softail conversions

DYNA Softail frame 

It took 2 years of designing and testing, here it is, ready to take either evo or twin cam dyna engine / trans units.


Why build a dyna softail frame? Well we do one for all the other Harley models and we wanted to complete the range, plus, there are a lot of dynas out there, which as they age, will become good project material. Even a new one is good value as a starting point. It was also a challenge; we haven’t seen any others out there which, in our opinion, will work properly. There are a lot of pitfalls in designing a rubber mount softail frame that are not obvious to the casual observer. We are well aware of these through our experience in developing our FXR softail.


Designing a softail frame for a dyna posed a number of difficulties; the oil sump prevents the use of conventional softail type shocks, which in any case cant be successfully used on a rubber mount frame without overloading the rubber mounts.

We couldn’t adapt the dual linkage monoshock set-up successfully used on our FXR softail, as the long primary masks the end of the swingarm pivot, preventing the use of FXR type rubber mounts. We didn’t want to add a mickey mouse bracket to the back of the trans to relocate the swingarm pivot rearward, because- quite apart from being tacky engineering- it would have meant making the frame 2” longer, compromising drive belt usage.

We wanted to keep the swingarm pivot where it is, we wanted a rising rate monoshock suspension set-up and we wanted an effective rubber vibration isolation system (Theres one rival out there who thinks blocks of polyurethane plastic will absorb the vibes- we think his customers will loose their fillings!)

The solution we came up with was to rubber isolate not only the engine, trans and swingarm, but also the whole monoshock/ linkage assembly in a special suspension support cradle which is mounted in bearings around the swingarm pivot and on rubber mounts top and bottom. This allows the engine unit to articulate without transferring vertical plane vibrations to the suspension cradle. It also protects the front rubber mount from suspension forces.

With a set-up like this, the rear rubber mounts must bear suspension forces, so stock type mounts would not be suitable. Many months of trial and error testing finally resulted in an effective and durable combination of rubber mountings.

Since the swingarm does not pivot on the frame directly, there was no need for the frame to have heavy steel sideplates. Instead, a more aesthetically pleasing tube runs where the ugly factory forgings would otherwise be. The sideplates of the swingarm (no losing them here) go pretty well unnoticed on the assembled bike.

By keeping things close coupled, the swingarm only had to be 15mm longer than stock-easily allowing belt rear drive with several different belt/pulley combinations.

Lots of folks rode the (in primer) test mule, some made helpful suggestions and all complimented its handling qualities

Engine offsets for the enormous tyre brigade can be easily accommodated, although this must be stipulated upon ordering. We recommend a year 2000 dyna belt (133t x 28mm) on a 65t rear pulley with ” offset to run a 200 tyre or ” offset to run a 180 tyre. We don’t recommend more than ” offset for street use. Bigger tyres can be had via offset kits or RSD gearboxes

Zodiac and others sell offsetting kits. These re available with 12mm, 25mm & 45mm longer gearbox mainshaft and 5th gear / pulley shaft. The 12mm kit will get you a 180 tyre, the 25 mm kit will allow you a theoretical 220, (or a 200 with the older 37mm belt) and the 45mm kit should be used for 230, 240, and 250 tyres You'll need a year 2000 up 28mm belt to go with these. 

RSD gearboxes should be used for 280 and up tyre widths.

Because of the extra 15mm frame length, you need to use a 65T rear pulley and a 133T belt.

Theres lots of room for the battery and electrics under the seat, and a battery carrier is included in the basic frame package. 

Steel side panels are 90 extra, Stainless side panels are 140 extra..

Brackets for seat, fender struts and footrests are the same as on standard softails, ensuring a broad range of accessory choices.

As with all our frames, the dynasoft is made from quality seamless tube and TIG welded in accurate jigs. Any rake and/or stretch specs can be ordered at no extra cost.

Price for this frame assembly complete: 1700. 00


A right-side-drive version for a 280 rear tyre.