stock seat, bags, tank and front end

– Backed by a 5-year limited warranty


Case Finish Options

You have 2 different options for case finish on the RT250 RSD.

Show Polished Finish

Wrinkle Black Finish


Engine Fitment

The Mr. Potato Head transmission is the only transmission on the market that can bolt to Evolution, TwinCam A or TwinCam B engines.  This makes the transmission versatile for whatever your powerplant may be.  All variations are specifically designed to use a Softail length primary giving you the most options for your primary.


Linear Detent Plunger

Shift System

Our 6 Speed shift system with linear detent guarantees smooth shifts every time and  ensures that finding neutral is a easy chore. We mount our shift drum on a fixed spindle with roller ball bearings. The smoothest manner possible. The plunger rides over the ‘clover leaf’ peaks during operation (shifting) and when shifting into neutral pops into a pocket. This system lets you feel that you’re shifting into neutral. No more guessing. Shift drum features more aggressive timing on the fork groove profiles and is case hardened to 58 Rockwell for wear resistance and crisp shifts. We built our reputation on smooth shifting 6-speed transmissions; our drum designs benefit from the engineering lessons learned.



All DD6R gearsets are made out of 8620 steel, gears are shaper cut before heat treat then precision ground with diamond coated tooling after heat treat (58-62 Rockwell ‘C’). This extra steps ensures not only a quieter gear pair, but enables much tighter backlash control. The gearset is a combination of helical and spur gears to yield silent gear operation. The dog teeth are backcut at a 1° angle to optimize the smooth shift possible, while standard gearsets are cut to a 4° angle. The mainshaft is unique with 1st main gear being incorporated as part of the shaft, the countershaft also features a unique 1-piece design with 6th gear.

RT250 RSD Gearset


DD6R Shift Forks

Shift Forks

Our investment cast shift forks are made out of 4140 then dipped in a hard chrome plate bath for wear resistance, also designed with oil reliefs to ensure proper lubrication and wear resistance on fork blades and shift dogs.






Low Profile Pulley Cover

No Offsets

With the RT250 being developed around the stout 250mm rear tire, we wanted to do everything we could to keep a Zero offset driveline.  With using design data from our DSSC project and our common RSD’s we did just that.  Starting with the primary side.  We took a full 1/2″ width out of the case so that the primary does not have to be offset out.  We also shortened the mainshaft 1/2″ to tuck the clutch and primary close to the bikes C/G.  On the right side, to keep the belt inside the frame rails we developed a new low profile pulley cover and pulley.  This design utilizes a 20mm belt width and keeps the belt tucked in between the frame rails for a tight Factory look.





Gear Ratios


Standard Ratios
1st Gear 3.45
2nd Gear 2.56
3rd Gear 1.87
4th Gear 1.44
5th Gear 1.15
6th Gear 1.00
Effective Ratios
1st Gear 2.94
2nd Gear 2.20
3rd Gear 1.61
4th Gear 1.24
5th Gear .99
6th Gear .86


PN Description
RT250*-P  RT250 Transmission assembly, Polished
RT250*-B  RT250 Transmission assembly, Wrinkle Black

*Specify “A” for A-flange, “B” for B-flange, and “E” for Evo Flange; dependent on your engine setup


Recommended upgrades

– King Kong Clutch

– SP9 Street Performance Clutch

– Function Formed Primary


Click on any of the images below to learn more

King Kong Clutch

SP9- Street Performance Clutch

Polished FFP



Spectro Oil BD-75140

Recommended Fluid / Level

Picking the right transmission fluid ensures the life and durability of your transmission, that’s why BAKER recommends a fully synthetic GL-5 rated gear weight oil of 75W-140. If a GL-5 rated gear lube is not available, these commonly carried viscosities (weights) will work 75W-90, 75W-140 and 85W-140. BAKER does not recommend the use of Syn3 (20W-50). For Bert’s article on ‘Oil & Spiders’ Click Here




BAKER RT250 RSD Fluid Capacity Dry: 22-24fl-oz

BAKER RT250 RSD Fluid Capacity Wet: 18-22fl-oz




Frame Lock’s Turbo Charged RT250










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