1973 Honda CB750 Cafe Racer Build Episode 1 – It Begins

Finally!! Back to work on another motorcycle project!

I found this bike last November on Craigslist. The dude I got it from bought it running, took it all apart and started a restoration on it. He bought all kinds of new parts like shocks, fork tubes, seat, oil tank, side covers, all the rubber bits, handle bars, cables, tires, chrome steel rims with stainless steel spokes, wire harness and much more. He also had anything that was painted, black powder coated. ALL of the hardware got a new zinc plating. The head was reworked with a “stage 1” job done by Mike Rieck which cost $500 on it’s own. There’s two front disc brake rotors and calipers and all the hardware for a dual front disc conversion. There’s also a lot of spares including an entire set of carbs! The only thing missing is and exhaust system. He said he had about $2K invested in parts and machine shop labor.
He was between jobs and didn’t have the time or money to finish the project and so he let it go for the bargain basement price of $750.


I’d like to turn this into a nice performance CB750. I won’t be swapping out a whole bunch of parts but I will be improving on what’s already there. First thing to focus on is the engine. It’s partially assembled but I’ll be double checking everything that the previous owner turned any wrenches on. Things like the connecting rods. They should have new bolts in them and not the old ones. They are stretch bolts meant to be used one time.

So, here we go down another path of building adventure. Welcome to another journey!!

Keep on hackin…

How to mat a picture in a frame

Pictures and artwork look great when they are mounted in a frame with a mat placed around them The mat serves to frame the picture better and the colors used can enhance and compliment the artwork. You can take your artwork to a frame shop and have them mount it and cut a mat for OR you can purchase a mat cutting kit and do it yourself.

In this week’s video I’ll show you how easy it is to cut a mat and frame up your artwork.

The photo used in this video was taken by our Friend Brady Beck. He’s a very talented photographer of wildlife and landscapes. You can see more of his work on his website, bradybeckphotography.com

Thanks Brady!

keep on hackin!

DIY Emergency Vehicle Flasher Part 3

I left off last week with a few problems. The second LED array would not go all the way off and after some troubleshooting this week I realized that the circuit was not working properly due to a faulty n-channel MOSFET. This was probably caused by the odd way I was powering up the third 555 in the circuit.

After abandoning the idea of using a small switching transistor to turn on the third 555 an idea hit me. Why not use a p-channel MOSFET? When pin 3 of the first 555 goes low I could utilize the ground signal from that pin to pull the gate of the p-channel MOSFET (Q3) to ground thus turning it on which would allow voltage to flow from the positive rail through the MOSFET to pin 8 of the third 555. I tested it out first on a breadboard and it worked fine so I added it to the schematic and installed it on the perfboard.

The operation of the circuit is as follows. All three 555s are configured as astable oscillators. The first 555 is set to cycle high for .1 to 1 second depending on the position of R2 potentiometer. The positive output from pin 3 goes to the second 555 which powers it up. It then oscillates at approximately 40 21 hz on pin 3 and feeds a positive voltage to the gate of the n-channel MOSFET (Q1) which turns it on and off rapidly thus supplying a ground to the first LED array. When pin 3 goes low on the first 555 the ground signal pulls the gate of the p-channel MOSFET (Q3) to ground and turns it on which feeds a positive voltage to the third 555. This 555 then oscillates a 40 21 hz on pin 3 and feeds a positive voltage to the gate of the second n-channel MOSFET (Q2) which turns it on and off rapidly thus supplying a ground to a second LED array. The result is an alternate rapid flashing of two LED arrays with adjustability in the rate via the R2 20K potentiometer.

This circuit could also drive other lights providing the load does not exceed the amperage rating of the n-channel MOSFETS. It could also be modified to run other devices such as relays or stepper motors. Of course, all of this could be done with a micro controller but I chose the 555 because the design and build of the circuit is a good teaching tool for those wanting to learn beginning electronics.

Below you’ll find a parts list, link to parts suppliers, a PCB layout, the schematic and the final build video.

UPDATE: See Timo’s comment below for an alternative circuit.

Keep on hackin!

Parts list:
2 – 20 ohm 1/4 watt resistors – R8, R9
7 – 1K 1/4 watt resistors – R1, R3, R4, R6, R10, R11, R13
2 – 3K 1/4 watt resistors – R5, R7
1 – 20K 1/4 watt resistor – R12
1 – 20K potentiometer – R2
3 – 0.1 uF ceramic capacitors – C1, C3, C5
2 – 1 uF 25V electrolytic capacitors – C4, C6
1 – 100 uF 25V electrolytic capacitor – C2
2 – N-channel MOSFET transistors – Q1, Q2
1 – P-channel MOSFET transistor – Q3
1 – 1N4004 rectifier diode – D1
1 – 1N4742 xener diode – D2
3 – NE555 timer dip chips – IC1, IC2, IC3
1 – SPST switch – SW1
1 – Knob for the potentiometer
1 – Perfboard or PCB
2 – LED light arrays
1 – Project enclosure
Several feet of 16 gauge two strand wire

Parts suppliers
Tayda Electronics
Allied Electronics
Radio Shack

PCB Layout
Adjustable speed 555 dual alternating light flasher pcb layout

ExpressPCB file
flasher pcb layout.pcb

Adjustable speed 555 dual alternating light flasher schematic

diy 555 flasher circuit board installed

DIY Emergency Vehicle Flasher Part 2

This week I assembled all the parts onto a perfboard after making a layout with ExpressPCB. I use the layout as a guide when assembling circuits on a perfboard. Once the circuit is proven to work I can make a PCB from the layout. In this case it’s only serving as a guide. After assembling the board and connecting all the external wiring and LEDs I tested the board out. I immediately found an error on pin 8 of the first 555 timer. I failed to connect it to the positive voltage rail! OOPS! After connecting pin 8 the circuit began to function but with a minor flaw. The LEDs connected to the drain of the MOSFETs are staying dimly lit between pulsing cycles. They should be out completely! This will require some troubleshooting on my part. The circuit worked perfectly fine on the breadboard. I’ll be double checking my schematic and the circuit and looking for a possible error. It could also be an issue with the capacitance of a breadboard. I’ve run into this type of thing before. Some breadboards act as a capacitor and can influence the behavior of a circuit.

It may be a problem with the way I’ve connected the MOSFET. Here’s is a great beginner’s guide to the MOSFET that helped me understand how they work.

If you have any thoughts on this problem and it’s possible cause please join in on the discussion on YouTube or here on the blog. Below you’ll find a schematic of the circuit, a picture of the circuit on the breadboard and of course this week’s video.

The schematic. You’ll notice that I have a PNP connected to pin 3 of the first 555. It’s actually connected wrong but it somehow works to turn on the third 555! I’m scratchin my head on this one. I’ve revised this several times and this the current circuit. I now have a BC547 NPN transistor serving as a inverting buffer. This works great to turn on the 555 but I still have a problem with the MOSFET connected to that 555. When it’s connected the flashing stops.
555 dual flasher schematic

The breadboarded circuit
555 dual flasher breadboard

Keep on hackin!

DIY Emergency Vehicle Flasher Part 1

I get a lot of email with requests to build circuits for people. Most are more than I would want to take on for a simple Hack A Week project without some monetary compensation but this one was unique. The email tells the story.

“Hey Dino,
I love your site and have a request if you are taking them. I’m member of a small volunteer fire dept. I’ve talked to many members of many fire depts over the years and they are always talking about where to get reasonably priced emergency response lights like Whalen or Code3 makes (they run in the hundreds of dollars from these companies). In our state the lights would be flashing red LED’s.

I think it would be great idea if you could show how to build a relatively inexpensive set of flashing lights (if possible) – even better if they can have variable flash patterns.

We don’t make any money and we don’t receive any equipment for personal vehicles, so being able to make our own would be a great benefit to our cause.

Thanks for taking the time to read this and all the great videos!”

How could I turn that one down? My first thought was to use the venerable 555 timer because it’s readily available and easy to use. Since I wanted two banks of lights to flash alternately I could use two 555s in astable mode and drive one of them with pin 3 when it’s off and goes low to ground. The first 555 would be driven by another 555 in astable mode oscillating at the rate of 1 hz.

Once again I referenced Rob Paisley’s awesome 555 timer page where you’ll find all kinds of info and applications for the 555.

I’ll post the final schematic, a PCB layout and a parts list in part 2 next week.

It all becomes clear in the video.

Keep on hackin!