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Amazing Rivera/Primo 4-speed Conversion Install

This Turns a 4-speed Shovel into a late-model 6-speed, with a modern starter to Boot

By Bandit, with Photos by Sin Wu

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There's a rumor that over one million Swingarm Shovelheads still roam the highways. I say, "Bullshit." Let's count 'em. That's beside the point here. Ben Kudon, the marketing directors of Rivera/Primo came up with this hair- brained scheme. "Let's fix all Shovelheads," Ben said. "We can do it for a decent price and give Shovelhead riders late model starters, a 6-speed tranny with a spline shaft and a state of the art Rivera primary and clutch system." He was right. River/Primo could offer all these upgrades to Shovelhead owners for the price of some primary drives alone, less than three grand. Ben began to look like the Shovelhead Moses.

Here's shots of the clean 1975 FLH with stock 4- speed tranny and a belt stuffed in the stock primary.

So we went to work finding a local suspect, Roger Brown, who was tired of his old 4-speed tranny and the starter that only worked occasionally. With this system he lost his kicker, but Primo has kicker systems designed for their 6-speed transmissions. We jammed to Larry Settle's shop in Harbor City, California, near the center of Los Angeles and not far from the gruesome Bikenet.com Headquarters. Larry's shop has been around longer than... He wouldn't tell us. It's in the back of an industrial block structure as far off the road as possible. It's sorta an industrial strip mall. On the positive side, painters and pinstripers, surround him, and Yvonne Mecailis performs artistic magic on bike parts just up the lane.

Shot of the new trans ready for action.

Larry has been working on bikes since, well, you know. He'd rather not say. He was a good man to perform this daunting task, and immediately started asking Ben questions. "So, what do you want me to do with the speedo cable?" Larry inquired.

The master, Mr. Settle, checking the documents.

Here are a couple of other curious items needing attention: The old stock clutch cable wouldn't work and a new one wouldn't readily fit in the stock lever. Shift linkage needed to be reworked. Some starter relays might get in the way, but after you consider the hiccups, the benefits of this mod were substantial. We'll go through each and every alteration and explain Larry's solution. This bike also sported floorboards and Larry machined a bracket so the rider could continue to run them.

First thing, remove the battery cable.

Let's get started. Larry wouldn't let me touch a tool, so I took notes like a mad dog and listened to the Rivera/Primo team bicker. "Don't touch a tool, Bandit," Larry barked. "You ain't a mechanic here."

Larry ended up removing both pipes.

He lifted the seat and removed the battery cables first, then started removing the massive battery box. "I have to cut on it," Larry explained as he pointed at the supplied directions and template for cutting the back battery bracket that bolts to the oil bag. It needed cutting also.

Removing the massive FLH battery.

Then he removed the Ford style starter relay and the battery box.

This bracket was shit-canned for something completely new.

Here's what Larry came up with later.

Larry left the oil bag in place. "I don't think I need to remove it for cutting," Larry said then discovered a broken stock bracket ear on the rear left corner. The oil bag needed to be removed. Also the battery box mount extending to the tranny needed to be adjusted.

You wouldn't want to handle this task of removing the solenoid with the battery still connected…

The old troublesome style starter.

Next Larry removed the old starter in one piece to retain it. "It's a Shovelhead," Larry said. "I don't have to loosen the tranny bolts, they're already loose."

Ah, the famous cardboard oil drain tool.

Then he drained the oil, discovered the broken oil bag tab and disconnected the solenoid. Next the primary was removed which contained a broken belt, because oil had leaked into the primary and weakened the belt structure. He then removed the clutch basket, which had left handed threads and the engine pulley with right-handed threads.

There's the oil damaged belt.

The nut holding the clutch basket in place is left- handed and so is the massive nut holding the pulley in place.

On the other hand the engine pulley nut has right-handed threads.

Larry started working on bikes at 19 and went to work for Lomita Harley in 1971. He began to loosen up. He bit off the safety wires holding the inner primary fasteners in place and removed the inner primary. "Rivera has universal electronic speedos that will work on 1975 FLHs as well as many other years," Ben commented, while Larry removed the rear drive chain.

"It's all up to the customer," Larry said. "We may end up running a speedo drive off the front wheel and maintain the stock speedometer."

Here's a shot of the front wheel speedo drive he went with later.

He's unbolting a chunk of the inner primary (motorplate) that won't be used in this application.

As it turned out the new 6-speed transmission base plate is a different configuration from the stock 4-speed unit. So Larry grabbed the supplied Rivera/Primo job. I asked Ben how Rivera/ Primo was able to offer such a deal on all these elements.

The old 4-speed, without the kicker arm slipped out the left side.

"We worked really hard to keep the prices low on this 4- to-6-speed conversion kit," Ben said. "The benefit of getting rid of the tapered shaft tranny is substantial and this 6-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."

Larry removed the massive starter Relay under the battery box, left it wired into the system and set it aside.

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.

"We worked all the elements to fit with all the stock components," Giggie said. "There's over a million Shovels available from 1970 to 1984, and every one needs one of these systems." A major mod was a massive notch behind the transmission to allow the new tranny to work with the stock swingarm configuration.

"The rotary top transmissions from late '79 to '84 can't run electric-start, 3-inch belt drives," Ben added. "They won't fit and allow a brother to update his system."

Here's the Giggie Shovelhead notch in a Softail Trans case.

Here's the news Softail style tranny plate from Rivera/Primo.

Larry unbolted the stock black tranny plate and removed the old H-D 4-speed transmission out the left side of Brown's bike. 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 could be bolted in with out the transmission and the tranny fit up and over the plate.

The new 6-speed heading home.

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 1/4-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 Giggie and I jammed back to the Bikernet Interplanetary Headquarters to steal a sprocket.

Larry installed all the tranny fasteners loose for alignment checking purposes and to prevent binding.

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.

Checking linkage dimensions.

After terrific Mexican food at Bandit's Cantina, Larry replaced the sprocket and used Loctite on the massive shaft nut and the Allen keeper fasteners. As it turned-out a simple solution fixed the shift linkage formula. Larry made sure nothing would bind as he installed a 12-inch Evo linkage arm to the stock Shovel foot shift control arm and the Rivera/Primo arm on the trans.

Installing the lock plate around the new chain sprocket nut.

"This primary motor plate will take a spin-on oil filter," Ben pointed out. "It comes with the nipple, and Rivera/Primo makes an optional set of mid-controls that bolt up with some minor modifications."

The special Giggie bracket for the lower rear corner of the inner primary. It works with the transmission case notch.

The transmission was in place at this point. The complete Rivera/Primo instructions called for removing one of the brackets off the inner primary and replace it with a special Giggie designed boss that aligned the inner primary with the trans and dodged the swingarm portion of the frame. Larry torqued the ¼-20 Allens to 12 pounds.

This is the time to replace the chain, before the inner primary was installed. Sometimes feeding a chain over the sprocket can be a pain in the ass.

Then he installed the ½-inch engine to inner primary plate adapter, then the inner primary. At this point the transmission was left loose to allow it to align with the engine using the Rivera/Primo massive billet inner primary to pull the engine and trans into perfect alignment.

This is the new inner primary showing the mid controls plug on the bottom and the oil filter fitting on the top. We didn't use either one at this point.

This is where we noted one of those little annoying tech install secrets to making the install a smooth operation. The top front Allen must be in place in the inner primary as it's slipped into place, or we couldn't get it in without removing the shifter control plate. Larry used a pinch of Red Loctite on all of the Allen fasteners and tightened them to 24 pounds of torque.

The Torque Wrench master.

These outer primary stands are massive and set into the inner primary.

Next we attempted to install the new Rivera/Primo starter and ran into the rear fender. Giggie modified the standard starter to allow the solenoid lead to clear the oil bag and battery box. Unfortunately the bike owner, at some time in its long history, replaced the rear fender with a stock replacement aftermarket job. It fit slightly different than a H-D factory fender and we had to relieve the lower area behind the starter.

This shows where the starter would smack the fender.

Larry's attending college at Long Beach State at 59 years of age, but he ain't taking art.

Note: For this tech Larry used a die-grinder to remove fender material and we continued. Later the fender was refinished and touched up.

The Rivera/Primo Elements:
Price $2935
6-speed PowerDrive transmission
Brute 4 Extreme Open Belt
MonsterTorque starter
Tranny Plate
Hardware (less the bottom tranny nuts)
Rivera Pro Clutch

The Rivera/Primo starter is made in the U.S. and Canada with no rebuilt parts—all new. It contains permanent magnets and parallel gearing for more powerful and reliable starting.

Larry installed the starter jackshaft and began to install the pulleys. The engine drive shaft nut from Rivera/Primo was chromed so Larry wrapped it with Duct-tape to protect the finish. Larry used a straight edge to check pulley alignment. "The front pulley should run 1/8 inch off the inner primary," Ben commented. We weren't in alignment.

Bad alignment can be caused by several factors, including the alternator rotor. Larry made some precise measurements and determined that the back of the engine pulley needed to be machined .064 for proper alignment. He has machine shop capabilities and did the number to the pulley in 5 minutes.

Double checking alignment.

With the pulley machined the belt could slip into place.

Generally alignment falls in the other direction and Rivera/ Primo has a PX-1 shim kit to modify the engine pulley spacing. Rivera/Primo also has a clutch-locking tool to hold the clutch during torquing. Larry used an air wrench to pull the pulleys in place and tighten them.

Here's those bolts that were installed with anti- seize. They have locking tabs to keep 'em in place.

The clutch and primary drive was flying together. Ben pointed out that it's important to use Anti-Seize on the clutch studs. "The bolts extend through the clutch basket," Ben pointed out. "If they jam or are damaged and can't be removed, the clutch can't be removed without damaging components severely."

Here's the notorious jackshaft support.

Larry installed the jackshaft support with grease or Anti- Seize although River/Primo builds the support with a brass oil- lite bushing inside. Then he installed the massive outer primary stands. Larry installed the Gates belt that has a fiberglass core and rubber casing. "Belts are now extremely strong," Ben pointed out. "Wider belts are expediently stronger." Rear bearing supports are also available from River/Primo.

Larry removed the tranny side cover to install the late model style clutch cable and noted that we might need to modify the pipes. Also the stock front, tranny to battery box bracket wouldn't work and he had to make a custom job.

Larry spinning the cover onto the clutch cable.

Replacing the massive clip ring once the cable end was installed in the clutch actuating arm.

"We have kicker systems available for our transmissions," Ben pointed out. "We also build hydraulic actuated clutch covers for these units."

Larry pointed out that all the tranny cover Allen fasteners were not the same length and it's important to note which fastener goes where as they're removed.

Larry used this system to install the clutch end, then later machined the lever so the clip ring could be installed.

Larry removed the clip ring inside the tranny cover and carefully attached the new clutch cable end without loosing the ball bearings. "We need a '72-'81 cable pivot pin system to secure the cable to the handlebar lever," Larry pointed out.

Ben had a mistake free formula for adjusting the clutch action. It was included in the River/Primo directions. "Loosen the clutch cable adjustment, until the lever hits the handlebar grip," he said. "Turn the center clutch adjusting screw in until the handle just begins to move. Lock the clutch adjuster down hard. Now adjust the cable until there's 1/8 of play in the lever and you're good to go."

Tightening up the new River/Primo 6-speed.

Larry followed the formula and it worked like a charm. Larry tightened the tranny down against the plate first then the tranny plate after inspecting it for gaps. If there were any gaps, he needed to pull the trans and level the tranny with shims. He installed the laser-engraved derby cover.

Next Larry started marking and die-cutting the battery mount for clearance. He then moved onto the oil bag. He discovered if he removed the feed line fitting off the bottom of the oil bag it would slip in over the top of the trans from the left side toward the read of the bike. It was sort like tight a puzzle, but it worked.

Larry fit the battery box and oil tank a couple of times while modifying the tabs for the perfect fit and good clearance over the top of the tranny. At this point it was obvious why Giggie removed the starter solenoid bung. It would have smacked the battery and oil bag mount.

Rivera/Primo includes a rubber starter cable boot to protect the starter positive lead. Larry added the connector for the starter solenoid lead and connected it to the Rivera/Primo lead off the Power starter. We were getting close. He replaced the feed fitting on the bottom of the oil bag and installed the battery box.

Larry pointed out that H-D made at least three different battery boxes during Shovelhead history. There were kickstart boxes, FX, FLH and Night Trains. Each one could require slightly different mods for this system to work. "Yeah," Larry said, "they also used three different starter relays over their 18 year history, including: Delco, Bosch and Ford relays."

He hooked up the Ford style cumbersome starter relay and it fit comfortably above the new 6-speed Rivera/Primo transmission. "Don't forget the tranny vent hose," Larry warned us. Rivera/Primo also has an optional kickstand stop system available for their primary. Larry Installed the battery and it was nearly Happy Hour. He installed the battery cover and nerves were on edge as he installed the pipes. They fit without mods! He hooked the battery up and the acid test was about to unfold. They hit the button and nothing but a clunk sounded.

Larry, with all those years of experience, knew what to check first. He removed the starter jackshaft support with the oil-lite bearing and grease, checked it for binding and replaced it. Bingo, it started like a dream. "Let's party," Giggie said and Ben scowled.

Here's Larry's footboard bracket.

After the River/Primo gang left, Larry touched-up and went over the complete install. He road tested the bike and readjusted the clutch. He made a footboard mount attach to the Rivera/ Primo outer primary and machined the handlebar lever to allow a keeper clip to hold all the components in place.

Here's the machined lever for extra clutch pin space.

The bike was good to go with more gears, later-model transmission technology, stronger, longer-lasting starter and a proven primary drive and clutch.

Not bad for less than three grand. It was margarita time.


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Reader Comments

Informative and entertaining good job

Bill Moore
Greensboro, NC
Thursday, December 1, 2011
Editor Response Thanks, mean a lot to our staff.
Nice! How about if you still want to run a closed primary and chain though?

Dago, CA
Wednesday, November 30, 2011
Editor Response Since this is a Rivera tech, I'm sure they want you to use their belt drive. I sent your e-mail to Ben Kudon. I'll tell you how it can be accomplished, or not...
Good article, always liked Primo stuff. Now, what are you doing with the old setup do you want to sell it?



wellington, New Zealand
Friday, November 25, 2011
Editor Response You'll need to contact Larry Settle in Harbor City. It was a customer's bike.

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