Ihave a 1980 fxsb that has a 103" shovel and rotary top trans. i had the trans repaired last summer and when i put it back in the bike,I found that shifting from first to second it did not hit any detent or stop and the shifter went way to far, the linkage got jammed against the trans case.
Is this problem linkage inside the rotary top, or is the linkage on the side worn or misaligned ? any one know?

 

Twin Cam engine transmissions have a shift drum that moves the shift forks that select the respective gear. When the shift drum is turned by depressing the shift lever, a detent holds the shift drum in position. If the transmissions are similar I'd say the detent isn't working. The key is that you CAN select gears so the selector is working, as is the shift drum and forks.

 

Are you sure the shift forks are installed correctly??
Also, the shift clutches(shift dogs as some call them) could also be installed incorrectly.
Those gearboxes are very easy to address.
We used a highly modified version of one to help our 108" AHDRA Modified Class bike, run a ton of 8.90's.

 

The op is asking about a 4 speed transmission...

The transmissions are completely different.

Off Topic Note: not all twin cam transmissions are the same, there are 5 speed and two versions of the 6 speed. Some 5 speeds have the shift detent on the drum, but some do not.

 

4 speed shifting has a lot more (about triple) the throw (amount your foot has to travel to shift gears) of a 5 speed or later transmission.

 

On the late 4 speeds the paw carrier wears quick. All I have built in the last 10 years had to have this part replaced. Another of HDs not so bright ideas.