Bikernet Blog Search Bikernet
Ride Forever -
Monday Edition

5-Ball Racing, Bonneville 2010, Part 7

Bonne Belle Engine Engine Work and Transmission Dilemma

By Bandit and the Departure Bike Works Crew
6/11/2010 2:12:41 PM

Share this story:


Bonne Belle Update

Another 5-Ball effort made progress. The 1940 WLD flathead, at Departure Bike Works in Richmond, Virginia witnessed true progress. Hidden in an Ozark Cave, until recently, were etched stones containing flathead speed secrets. Lee Clemens, the Boss of Departure, knows all who know anything about engines and performance. He had a distant drawn-and- quartered connection and came in contact with these highly secret tablets. The mystery continues

45 case

I’ll try to innumerate several of the 45 cubic-inch, side valve performance suggestions. Originally we discussed dual front cylinders for dual carbs and better air flow. There’s a problem with that recipe. First we found that K-Model top ends flow even better than dual carbs. Plus trying to find and possibly breaking up two sets of rare WLDR top ends wasn’t a friendly formula and a tough menu to follow.

45 case drive side

That’s not all. Jim Lienweber would be forced to grind some very exotic cams for the dual-carb job, whereas a clean set of WLDR cams fit the golden formula for 45 speed.

front with stud sticking out

45 bore without baffle

There’s a baffle in one of the cylinders to create just the right mixture of oil to enter the cylinder under the piston of a stock 45. In the above case, part of our speed mixture, called for baffle removal to allow the piston to scream up and down the cylinder unhampered. Backing up that modification called for machining the breather gear in the cam case to create the ideal vacuum, let the motor breathe and the air evacuate. This also forced Ross pistons to deliver three piece oil rings over the stock one piece jobs.

stud replaced at front

In order to mount the K-Model top end, the precursor to the Sportster, a stud needed to be moved. Flatheads have four square studs, like at the corners of a square box. Sportsters and K-models come with one stud, slightly out of wack. It forced Lee to machine aluminum studs, run them into one cylinder mounting, case stud hole, slice it off and re-face the surface.

That’s not all. The cylinders needed to be measured from the crankpin up so that the head lands on the cylinders were perfectly square and the same between the cylinders for exact compression.

faced rearclose

That’s not all. Lee needed to check the face of the heads and make them absolutely square with the top of the cylinders.

standard cylinder

Lee discovered that there was a difference in the thickness of the heads from the valve side to the combustion side. He made a fixture to hold the heads perfectly square (upside down) so he could machine the correction into the mating surface between the aluminum heads and the iron cylinder head gasket surface. It took him a while to discover all headbolt surfaces are not created equal. He was forced to study the distances from the head gasket area to the headbolt washer landing to determine how to create the ideal fixture. He burned through another day in the shop trying to create the Worlds Fastest 45 Flathead.

mod cylindertext

That’s not all. Skeeter Todd dropped into Departure Bike Works to discuss all that’s performance in the kingdom of Harleys and the conversation shifted to the Bonne Belle. “What transmission are you going to use,” Skeeter said. Skeeter is like a monk from the flathead piston tribe in the Catskill Mountains. When he asks a question—he knows the answer.

“The stock 1940 three-speed with a tall rear sprocket,” Lee timidly muttered, knowing he was about to have his ass handed to him.

"With a stock 3-speed you will fall off the cam in third gear, and struggle through miles trying to retrieve the needed rpms to reached the peak power curve," Skeeter pointed out graciously. The stock transmission was out. Lee has a connection for wrecked bikes through insurance companies and volunteered to cut a 5-speed transmission off a late-model Sportster and ship it to the other coast. “One problem,” he said. We need to seal up the case and develop a means to fill it with oil.”

Seems S&S makes a trap door with an oil fill hole and sealed bearings. Then it’s up to me to form the welded transmission case and mount it in the exact location from the engine drive sprocket as a Sportster, so we can run a Sportster designed belt system. We will also run the late model Sportster clutch, another beneficial project.

gregssporty cases

I immediately called Greg Friend, the former Street Chopper editor, who now the marketing director of Saddleman Seats. He cut a Sportster transmission free from the case to build a split Sportster custom. “Ah, I sold the transmission at a swap meet,” Greg said. “I’m using a Baker big twin transmission.”

I couldn’t believe my ears. See the image above. We shifted gears, found a transmission, cut it free from the Sportster engine cases, but it would not fit the 45 frame. We contacted Fat Bob and he recommended an old Triumph 4-speed. We started moving in that direction until Paughco announced they're new 45 frame designed to house a big twin 4-speed or Softail 5-speed transmission. That called for a team meeting. Hang on.

rear cylinder with plug

DBW banner

Share this story:

Back to 2010 Bonneville Effort, 5-Ball Bonneville Racing

Reader Comments

Like this article. Would love to see more

Eric Kahn
Miami, FL
Wednesday, February 20, 2013
Editor Response We will start a whole new Bonneville effort in the very near future. Ray writes about his 124-inch every week in the news. I'll bug him about another feature.

Your thoughts on this article

Your Name
Anti-Spam Question:
Please enter the words you see in the box, in order and separated by a space. Doing so helps prevent automated programs from abusing this service.