Eric made quick work of getting the engine ready for its new components.
Stock H-D head castings are the castings Rosa’s works with most frequently. They are well made, present the machinist plenty of material to work with, and most importantly, they are plentiful. When heads arrive at the shop, Rosa’s disassembles the stock heads and then mounts the castings in its five-axis Millport machine. They then pick the CNC program (Rosa’s had its own designs digitized) for that engine configuration and let ’er rip. The Millport does what took quite a bit of time to do by hand and it does a great job, over and over again, perfectly and consistently.
Once the head comes off the Millport, the combustion chamber is polished by hand, guides installed, and the valve seats are cut at the Serdi machining station. There is a process involved in cutting the seats and then checking each valve’s seal, it’s not a set-it-and-forget-it machining process, the operator needs skill in knowing just how much pressure to apply to the cutting head—hamfists need not apply. Once the heads have been fully machined, they are CC’d with a burette and mineral spirits to ensure they are consistent to each other and hold the correct volume and then the whole shebang is reassembled using new valves, springs, and keepers. There is a lot of work that goes into a set of custom flowed and ported heads, as you can see.
With one person (Andrew), taking the cylinders and heads through each of the machining, cleaning, and reassembly stages, it ensures that each and every detail has been attended to. There are many steps that need to be taken into account to make sure the job is done correctly, and no corners cut.
Over in the service side of the shop we caught up with Eric (Rosa’s tech) and the Street Glide that had been brought in to get a bump in displacement. Eric handled disassembly and it was a no-muss affair, one of the benefits of working on a new machine. The exhaust was the most tedious piece to remove (as to be expected). All of the pieces and parts were carefully stowed for reassembly; a minute invested in being organized pays dividends down the line.
With the heads and cylinders handed off to Andrew for machining, Eric got busy removing the stock cams and swapping them for a set of chain driven Andrews TW-54 cams. Once the cams were installed, he went around to the other side of the bike and installed an AIM lockup clutch to keep spring/hand pressure modest, while providing the gripping power that will be required when the owner twists the throttle with spirit.
Neatness counts, and makes life a lot easier.
The AIM VP92T lockup clutch will help get a grip on the clutch while also easing the grip
A marriage made in heaven, the brand-new CP piston getting fitted with its rings.
When he was finished machining, Andrew gave the cylinders and heads to Eric who had already installed a set of CP 107FT pistons on the connecting rods. Eric placed a fresh O-ring on the bottom of the cylinder and carefully installed the cylinder over the gorgeous piston; a fresh Cometic gasket went on top of the cylinder and next up was installing the head.
Cometic gaskets ensure a tight seal.
Using a maintained and calibrated torque wrench is the sign of a pro and Eric had his pricey pride and joy in his hands, making sure the adhesive force holding the cylinder and heads in place was sufficient and up to spec. Then with the heads on and torqued, he began the chore of reinstalling the intake and exhaust system. In many instances the customer’s desire to squeak out the most power out of his/her engine as possible, (no matter cost) dictates the use of one of Rosa’s custom throttle bodies, but in this case, budget and needs didn’t require it, so Eric bolted the stock unit (sufficient by most any measure) back on the machine. When putting the rockers back on, Eric reminded us to make sure to replace the all important sealing O-ring with a new one.
With everything bolted together, cleaned up, and wiped down, the bike was then wheeled into Rosa’s Dyno Hut for its inaugural run in the world of triple-digit displacement. Andrew downloaded the TehnoResearch maps to the ECM and pressed the Start button. We don’t care how many times you’ve heard a new engine fire, but it brings a smile to everyone’s face no matter how salty or green they are.
With the selected map in place the bike was run through its paces and tuned. A few short pulls later, the machine rolled off the dyno with some very healthy and respectable numbers. In its stock trim the 96ci engine made 68.7 hp and 85.4 lb-ft of torque. After the Rosa’s 107ci upgrade and with a set of Rinehart True Duals the Street Glide produced 111.1 hp and 120.1 lb-ft of torque. That equates to a 61.72 percent gain in hp and a 40.63 increase in torque. The bike sounds like a beast, its tractive power is so much more dramatic, new life has been breathed into this machine, upping the fun quotient by a factor of 10x.
If you are considering adding some spice to your 96ci TC, give the 107 configuration as described here consideration; it’s a proven winning combo that has given many folks smiles for miles! B
Eric applying just the right amount of torque to the heads.
Rosa’s offers throttle body options, but for this bike the owner decided to stick with his
Missing a minor but important detail like the sealing O-ring can be bad news.
Into the hut, the dyno hut.
The results speak for themselves. The 107 install was a great success that netted a gain o
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Rosa’s Motorcycle Shop