106″ Of Fury: S&S Cycle’s Baby Stroker Kit

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Article And Photos By: Patrick Garvin

Originally Published In The May 2018 Issue Of Cycle Source Magazine

This story starts like many others I’ve heard while standing behind J&P’s tech counter… “I was just driving along….” So, there I was, just cruising along on my trusty Dyna (and by cruising I mean thrashing it per usual) and I swear I hear a ticking sound. I can’t quite place it, but it sounds like lifter noise to me. Of all the bikes I own and have ever owned for that matter, this 2003 Dyna is the most stock I have ever kept a motor. Around 10,000 miles ago I replaced the failing cam chain tensioners, and aside from the S&S quickie pushrods, the internals of the engine were completely stock. So, I was a little bewildered at the noises coming from my bike. Despite my general protocols of hot rodding  everything, this little Twin Cam 88 had been extremely bulletproof considering my overzealous throttle hand. The only thing I could figure was that maybe the pushrods needed adjusted, so I popped off the covers and went through the process of readjusting all the pushrods, and low and behold… still a ticking noise, and it seemed to be getting worse. At this point, it was time to start taking parts off until I found the culprit. It didn’t take too long to find. I pulled the cams and cam plate, flipped it over to inspect the cam chain tensioner when I noticed a rather glaring problem. The oil passage around where the output shaft comes through the plate was cracked! About a half a second later I realized I had scissored my flywheels. I’d seen a number of scissored Twin Cam flywheels but had never experienced them getting so out of whack and wobbling the output shaft bad enough to crack the cam plate. I was intrigued, so I set up the dial indicator and gave it a spin, the needle jumped over to 47 thousandths! I thought maybe the dial indicator wasn’t zeroed or perhaps it moved. I reset everything, and again it read 47 thousandths. Just to put this in perspective, S&S requires less than 3 thousandths for gear drive cams and HD spec is 12 thousandths, I had managed a rather catastrophic 47 thousandths. I’m not gonna lie; I was kind of impressed with myself. While admiring my handiwork, I was a little bummed about my broken motorbike but also stoked that I was finally gonna build the motor.

Junk flywheels meant a complete teardown, splitting cases for a fresh ground up build. Which meant the possibilities were endless as far as I was concerned. I had picked up a set of 79cc S&S Superstock heads a while back that I had been keeping for such an occasion but other than that I really had no direction for the build. The ends of the displacement spectrum for me were 95 – 124 inches. At the very least I was going to do a big bore (95”), but I considered it a waste to put a stock stroke flywheel back in there. On the other hand, did I really want to go as radical as a 124? After some time of pondering, digging through the interwebs and doing a fair amount of bench racing, my buddy and longtime S&S staffer Dean Young suggested a lesser known 106” S&S kit. I like the idea of the 106 that was more than your standard big bore but not as radical as the mega stroker, big bore 124 kit. To get to 106 cubic inches with a Twin Cam 88 you basically put a ½” stroke on a 95” kit, but it’s not quite that simple. The flywheel and rod combo that adds the ½” stroke length requires a specific set of 3 ?” pistons that have the bottom set of rings actually covering a section of the wristpins. Sounds a bit odd but those boys in Viola know their stuff, so who am I to question it.

I cracked the cases on my trusty Twin Cam and emptied the stock flywheel and rod combo that basically was as useful as a boat anchor now. While the cases were apart, it would have been ignorant of me not to do Timken conversion to keep the new hot rod set up as bulletproof as possible. Under the watchful eyes of Dean and Tom Smith I had the new bearing set up in and the new flywheels in and buttoned up. I knew I wanted to go with a bit of an aggressive cam and so I decided on the higher compression piston option and used the 11:1 compression set of slugs. With the cylinders bored and new pistons nestled in their new homes I capped them off with the set of S&S Superstock heads I had scored a while back. I already had the quickie pushrods from the cam chain replacement from the previous year, so I mated them to some S&S premium lifters with the HLT kit, another measure to keep me from trashing stuff. I personally really dig “back half” style cams. I like the feeling of riding the ramp of the cam when that power band hits, and it feels like someone kicks you in the back. I decided on the S&S .585 Easy Starts. With my displacement and bump in compression I would have ample torque down low and a screamer at the top of the RPM range. And the Easy Start feature would eliminate any hard-starting issues due to the  increased compression. With the new dead nuts S&S flywheel (all the S&S flywheels are within a ½ a thousandth runout) I used a gear drive set up and of course capped it off with the blue S&S cam plate and oil pump (the blue adds 2 hp). I took the opportunity while everything was apart to powder coat all my chrome covers an HD wrinkle silver color and popped the mill back in the bike. I already had a Twin Tec ignition, Mikuni HSR42 and a Bassani Road Rage III, so they all went back into service with the new engine combo.

I after a few heat cycles and an oil change I putted around for about 500 miles over the weekend and did one more oil change. I couldn’t wait to get back out of the garage after oil change number two. I cleared my driveway and rolled up into second gear and gave her the beans. It stretched my arms, and the front wheel skimmed across the pavement as I grabbed third with a with a giant cheesy grin on my face. I took a left turn at the stop sign and slammed it wide open in first, and it yanked the wheel about two feet off the ground as I banged second gear just before I hit the rev limiter. I was ecstatic, you don’t always know how motor combos are going to work out, but this one couldn’t feel better to me. It was pretty docile down low and just cruising through town, but when you twist the throttle, it hit like a hammer. When the tach sweeps past 2800 RPM, it unleashes the beast and will put you in the back seat if you’re not ready. The cranking compression ended up being 218psi and is a nonissue when it comes to starting due to the Easy Start cams, with good gas and the ability to control timing with the Twin Tec unit I’ve had no pinging issues. After about 5000 miles I’m extremely happy with the combination. I’m not much for racing dyno’s, but I am curious to know what the bike is making for horsepower. Seat of the pants tells me 110ish but do think it would benefit from a larger carb; I may move up from the 42mm Mikuni to the 45mm to see how it runs. Overall, I spent about $3300 not including the parts I already had, and I definitely got my money’s worth. The lesser known “Baby Stroker” 106” kit from S&S is a clear winner in my book. If you’re looking for reliable power over 100” for your Twin Cam 88 powered machine, this is a can’t miss option.

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