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Monday Edition

S&S Twin Cam Gear Drive Set Installed

Lifesaving Performance Upgrade

By Bandit with photos from Markus Cuff and Sin Wu
6/11/2010 4:11:41 AM



New Bikernet Security Beast, Cash, who works closely with his partner, Tank.

There's a code going around regarding Twin Cams. Lee Clemens pointed it out to me first, when he broke down on the way to Myrtle Beach on his FLH Twin Cam, with 25,000 miles on the clock. "The cam bearings disintegrated and took out the lower end," he said. The rumors are that the chain drive tension increases the load on the cam bearings and they begin to wear until they come apart between 10,000 miles, and as Lee Pointed out, 25,000 miles.


I discussed this with Gene Thomason of Gene's Speed Shop in Carson, California. We had an interesting chat about Evos and Twin Cams and which are the best. Gene and his dad, Gene Sr. worked for Bartels H-D in Marina Del Ray and for the Harley- Davidson fleet center for a decade. They know Twin Cams, every model and configuration. Gene Jr. is also an avid H-D top fuel drag racer, so he knows performance gremlins and how to deal with the stresses of performance enhancements.

Is he a surfer or drag racing maniac? That's Gene Thomason.

"The Twin Cam exceeds the Evo, especially when it comes to performance," Gene pointed out. "Since it's mated to the transmission, alignment is enhanced and the cases are heavier and stouter design to handle the rigors of big-inch engines. The Twin Cam configuration allows the pushrods to be shorter and run at less of an angle to the rockers. The hefty cams don't ride on the cam cover, but a separate plate specifically designed to hold the cams more securely and in alignment with the case more effectively."

I like the Evo for its pure tradition, historic refinement and minimal components, but everything he pointed out was correct and a consideration for performance-minded riders. I asked Gene if H-D would ever install gear- driven cams and he pointed out that noise is a factor. Factories are allowed a particular level of noise to comply with federal standards. That level applies to the entire driveline from the exhaust to the tappets.

"Harleys like their exhaust rumble, so they try to keep the driveline quiet," Gene said.

You'll notice that Victory runs a noisy gear-driven primary, but the exhaust is quieter to level the regulatory playing field. I also reached our to our resident Bikernet.com Tech Expert, Pablo. Here's what he said:

”I hope you replaced the inner case INA (H-D) cam bearings with Torrington roller Bearings. Get them from Drag or CCI. The new 96-inch H-D engines also use INA inner case cam bearings, just a larger size.

”The Twin Cam INA bearings have the same issues like the EVOs did. They don't hold up with any performance work added to the engine. Cams, heads, stroker kits, and high-compression pistons enhance pressure on internal components. The Torrington bearings have more rollers, more bearing contact surface, and better support.

“Good choice on the S&S gear drive setup for sure. You might consider one those billet cam plates also. Check your Flywheel run-out also.”



I rode the 2003 Road King, with a measly 12,800 miles on the clock, to Gene's Speed Shop on Normandie in the Torrance, California Gasoline Alley (310) 618-1908. We pulled the bags and immediately performed a dyno run for a reference, although I wasn't switching the cams for additional performance. I had mid-range SE-203 cams in the bike with Screaming Eagle Heads, two-into- one Screamin' Eagle Exhaust and Terry Components closed-loop enhancement to my H-D EFI system. The bike ran terrific. The Dyno noted 68 HP at 6000 rpms and 84 pounds of torque at 3000.

"A stock 96-incher puts out 52 horses and 65 pounds of Torque," Gene said while straddling the King in his dyno room.

We carefully removed the exhaust sensor before yanking the pipes off.

The 203 mid-range cam had .510 and .483 lift (intake and exhaust), and .234 and .239 duration. The S&S 570G cam set had .570 lift with .240/.255 duration. The S&S brochure point out the following benefits:

Reduced Maintenance: There are no chain guides or shoes to wear or replace and no debris from wearing guides or shoes to contaminate oil supply.

Consistent cam timing: Cam gears are keyed with a light press fit. Chain and tensioner induced variations are no longer a problem.

Load: Eliminating the chains and tensioners eliminates excessive side loading of cam bearings.

Critical sprocket alignment is unnecessary. Use of precision-machined spacers is eliminated.

Performance benefits: This system maintains accurate valve timing when using high performance valve springs with higher spring forces.

Performance fitment: Higher cam lifts can be used without decreasing cam base circle. Gear-driven rear cam rotates in opposite direction from chain-driven cam. Lobes on front and rear cams never point toward each other, allowing increased lobe height.

With the S&S Gear Drive Cam kit and their Pushrod set (which is required), we had all the components to perform the job, including gaskets. All S&S parts are guaranteed for a year to be free of manufacturing defects in materials and workmanship. The pushrod kit even comes with all the covers and O-rings, minus the centers with the springs and washers. We hoped the operation could take place without removing the rocker boxes. If we had to remove the boxes, we would need additional gaskets, not included in the kit.

The reason S&S supplies the covers include the proper length to afford us the ability to adjust the pushrods.

"Gear drives also prevent chain drive drag on a performance engine," Gene pointed out as he started to remove the air cleaner and pipes after the bike cooled.

We had to loosen the exhaust sensor, before removing the pipes. We removed the right footboard and Gene prepared to drop the oil drain plug.

"What's the deal?" he said. "There's still Bonneville salt on the drain plug."


I didn't have an answer and just kept my mouth shut and took notes. Gene pulled the sparkplugs, disconnected the battery and turned the engine over until the rear cylinder pushrods were down, after removing the pushrod cover clips. With bolt cutters he cut the non-adjustable pushrods and tossed them in the trash. Then he turned to the front cylinder. The S&S booklet recommended we jack up the bike securely, put it in 5th gear, and rotate the rear wheel until both lifters and pushrods for either cylinder are at their lowest point on the camshaft (TDC of the compression stroke). Both pushrods for that cylinder will not be under pressure from the valve springs and will rotate with light finger pressure.


Here's a note regarding the adjustable pushrod requirement: 510G camshafts may use stock style non-adjustable pushrods instead of adjustable pushrods. If installing non-adjustable pushrods, disassemble and assemble rocker box per Harley-Davidson instructions. All other S&S gear drive cams require installing adjustable pushrods. As a timesaving measure, the stock pushrods can be removed with bolt cutters. Be sure to heed cautions and warnings: use bolt cutters and not cutoff wheels to prevent debris from entering the engine. Cutting pushrods without releasing the spring pressure (lowest point on the cam) may result in bodily damage or a dead dog, if he's in the way.


Gene at beginning



Hydraulic lifters, guide pin and lifter block.

Gene removed the lifter blocks, which aren't lifter blocks anymore. They are lifter covers that hold a hardened guide pin in place (the pin prevents the lifter from spinning) and seal the area with gaskets and O-rings. Throughout this process, we used a variety of JIMS tools to remove and replace components without risking damage. He removed the cam cover bolts and the cam case cover. It's not necessary to remove any ignition sensor from the cover.



Here's the original Screamin' Eagle cams set in place. There's one chain on this side of the support plate from the pinion shaft to the rear cylinder cam. On the back side a chain runs from one cam to the other.


We used a JIMS tool to hold the cam chain tensioners locked away from the chains after the cam cover was removed. Another JIMS tool held the gears in alignment so we could remove the gear bolts from the cam and pinion shaft. We popped the gears off then the chain tensioners were removed.


Then we moved onto removing the cam set and guide plate all as one piece. The S&S booklet documents specific fastener removal order for the oil pump and cam support plate. The cam system slipped right out of the engine case. In some cases, a press will be necessary to remove the cams and cam bearings from the support plate with a JIMS tool. In this case, the cams and stock bearings slipped right out of the support or alignment plate.



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Another S&S Note: It's not necessary to remove the oil pump from the engine to complete this installation unless grinding in the gear case must be performed for clearancing. If grinding takes place, all gear case components must be removed and all holes taped off with duct tape to avoid contamination.



There's another JIMS tool to support the plate and install the new S&S bearings. Gene used a 1 1/16th socket as a guide to tap the new bearings in place after smearing them with Redline assembly lube. A few light taps and they slipped into place.


S&S supplied a new outer bearing retaining plate and it only slips on one way. S&S recommends checking the clearance between the bearing retainer and the woodruff keys securing inner gears to the cams. Remove material from the retainer as needed to provide .030-inch clearance between keys and retainer. Gene installed the bearing retainer plate and used blue Loctite and tightened the screws to 20-30 inch-pounds torque.


Gene grabbed the new S&S cam set and washed any anti- corrosion packing residue from the surfaces. Then he slipped the correct cam in the correct hole. The longer cam with the keyway is the rear cam. The two cams have alignment notches to indicate how they should be positioned. He used a press to install the cams in the cam plate, pressing the tall cam first until it was even with its mate, then pressed both into place. He double-checked to verify that the cams were aligned properly. Then he coated the crap out of all the new components with Redline lube.


This shot shows the stock roller bearing. The new S&S bearing is a ball bearing set.

He inspected the brass pinion shaft bushing for severe wear and performed a quick test fit to insure that no cam lobes would hit the case casting under the lifters. This wasn't a high performance set of cams, so there wasn't a problem, but it was good to inspect.

It's a lousy photograph, but it is a JIMS tool removing the case cam bearing.

Again he used a series of JIMS expansion tools to remove the case cam bearings. The case cam bearings are the ones known to go to shit at between 10,000-25,000 miles especially under performance loads. The stock bearings are smaller, shorter and fewer in the race than the S&S performance roller sets.


Again a JIMS tools was used to carefully tap the new bearing into the cam gear case. Gene drove the new bearings into the case material until they mated with the inside case lip. While the case was still open, he inspected the oil pump for scoring. He also checked the back of the cam plate where the oil pump rides.

Gene also cleaned the lifter block gasket surfaces while the case was open. Any material that inadvertently fell into the case could be easily removed.

The head of the screwdriver held the oil pump pick-up just the correct distance from the floor of the case.

He installed the cam set and bolts loose and spun the cams to insure there was no binding or problems. He tightened the oil pump Allen fasteners, first alternating sequence, one through four to 95-inch pounds. He performed this task while making sure there was a gap beneath the pick-up opening in the bottom of the pump. If there was no gap, the cam case would fill with oil. He used a large flat-bladed screwdriver as a guide to insure the gap didn't disappear during the tightening process.


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hands installingplate

Then Gene tightened the cam plate to factory torque specs and installed the key and rear drive gear timed with the slots on the components. There's no way to go wrong unless you're blind. He almost forgot the front cylinder cam clip ring that prevents the cam from backing out.


"I never had one come loose," Gene commented.

Gene installed the big cam gear bolt with Loctite and torqued it to 35 foot-pounds. The smaller gear, with washer and Loctite, was torqued to 25 foot-pounds. S&S supplied new fasteners with the gears, but he used the stock machine washers (S&S said you don't need 'em). Next, he replaced the hydraulic lifters.

Before replacing the chromed case cover Gene checked this area for clearance since the S&S pinion gear is larger than the stock unit.

"I always need to think about pushrod order and rotate the engine so the rear valves were down as far as possible,” Gene said. The new adjustable S&S pushrods were just two lengths. The two long ones were used in the exhaust sides.


Replacing the pushrods, tubes, lifter block, guide pin and gasket at one time. A miracle.

S&S supplied all new covers minus the center spring retainers. Gene worked with the lifter blocks and pushrods to determine whether he could install the pushrods without removing the rocker boxes. A larger lift cam could pose a problem; these units were very close to being too long. Gene had to feed the intake pushrod, the lifter block gasket, and the pushrod covers into place in one dainty motion. It was a trick to hold and guide all the elements, but it worked.

There's that surfer in the chrome. He was kind enough to relinquish his trademark pushrod cover containment special tool. Even JIMS doesn't have this one in their stock, just two rubberbands.

I also learned the code of pushrod adjusting.

Gene paints the adjuster flat with H-D touch-up paint and counts four turns, or you can go for 24 flats.

"You lower them all the way," Gene explained. "Then you take all the slack out, and screw them down four turns. The hydraulic lifter doesn't move. You've opened the valve four turns. That's why you can't turn the engine over for ten minutes. If you did the valve could smack the piston. So you need to wait ten minutes for the lifter to settle, and then adjust the front cylinder."

After all was said and done, the pushrods should spin when the engine is turned over and the valves cams lobes are down.

Again Gene checked the cam cover for clearance, since the S&S gear is larger than stock, but we still didn't face any clearance problems. He tightened the pushrod jam nuts on the rear cylinder, checked for spin, then moved onto the front cylinder pushrod adjustment. He waited another ten minutes, checked for pushrod spin, turned the engine over once for a final inspection then replaced the cam cover.

Note:In this case, with new S&S pushrods, the adjuster spins on a fixed threaded shaft, and the jam nuts tighten down against the adjuster and not up against the pushrod.


Gene added three quarts of Redline 20-50 synthetic oil and replaced my Screamin' Eagle exhaust system.

"It should hold four with a new filter," Gene said.


Then I went for a ride.

We dyno'd the King with the new, but very similar, cams. There was no excessive noise and my max torgue came in very close to the original. I'm going to take it back after I put add 100 miles. I'll report back.

This piece was final edited by Bruce Snyder who owns an '03 H-D. He made the following comment about his experience with cam drives:

Here's my shoes after only 12,000 miles. Just out of curiosity, what kind of shape were your tensioner shoes in? Mine were still fully intact at 57K, although the inner shoe would've probably been toast in another couple thousand. But a friend of mine had a shoe grenade and take out the oil pump on his RK at 42K. I can send you a pic of what my shoes looked like if you're curious. Seems to be a crap shoot on how long they'll last - I know another fellow who's racked up over 60K on his '03 Duece with no issues.

Here's Bruce's shoes. Note that all the wear and tear to these puppies could have clogged an oil passage.

Enjoy the ride. My local indy installed Andrews 26Gs in my '03 FXST a year ago (a tad milder than your S&S set) and I love 'em.



Back to Tech

Reader Comments

Page 1 of 5 (17 items)
I loved this article, fascinating. Thank you so much.
I have been looking at upgrading my `03 stock cam plate but spoiled for choice with upgrade cam plates and alike. I really like the idea of gears over chains esp after reading this, but a couple of questions.

A. was the owner happy enough with the stock oil pump?

B. do the pushrods and cam plate have to be removed in order the measure crank run out? As I guess for most people this will dictate chain or gears

reading berkshire, RG, United Kingdom
Wednesday, September 09, 2015
Editor Response Hey, I will also reach out to S&S for more info. I didn't have a problem with the oil pump, but I ran a serious oil cooler. The answer to your second question, I believe, is Yes. But if you are changing out cams and switching to gears, no problem. Here's word from S&S.

When it comes to cams and cam plates and oil pumps, let me say this about that!

You do need to remove that cam plate to check runout on the pinion shaft. A 2003 bike is probably not going to have a problem with run out, but you need to check it. Late model bikes have a much greater chance of having excess runout since the stock spec is currently .012”. Really!

The maximum allowable run out for S&S gear drive cams is .003” When S&S sends out a flywheel assembly the runout specification is .0005” or less, so you know they are going to be fine. The less runout you have, the less problems you will have with vibration and damage to the oil pump and pinion shaft bushing in the cam plate.

In fact, you can make more power with a truer flywheel assembly because you can rev the engine higher!

We recommend removing the oil pump any time cams are replaced because you should replace the scavenge port o-ring. Some guys don’t replace it, but we’ve had enough customers with scavenging problems and the resulting oil pukage after a cam change that we now include the o-ring in our cam installation kits.

That o-ring gets stiff from heat and contact with oil, so it may not seal again if it is disturbed at all, so we recommend that you replace it. Of course it’s a good idea to inspect the oil pump for damage as long as you have the cam chest apart. At the end of the day, as long as you have the oil pump and cam plate out, why not upgrade the both?

Bruce Tessmer | Marketing Projects Coordinator
S&S® Cycle, Inc.

Email bruce@sscycle.com
Great article, guys. Can you recommend an engine builder in my area to do this install?

Kent George
2007 Dyna Low Rider

Kent George
Humble, TX
Sunday, April 12, 2015
Editor Response I will reach out to S&S for you. I'm sure they have a connection near Humble. I knew a guy there named, Johnny Humble. But I wouldn't let him touch my motorcycle.
Nicely done instructional !!

Plastic internal engine parts. REALLY!!! The MoCo could care less who dies on their machines due to poor and inferior designs and DOWNRIGHT NEGLECT. Perfectly evidenced by their refusal to be honestly accountable and incorporate a rear engine brace on the older cruisers, after being told by the designers, that the brace was required.

Death wobble has caused many deaths, injuries and law suit settlements and still the MoCo refuses to admit wrong doing or recall those models to add the $1 part to their machines. Nothing but losers running their MoCo. Every time I touch one of their products, I am reminded of the pure Cr*p and inferior materials they use in the construction of their machines.

Absolutely sickens me, to think of such profound disregard for their customers and others, who continue to suffer injury due to the EXTREME GREED this manufacturer enjoys. Blame that on the Govt too. BS! 30K for a Softee and it's built with plastic engine parts and sold by a sales staff and service staff that's ashamed to even look a customer in the eye, when they're confronted with these countless issues each day.

It is an abomination to God. If all you got was a broken scoot due to the MoCo's pathetic managers, then you have been truly blessed. I hope the lorg will continue to ride shotgun with you. MoCo engineers and executives sure as h*ll won't. You can bet on that.

Pittsburg, MO
Saturday, April 04, 2015
Great article.
I wondered about the pinion runout issue with the MoCo's generous tolerances (re: 2014 pinion runout @ .010").

I've heard that there were runouts reported in excess of .020 found in warranty repairs in bikes with less than 5000 miles. I'm not sure what milage is specified by the MoCo for replacing the tensioner shoes (for me it doesn't matter because I wish to do this mod) but I'm amazed that they didn't provide a tear down under the manufacturer's warranty at the end of the 2 year period. I feel that would have been the responsible thing to do.

I've heard the chain driven design was used to simplify assembly. I think it was so they could use a cheaper press-fit crank to reduce manufacturing costs. Even though it is prone to misaligning itself if the bike is ridden hard, the chain driven cam design is more tolerant of pinion runout issues, where the gear drive design is not, and can still time the engine well enough to get it through its primary 2 year warranty period.

This being said, it makes a lot of sense to consider using an an S&S crank for this modification., if not just for longevity, reliability and the piece of mind- for the added stability of the bottom end for future performance upgrades.

Ted Shredz
Delta, BC, Canada
Sunday, June 01, 2014
Editor Response I think there's a lot of truth in Ted's comment, but we can only
speculate about the reasons that these things happen. However, I can
offer some factual information about S&S flywheels. I've had the issue
where a guy wanted to use S&S gear drive cams, but ended up installing
chain drive cams because his stock flywheels had too much pinion shaft

S&S flywheels will solve that problem, but there are a bunch of
other reasons to invest in S&S flywheels besides the run-out issue.
Here's a link to a YouTube playlist showing some strength comparisons
between stock flywheels, S&S flywheels and stock flywheels with welded
crankpins. The results were pretty amazing even to us!


Bruce Tessmer
Page 1 of 5 (17 items)

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