Operation: Texas Thunder

Check out our new stuff on the right. Between the D&M Custom Cycles air cleaner, Lifestyle's special grind cam (not shown), and Mikuni 45mm carb, our 107-inch S&S motor was about to gain both performance and style.

The new Medustas pipes from Martin Brothers (top) are also a pretty big departure from the stock A.I. exhaust.

Lindfors started by taking off the tank so he could access the top of the motor without any interference. He also removed the spark plugs and their wires.

Lindfors went on to remove the ignition switch housing, then he unbolted the top motor mount.

Our S&S has electronic compression releases. We disconnected their wiring so we could remove the heads.

The air cleaner came off next, then Lindfors backed the throttle cable adjusters off before unbolting the carburetor.

Lindfors removed the pipes, then got started on the motor itself. He unbolted the rocker box covers first, then the rocker arm assembly, making sure both valves were completely closed. He pulled the pushrods out at this point and set them aside in the exact same order they were removed, so they would be installed correctly later. He also kept track of the rocker assembly bolts by putting them back in the assembly once it was taken off the bike.

Before we took off the heads, we unbolted the intake manifold, then Lindfors removed the pushrods.

Check out this neat trick for removing cylinders and pistons. Rather than taking them out as separate units and having to mess with fitting the piston rings during reassembly, Lindfors pulled up the cylinder just enough to reveal the wrist pin that held the piston to the connecting rod. Then, he removed the pin keeper and tapped out the wrist pin enough to clear the connecting rod so he could lift cylinder and piston off as one and set them aside for later. Once that was done, he took off the lifter blocks...

...and moved down low to get started on the cam. He liberated the ignition cover, the ignition pick up, and the cam cover itself before he pulled the camshaft.

Lindfors turned the heads over to Larry Hardy, Lifestyle's Performance Techniques motor expert, for porting. For a street bike like this one, you don't want the largest possible ports or you'll actually lose performance in the 2,000-4,000rpm range, where most of us do our street riding; wide-open ports are best for drag bikes. In the 2,000-4,000 range, port shape determines the velocity of the mixture and exhaust flow in to and out of the combustion chamber. The idea here is to increase airflow, shaping the air so it goes in faster, pulling fuel in quicker, and then sending the exhaust out without it backing up in the chamber.

Hardy had to make a baseline test on the flow bench to measure our starting point. He prepped the heads by replacing the valve springs with lighter ones for testing only; he put ours back on after all was said and done. The lighter springs keep the valves in place and make it easier to regulate airflow through the ports during testing.

A venturi simulator went onto the head to give us the basic shape of an intake manifold sending mixture into the combustion chamber. When it was time to test the exhaust port, he'd attach an 8-inch length of pipe to simulate an exhaust system.

Hardy used the state-of-the-art Super Flow SF-600 flow bench to make the initial test on the intake side at 25 inches of water pressure, so that any turbulence or obstructions would be detected in addition to giving us our flow data.

After that first test, he sandblasted the combustion chambers and got down to porting. The porting process is as much an art as it is a science. Porting guys learn their technique over time, like an artist learns how to use a brush. They also use flow bench data and dyno testing to check their work. Hardy used a rotary file to make a rough cut, then used a finer stone to smooth it out, and an even finer stone beyond that. He also took care to smooth out the walls and ridges leading into the combustion chamber for more efficient flow. After the porting was done, he sandblasted the ports to create turbulence and better fuel atomization.

A blast of air followed by some brake cleaner cleared out the ports. Then, it was back to the flow bench for our new data. Hardy would go back and forth between the testing and porting until he had what he felt was optimal velocity for our needs.

To keep the heads at proper compression, Hardy surfaced them with a milling machine.

When Lindfors got the heads back from Hardy, we couldn't wait to see how the bike would do on the dyno, so he plunged right into putting the motor back together. He replaced the base gaskets, then slid the rear cylinder and piston over its connecting rod, installed the wrist pin, and gently brought the cylinder to rest on its gasket.

Working our way up, Lindfors changed the head gaskets and bolted the heads on over the cylinders. He torqued the bolts down in a set pattern in multiple steps so the head would compress evenly onto the gasket and cylinder, and we wouldn't have any leaks.

On the right is Lifestyle's own special grind cam just for the S&S 107-incher in the Texas Chopper. The new cam has larger lobes that will keep our valves open long enough to get all that extra fuel and air in and out of the combustion chamber.

Before installing the Lifestyle cam, Lindfors pre-measured the length of both cams with a caliper and used the difference of 0.001 inch as a starting point for determining endplay, or if we'd need a shim. The difference was too small to have an impact, so no shim was necessary.

Lindfors pushed the camshaft assembly back into the cam chest, taking care to align the timing marks on the cam, breather, and pinion gear. He put some assembly lube on the cam to protect it until oil pressure built in the motor. If you used a shim, you'd want to use a feeler gauge to verify endplay at this point, but for us, that wasn't necessary, so he moved into putting on the new cam cover gasket and reinstalled the cover.

Okay, back up top to button things up. The lower and middle parts of the rocker assembly went on per the owner's manual, but our new Pro-One pushrod covers have a unique design requiring special installation.

You can't adjust the pushrods with the Pro-One covers on them, so Lindfors had to reassemble most of the motor without the covers, adjust the pushrods, then take off the rocker assembly and pull the adjusted pushrods out to install the pushrod covers. However, the tubes clean up the motor, making it worth the extra effort.

Our modified mill was coming together smoothly, and at this point, we were ready to add an intake system. Lindfors installed the new manifold, then installed the polished Mikuni carb.

The D&M air cleaner assembly was joined to the carb by way of an included adapter. Lindfors likes to live dangerously, so he aimed the pointy air cleaner straight up. If the new sound and big power don't get the motor noticed, the air cleaner sure will.

We had a way to get more mixture into the motor at a higher velocity. We still needed a better spark to ignite it and for that Lindfors turned to Daytona Twin Tec for a new ignition. He bolted it to the cam cover, installed the ignition cover over it, and finally routed the wiring to the electrical system. But after torching the mixture, what about getting the exhaust out of the motor?

Martin Brothers' Medustas exhaust answered that call. Their crazy bends go great with the wild look Lindfors was creating for this bike.

The Joker Machine rocker boxes and ignition cover arrived a few days after we put the bike back together. They looked so good, we went back and installed them on the motor just like the old ones.

After the Texas Chopper was back together, it went back on the dyno and the gains were impressive. It originally made 104.5 lb-ft of torque and 91.2 hp but all of our changes ran that up to 121.3 lb-ft and 116.5 ponies. That's almost 20 percent more torque and over 25 percent more horsepower.

The A.I.'s motor looked good stock, but after Lifestyle made the changes, it had a new identity and a lot more power to go with it. Check back with us next month when we dress up the driveline.