Tuning the Bobber

It's been 3 months since final assembly of the bobber. In my schedule I gave myself  some time to fine tune everything before final paint and powder coat, and I'm sure glad I did. Since August I've done more tuning and motor work that I ever thought; tearing into the top end, going through the ENTIRE charging system one wire at a time, and replacing nearly every gasket, o-ring, and rubber part on the engine. The good news is each change gets me one step closer to a well tuned machine.

The latest change was to replace the aftermarket "pod" air filters with the stock air box. I've learned the hard way these carbs do not operate well with the turbulent air flow pods provide. Unfortunately, the stock air box is massive, and required some cutting of my custom frame to make fit. Here's the air box all hooked up.

Now the only aftermarket piece of the engine is my exhaust. It's a Kerker 4 into 1 header with the muffler removed. I did the "lollipop" trick to try and retain some back pressure. The "lollipop" is a washer welded to a bolt and acts as an orifice plate...here's a picture of it near the end of the exhaust.

The guys at cb750c.com have been a huge help this entire process. Here's a video I shot using the bar camera mount to give them a listen after these changes were made. I tried to open her up as much as I could, but the Houston streets only allow for so much of that, especially with a hardtail...I swear I caught air at least twice on this ride. The bike sounds great and pulls hard, but still not perfect enough for me...hopefully soon!

Variable Speed Drill Press

I recently made the decision to get a drill press...the cordless drill and my wrist were tired of waiting for a mill. A few days searching on craigslist, and using an old treadmill motor I had laying around, got me an inexpensive and useful tool for the garage.

The drill press was made by Orbit. It's an old Taiwan press that I've read is much better than the chinese ones floating around. The owner wanted $230 for it, but we worked a deal where he kept the motor and I got the press for $50. It also came with a 1/8" - 5/8" Jacobs chuck with a #2 Morse Taper...great American made chuck that will fit the lathe too. First thing I did was strip it down for a closer look.

I was very impressed with the inner workings; well made and everything was still nice and tight. While I was inspecting it, all moving parts got a fresh coat of lithium grease.

To fit my motor I needed to make some modifications to the belt and pulley housing. I used a funnel to trace a circle and enlarge the hole.

I also had to modify the switch plate. The original had 2 switches: one for the motor and one for a working light. I'm not using the working light, but did need a place to mount the speed control knob. I picked up a metal cover plate from Home Depot for a blank canvas.

Some dremel and file work and I had a new switch cover.

The motor is a 1hp treadmill motor I got from an estate sale almost a year ago. The treadmill was broken, so I was able to pick it up for $5! I utilized the orignial motor mount as a welding jig for my new mount.

Here's how the motor is mounted now.

For my first design I tried to use the existing v-belts and build spacers to get the motor located correctly. Here's some spacer work on the South Bend.

And here's how it looked with the spacers installed. Unfortunately, the flywheel on the motor was just too large. So eventually the spacers came out and I was forced to by a new v-belt for $10.

I mounted the electronic controller below the motor to take advantage of the cooling fan. I also made a wood cover to protect the circuit board.

Time to wire everything up. Luckily it went together just fine and I had all the correct connectors to make it work.

The wiring and entire assembly cleaned up very nice.

Here's a picture of the switch cover mounted. I also machined an aluminum knob for the speed control.

All done! For $65 I'm very happy. With the money saved I'll be able to get a clamping set and start saving for nice vise.