Technical guru Mark Haycock delves into the mysterious world of ignition systems, and reveals why getting it back to front is sometimes quite OK.

I had a letter recently from one of our readers, Mr A Birch, raising questions about the
workings of an ignition coil so I thought it might be an idea to take a closer look, in particular at
the principle of the ‘wasted spark’.

What we call an ignition coil is actually an example of a so-called induction coil. It is
merely a specialised electrical transformer, the purpose being to greatly increase the voltage
provided by the battery. Despite its name, like any other simple transformer it actually
contains two coils of wire, or windings, one for the low-voltage side (the primary) and the other for the high-voltage (the secondary).

The windings are concentric, and wrapped around a central core made from laminations
(thin sheets) of iron. The core is usually not visible, but in old-style Honda coils it extends
out of the enclosing plastic case (Picture 1). Incidentally, the word ‘voltage’ is sometimes
replaced by ‘tension’ when dealing with ignition coils.

There are considerably more turns in the secondary windings than the primary, and it is
this that leads to the increase in voltage. What causes the output of high tension is a
change in the flow of current through the low-tension windings, with that change traditionally
being brought about by the contact breaker. The aim is to reduce the current to zero as
rapidly as possible. This ‘induces’ a high voltage in the secondary windings, which is fed to the spark plug.
To read the rest of the article,
click the image below to download it as a PDF

Setscew or bolt? Stainless or zinc plate? Technical boffin Mark Haycock gets to grips with screws, bolts and nuts; and advises what you should be using, where and why.

To read the whole article, download the pdf: Screws & Fasteners 101

Setting carb float levels is still considered a black art – but getting it right can make a significant difference to your bike’s economy and performance. Rod Gibson explains all.
So what is a float level, and why does it matter? Deep within the confines of your carburettors lurk a number of jets, whose job it is to draw in fuel, mix it with the air and send it to the engine to be burned. Those jets need to have a readily available reservoir of petrol, so each carb has a chamber fitted at its lower end that is fed with petrol from the fuel tank.
The amount of fuel in the chamber has to be controlled – too much and the surplus fuel will run out of the overflows, too little and the jets will only have air to suck in, and the engine won’t run. So far so simple, but it’s actually a bit more subtle than that, for if there’s insufficient fuel in the float chamber the bike can run weak at full throttle when there’s not enough petrol in the carb to keep up with the demands of the main jet. Conversely, having too much petrol in the chamber can make the bike run rich – but an excess of petrol usually leads to flooding problems.
To read the rest of this article, download the pdf: Setting Carb Float Levels

I have always farmed out wheel re-spoking to a specialist, and since discovering the talents of Paul Jackson (01422 378100) many years ago, have always been more than happy to keep turning up at his workshop, drop my hubs and rims in a pile on the floor (with a note of offsets, of course), and call back a couple of weeks later to collect the shiny results. But having had a go at almost every other aspect of bike spannering over the years, I was aware that actually re-spoking a wheel was scary new territory, and it was about time I had a go.

To read the rest of this article, download the pdf: Re-spoking Wheels PDF

I’ll be posting a whole bunch of these short videos of Fay Butler; metalworker extraordinaire and Massachusetts resident, dropping knowledge and showing you how it’s done. This one is all about laying out a pattern and cutting a blank on some sheet metal. More to come soon.

Our pal cole sent in these pics and a real simple run down of what’s going on with this project he’s kicking around his shop. I dig seeing this stuff in progress, figure you will too. Here’s some notes and pics from Cole…

• Found some junk in my carb (I’ll just put a tank liner in….)
• Might as well shave the left fuel cap….
• I looked in the hole and see that it has a tank liner and it’s peeling badly
• I cut out bottom of tank to scrape out old liner
• While I’m at it, might as well section 2 1/2 inches out the middle of the tank….

Stay tuned for a possible rib down the center of the tank, a hand made tunnel, and a custom made petcock bung at rear of tank!

A typical bike engine contains around three litres of oil, and one of the biggest challenges to engineers over the years has been to keep that oil where it should be.

There are many joints between the various engine castings, and nearly every one needs some means of preventing fluids from escaping. In an ideal world, every joint face would be perfectly flat, smooth and perfectly aligned with its opposite number. Furthermore, when the bolts were tightened no distortion of the joint would take place and they would remain perfectly tightened throughout the life of the bike. Unfortunately, we do not live in an ideal world and this is where gaskets come in.

The aim of a gasket is to provide a little elasticity to absorb the imperfections found at the joint surfaces. Typically, gaskets are made from a mixture of fibres, such as paper or asbestos, held within synthetic rubber such as nitrile. Nowadays asbestos is no longer favoured and more use is made from up-todate materials such as carbon fibre, PTFE and Kevlar.

To read the rest of the article, download the pdf: Motorcycle Gaskets 101 PDF

This latest free ebook - The American Machinist Handbook & Dictionary - is so dense with info, I had to break it into 3 files. This is the 3rd and last installment, the other installments can be found here

Click the link to download: American Machinist Handbook & Dictionary

To learn more about our free ebook series, go here

Part 2

Part 1

This latest free ebook - The American Machinist Handbook & Dictionary - is so dense with info, I had to break it into 3 files. This is the second installment, the other installments can be found here

Click the link to download: American Machinist Handbook & Dictionary

To learn more about our free ebook series, go here

Here’s some basics on milling machines courtesy of the Army Correspondence Course Program.
This is a long one, but if you scratch your head when someone says milling machine, this will give you the START to a basic understanding. Print it out and read it on the can. Make sure to click on read more to get to the whole article.

FIGURE 1. PLAIN MILLING MACHINE-KNEE TYPE.

1. Introduction

Milling machines were first invented and developed by Eli Whitney to mass produce interchangeable musket parts. Although crude, these machines assisted man in maintaining accuracy and uniformity while duplicating parts that could not be manufactured with the use of a file.

Development and improvements of the milling machine and components continued, which resulted in the manufacturing of heavier arbors and high speed steel and carbide cutters. These components allowed the operator to remove metal faster, and with more accuracy, than previous machines. Variations of milling machines were also developed to perform special milling operations. During this era, computerized machines have been developed to alleviate errors and provide better quality in the finished product.

2. Milling Machines

a. General. The milling machine removes metal with a revolving cutting tool called a milling cutter. With various attachments, milling machines can be used for boring, slotting, circular milling dividing, and drilling. This machine can also be used for cutting keyways, racks and gears and for fluting taps and reamers.

b. Types. Milling machines are basically classified as being horizontal or vertical to indicate the axis of the milling machine spindle. These machines are also classified as knee-type, ram-type, manufacturing or bed-type, and planer-type milling machines. Most machines have self-contained electric drive motors, coolant systems, variable spindle speeds, and power-operated table feeds.

(1) Knee-type Milling Machines. Knee-type milling machines are characterized by a vertical adjustable worktable resting on a saddle supported by a knee. The knee is a massive casting that rides vertically on the milling machine column and can be clamped rigidly to the column in a position where the milling head and the milling machine spindle are properly adjusted vertically for operation.

(a) Floor-mounted Plain Horizontal Milling Machine (figure 1 above).
[1] The floor-mounted plain horizontal milling machine’s column contains the drive motor and, gearing and a fixed-position horizontal milling machine spindle. An adjustable overhead arm, containing one or more arbor supports, projects forward from the top of the column. The arm and arbor supports are used to stabilize long arbors, upon which the milling cutters are fixed. The arbor supports can be moved along the overhead arm to support the arbor wherever support is desired. This support will depend on the location of the milling cutter or cutters on the arbor.

[2] The knee of the machine rides up or down the column on a rigid track. A heavy, vertical positioned screw beneath the knee is used for raising and lowering. The saddle rests upon the knee and supports the worktable. The saddle moves in and out on a dovetail to control the crossfeed of the worktable. The worktable traverses to the right or left upon the saddle, feeding the workpiece past the milling cutter. The table may be manually controlled or power fed.

Read more…

Much shorter than yesterdays. More welding vids coming soon.

Grab some popcorn, this one runs 22+ minutes long. Part 1 of 2, I’ll post the next one tomorrow.