106 Inches of Fury, S&S Cycle’s “Baby Stroker” Kit

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106 Inches of Fury, S&S Cycle’s “Baby Stroker” Kit

This story starts like many others I’ve heard while standing behind J&P’s tech counter… “so 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 quickee 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 re-adjusting 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. And 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 and 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 long time 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 its not quite that simple. The flywheel and rod combo that adds the ½” stroke length requires a specific set of 3 ⅞” pistons that have the bottom set of rings actually covering a section of the wristpins. Sounds a bit odd but those boys in Viola no 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 bullet proof 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 Suerstock heads I had scored a while back. I already had the quikee
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 so they all went back into service with the new engine combo.
I after a few heat cycles and a oil change I putted around for about 500 miles over the weekend and did one more oil change. I could not 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 er 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 hit 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 your not ready. The cranking compression ended up being 218psi and is a non issue 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 know “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.

By |2018-12-11T21:05:54+00:00December 11th, 2018|Categories: Bike Builds, Editorial/Commentary Articles, How-To Articles, Tech Tips, V-Twin|Tags: |1 Comment

About the Author:

Patrick Garvin began his stint with J&P Cycles at the start of 2008 after doing some installs for us at Daytona and Sturgis for two years. Currently, Patrick splits his time between the eCommerce team and purchasing, finding new and exciting products for our website and catalog. When he’s not at his desk, he’s zigzagging across the country with J&P’s event crew. Patrick has an obsession with going fast on just about anything, a trait he shares with his 6-year-old son Race. You can usually find both of them wrenching in the garage or ripping through the fields on dirt bikes. Emma, his beautiful wife of 7-plus years, puts up with his antics and keeps his head screwed on because he certainly wouldn’t be able to find it without her.

One Comment

  1. Joe December 12, 2018 at 7:01 am

    Good job Pat ! I actually installed the full S&S 106” Stroker kit ( with the heads and 585G cams ) in my 2003 Heritage Softail in 2005. At the time that I did this work, the EasyStart cams weren’t available yet so I opted for manual compression releases. Fueling oil pump and cam plate and Timken bearing conversion was added to the mix. I shaved the heads .020” and used .030” copper head gaskets to raise compression just a bit more.
    Also, at the time, I was trying different combinations of EFI controllers, exhaust and intake and finally landed on the ThunderMax closed-loop EFI system, Horsepower Inc. 55mm throttle body and D&D Fat Cat exhaust.
    While I, like you, have a very aggressive throttle hand and have a distaste for racing dynos ( zoom, zoom, boom ), I was too curious to know the rear wheel horsepower did a single pass on a local dyno. The TMax had, by now, auto-tuned the MAP to the point of only minor, if any, adjustments so, I didn’t want to hear any “recommendations” for MAP adjustments on the dyno. The end results in my build were: 115.4 HP and 126.2 lb/ft TQ / single pass on 93 Octane pump gas, dosed with an Octane booster ( Turbo104 ) and Champion copper plugs gapped to .036”. So, your “seat of the pants” guesstimate of “110ish” is pretty close.

    TO ANYONE READING THIS WITH A SIMILAR BUILD, RUNNING THE TMAX AUTO-TUNE EFI CONTROLLER: I know, first hand how aggravating it is when none of the available MAPS match your build so, if you are interested in trying my auto-tuned MAP, I will gladly send it to you. Email 106stroker [at] gmail [dot] com and I will reply with the exported MAP file.

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