Upgrading Shovelheads - Putting A Six In A Shovel -Tech

The old four-speed, without the kicker arm, slipped out the left side. "The prices have come down on our six-in-four-speed transmissions," Ben said. "The benefit of getting rid of the tapered shaft tranny is substantial and this six-speed shifts much smoother. It also allows riders to remove the old Shovelhead oil-through-the-primary system and replace the stock bullshit starter with a much stronger, more reliable auto-type starter."

We needed to salvage the nuts off the bottom of the trans for the new installation. An old friend of Bikernet's and a famous performance builder, Giggie, who worked for Departure Bike Works, then Compu-Fire, works for Rivera now. Giggie was also on hand to monitor our progress, since he was the designer/engineer who had to make everything fit. "Giggie designed the modifications to the tranny case," Ben said, "to allow the Softail case to fit in the early Shovelhead swingarm frames."

From the instructions, this shows how the battery box and oil tank brackets needed to be notched.

Here the oil tank is being removed so that the lower mount can be notched and the broken upper mount can be repaired.

Here's the new Softail-style tranny plate from Rivera/Primo. Rivera was kind enough to stamp an X into their Softail-style tranny plate to indicate to builders how the plate fit. The X was in the top left rear corner. The plate can be bolted in without the transmission, and the tranny will fit up and over the plate.

The new Primo six-speed heading home. A major mod to the transmission that made this all possible was a massive notch behind the transmission to allow the new tranny to work with the stock swingarm configuration.

Another item surfaced that any builder needs to consider. The tranny comes with a belt pulley, not a chain sprocket. "1981 Sturgis Shovels came with belts, then '82 and '84 and up were built with belts," Ben said. As it turned out we needed a 1/2-inch offset, 23 or 24-tooth chain sprocket. If the bike was bone stock, a non-offset sprocket might do the trick, depending on the rear wheel sprocket. We took a break for lunch and I jammed back to the Bikernet Interplanetary Headquarters to steal a sprocket.

The pulley had to go. Remember, left-handed threads. Rivera doesn't attempt to address the myriad of variables, since depending on rear wheel size they can be all over the place. The builder or owner needs to consider this aspect and plan for it.

Installing the lock ring around the new chain sprocket.