Return to Library Contents
by Bill Whalen, BSAOC
Reprinted from the Chicago N.O.C. Mar-Apr Newsletter
On the BSA Clubs recent North Coast ride, a problem came up with the electronic ignition installed on one of the Nortons that invariably tag along with us BSA riders. It seems that the Norton ran fine until we pulled into the motel parking lot in Fort Bragg, where it died and refused to start again. About fourteen of us helpful BSA Club members proceeded to shove the rider out of the way and try to troubleshoot the problem for him. Two things were immediately obvious: first, fourteen people cannot work on the same bike at the same time, and second, everyone had a different opinion of what the problem might be and how to proceed. To make a -long story short, we finally reached a consensus that the Boyer electronic unit was faulty and we needed a replacement.
After several calls to the Bay Area, a new unit was located, in, of all places, a Ducati dealership in Ukiah. The only problem was that it was a BSA-Triumph unit. This sparked a new debate among the enlightened: Would a black box from a BSA-Triumph unit work on a Norton? After much discussion and several phone calls, which I understand reached all over the country, the answer game back that, yes, you can substitute the Mark III BSA unit for the one fitted to the Norton. Why, then, do they market the Norton unit separately from the BSA-Triumph unit? Also, why do some BSA-Triumph units turn on with the ignition switch and stay. on, while Norton units not come on until triggered, and then turn back off? Is there a difference in the advance curve?
These questions point out one of the only problems that I have found with electronic ignition systems. They are generally .so reliable that once they are correctly installed, we tend to just forget about them, and since their failure rate is so low, we dont get much experience troubleshooting them. In addition, there doesnt seem to be much information available on how to test than if we suspect they may be causing problems.
Well I decided that I would attempt to correct this problem, if possible who better to answer these questions, I thought, than the folks at Boyer? I have talked to them several times over my many years of using Boyar ignition units, and have always found them to be very helpful and friendly, especially when they know that you are knowledgeable in electronics and are interested in their products.
In order not to waste their on the Norton (kickback), the time and my money, I decided to make a list of questions that I would like to have answered. I called the Boyer Company early one morning, As luck would have it, the person who answered the phone was just the person I needed to talk to, a very knowledgeable and helpful Ernie Bransden. Here are the answers to some of our questions, with a little history to boot.
The Boyer Bransden Co. is a small concern supplying ignition systems not only for motorcycles, but for all sorts of pumps, motors, lawnmowers, etc. Yes, indeed, there were Mark I and Mark II Boyers beginning back in the late 60s. The Mark I was the first model, and was fitted to racing Triumphs in the late 60's. It was considerably bigger than the present units, the black box being about 4" by 5".
Then came the Mark 11 unit, which must have been very small and compact, as the whole unit fit inside the points housing of a Triumph. This approach was dropped, possibly because of heat and stability problems, and the Mark III unit was the result. I have personally never seen either a Mark I or a Mark 11 unit. Since becoming a convert to electronic ignition about ten years ago, all my experience has been with the Mark III units, of which there have been several versions.
Ernie informed me that the early Mark III units were different for the Norton. Because of starting problems on the Norton (kickback), the current to the coils remained off until it was turned on by a trigger from the pulser coils when the engine was turned over. It would then turn back off in a second or two if no further pulses were received.
The BSA-Triumph unit, on the other hand, had current to the coils as soon as the ignition switch was turned on. The later Micro Mark III units are all the same; they remain off until triggered on, and then they will turn back off in a second or two if no further pulses are received. This is what they call a "soft turn off": it doesn't produce a spark at the plugs, it just turns off the current to the coils. A good idea, if the key were left on. All of the Boyer units produced in the last few years are of this type.
All units have the same basic-advance curve, which is controlled by the trigger pulses. I'm not going to get into the theory of how the advance is produced, but you will notice when you put a strobe light on the bike during installation of your Boyer that the unit keeps on advancing with increasing RPM, unlike the mechanical advance unit you are replacing. The mechanical advance unit has reached its full advance by about 3000 RPM, whereas you time the Boyer at 5000 RPM. This is not a problem, only a difference between the two systems and how the advance is produced. And remember, that mechanical advance unit was the Achilles' heel of many a British bike.
Now that we know a little more about how they work, we can talk about how to check them out if we suspect they may be faulty. The first thing you must do is to forget about what's inside the little black box. It doesn't matter. That little black box does only two things: it turns the current to the coils on and off, just the same as the points did in your old system, and it provides spark advance. That's it's only job. If it stops doing that, it's bad.
Remember back when I said that once correctly installed, they generally work fine? Well, most of the time when someone has trouble with his electronic ignition, it goes something like this.
"I dunno wha happend, it just quit. I wus reel curful when I put tha sucker in! I twisted ever wire, and even double wrapped it wit lectricians tape, and I smashed ever connecter wit my hammer!"
No, that's not what I meant when I said correctly installed! Most of the problems I have encountered with Boyer units have been the result of bad connections. Every connector must be clean and tight, and even though the spade connectors that come with the unit are pretty good, after I crimp them on with the proper crimping tool, I solder them just to be sure. Remember, every connection is critical, even the ground connections. So, what I'm suggesting is that if you encounter problems, first, take a good look at all of the connections to make sure they are still in place. Let's take a look at the schematic of a typical positive-ground installation.
Notice that there are only five little wires going into the Boyer unit; two, BM and BN, are used for the trigger circuit, white is the 12v supply, red is ground, and the black is the switched 12v to the coils. Pretty simple, huh? But take another look at the white lead. The power in the white lead goes through 11 different connections getting from the ground side of the battery to the Boyer! It must also be capable of carrying between 3 and 4 amps of current! A bad cell in your battery or a bad connection anywhere along this path can cause you problems.
In order to understand why a bad connector has such an adverse effect on the circuit, again take a look at the schematic. Notice that the only resistance in the path from ground through the coils, the black box, the kill switch, and the ignition switch to the battery, is the resistance of the coils themselves. Each 6v coil has only about 1.5 to 2 OHMS, so the total resistance should be 3 to 4 OHMS. Remembering that I=E/R, this is where we come up with 3 to 4 amps. Put a few extra OHMS in there and you can see what happens. That is the reason that all the connectors must be in good condition.
Enough about connectors, I'm sure you got the point by now. Let's get on with some troubleshooting.
Again looking at the schematic, we can break it down. to four basic sources of trouble. (1) The black box itself, (2).The 12v supply to the box, (3) The coils and plugs, and (4) The triggering circuit. Here are some trouble shooting hints recommended by Bayer that may help isolate a problem.
Simple tests on Bayer Mark III Ignition Units for British Motorcycles.
1. Switching on the ignition switch and turning the engine over should produce a current through the coils, (a voltage at point (3)). No current through the coils could be caused by:
* No voltage to the white wire at point (2). (Battery voltage low, less than 9 volts.)
* Bad connections, anywhere in circuit.
* No earth to red wire at point (4).
* Coils or link wire between coils open.
* Black wire shorting to ground, or one of the coils shorting internally. Black box very hot.
2. Wires can rub through to frame. Check for any shorted wires.
3. All battery cells should be in good condition, as a poor cell will produce a high resistance in the 12v supply to the ignition unit. A bad battery cell can cause the ignition to produce a spark on switching the lights on or using the horn. A bad battery cell can also cause a continuous stream of sparks to occur.
4. A simple test of the transistor box can be made with the box still in the I circuit by disconnecting the yellow/black and the white/black wires at (5) and (6), and with the ignition on they can be touched together and broken. This should produce a spark at the plugs. If it does not, the box is faulty.
These are some pretty good suggestions, but I would add a couple of my own gained through my own experiences. The first thing I do if I suspect I have a problem with my electronic ignition system is to either pull one of the spark plugs or one of the plug leads and connect it to a spare plug. I hold the plug against the head while someone else turns the engine over. I should see a spark at the plug. If not, I need to isolate the problem further.
Luckily, you don't need any fancy tools or equipment to troubleshoot your ignition system. You can do a lot with just a piece of wire and a 12v bulb. If I had a Volt/Ohm Meter things would be simple, but let's assume that I left my meter at home. I usually carry one of those little 12v test lights with me, but you can also use any 12v bulb and a piece of wire.
A simple way to eliminate all the wiring, switches and connectors in the 12v feed to the box is to take a piece of wire and connect it between the (-) negative side of the battery (1), and the white lead to the box at (2). This will eliminate the ignition switch, the kill switch and any other connectors in this line. If this solves your problem, and you now have a spark when the engine is turned over, you have a bad ignition switch, a bad kill switch or (what else?) a bad connection!
With this same piece of wire, you can test your coils and plugs. Simply disconnect the black wire from the box to the coils at (3), and then, with one end of the wire connected to the battery at (1), touch the other end to the (-) negative coil terminal (3). When you break this connection, you should see a spark at the plugs if your coils are good. If this does not produce a spark, check the coil wiring and (what else?) the connections, all the way from ground to point (3). If all connections are OK then you probably have a bad or open coil.
If tests 1 and 2 don't solve the problem, try the Boyer test #4 above. If you now have a spark, then you probably have something wrong in the triggering circuit, a broken wire or (what else?), that's right, a bad connection. Also, check to make sure that the magnet behind the pick-up plate is turning. Don't laugh, I saw' it happen once when the bolt holding it in the cam came loose.
In conclusion, let me say this about working with electronic circuits. If the circuit fails, it is usually fairly easy to find the trouble. The tests above will probably be sufficient to identify your problem. In practice, however, life is seldom so simple. Most of the time the problem comes and goes intermittently and can be very difficult to identify. One of the easiest ways around this is to substitute parts, one at a time, until the problem goes away.
The problem with the Norton on our ride was that it would produce only a very weak spark at the plugs. It required a voltmeter to determine that the box was turning on and off all right but the output was only about 6v instead of 12v. Replacing the box solved the problem. I think we all learned a little from this one.
Bayer has recently released an improved version of its electronic ignition. It uses a microprocessor based digital ignition unit. it is claimed that the triggering circuits are more stable, especially at low speeds, giving better idle characteristics. Starting should be improved, and the advance curve can be precisely programmed.
This article was taken from the "NORTON NOTICE". A newsletter of the Northern California N.O.C. Special thanks to the Editor, Alan Mueller.
BATTERY HAS POWER?: Switch on headlamp and activate stop lamp. They should
stay bright for more than one minute.
Return to Top of Page
Youve heard the term every time someone with a 2 wheeled Italian stallion rolls up. The S that sounds like a Z gives it an exotic ring. Heres an explanation from a chap from down-under (D.Grant).
Desmodromic valve operating mechanism is where the camshaft controls both the opening and closing of the valve. One benefit of this is that when the motor is over-revved, the valves are still controlled, whereas when the are returned by springs, then the valves can "float" and hit the piston. Another is that the manufacturer can use wilder cam grinds for better performance.
Ducati and Mercedes are two major companies who have used the desmodromic system in racing engines. Ducati has the most experience of any manufacturer in the world at successfully applying desmodromic valve control to production machines.
Note that in the diagram, the springs are only used to close the valve the last 0.005".
Valve clearances are adjusted by shims. The rocker arms have to be removed to insert the shims.
Return to Top of Page
Ever discover that there are some stripped threads on your aluminum transmission case? Here is how to repair the situation.
The Helicoil is the commonest type of thread replacement and is simply a spring-like coil of diamond profile wire (i.e. it's shaped like a diamond if you look along it) which terminates at one end in a straight bar that cuts across the diameter. A Helicoil drill bit which is slightly larger than the original hole is used to run down the hole to remove the remains of the original thread. A Helicoil thread tap is then run down the hole, cutting a new thread. The Helicoil itself is then wound down the new thread by means of a cylindrical drift with a slot in its end that holds that straight bit of the coil I mentioned earlier. The outer wedge of the diamond wire binds in the newly cut thread, while the inner wedge of the diamond provides the pitch of the new thread. Because it's made of springy metal stuff, it expands to fill the hole in a nice tight fit. Once in, you simply bash the end of the winding-drift with a light hammer, to break off the straight metal bar on the end of the coil, since its done its job and isn't needed. Because of this last operation, it isn't possible to reuse Helicoils. An old drill bit works good to break off the tang. Use one that fits snugly in the Helicoil and insert it point up and bang it with a hammer. That way you have a "drift" that fits correctly in the hole. Of course hitting the point isn't good for the bit, but it will be still good for drilling wood around the house.
The bad news about Helicoils is they sometimes wind themselves out of their own thread when you try to take bolts out of them, because they tend to grip the internal thread of the bolt.
In effect what the Helicoil does is remove the original thread and replace it with two new threads side by side, one of which it grips, and the other of which it provides itself, via its inner surface. For small (1/4 to 1/2 inch) threaded holes, they work very well. Above this size, and they start to give trouble, by not binding into their holes properly, breaking up inside the holes, or gripping the bolts instead of the inner threads. Sleeve type inserts are a better choice for repairing larger holes.
Helicoils are available for spark plug holes but there are strong opinions to avoid them here. It's very easy to drill out the old thread in the cylinder head at the wrong angle. When that happens the spark plug will not seat properly. A good alternative is for spark plug holes is the Timesert, which is a special type of sleeve insert. This comes with its own stepped tap to cut the new thread. This tap is ingenious because the lower portion of the tap is threaded, so that it can be led into the remnants of the damaged original thread, thus ensuring that the alignment is correct before the second half of the thread follows on behind and cuts the new thread. Care is needed, if the original thread is in a bad way, but it's much easier than the drilling and re-tapping from scratch option that is needed for Helicoils.
By the way, Timeserts are available in the US, along with other brands and variations Keenserts and Recoil.
Edited from the Internet
Return to Top of Page
The spark plugs of today are not what they used to be. The famous Lodge H1 spark plug really had character. You never knew whether they would fire or not. If they didn't, it was just a matter of whipping out a spanner, disassembling it (yes, they came apart!), cleaning it, and re-assembling it. That usually got you on your way again.
Time, patience & some oil go a long way.
Remove the heads & every day pour some very thin oil on the tops of the pistons. The idea is to have the oil form a puddle and leak past the rings. Hopefully this will require periodic topping up. A good indication of leakage. At every top off visit, whack the tops of the pistons with a wooden mallet before replenishing the puddles to try to get some movement. As soon as there is the slightest perceptible movement you know you have won. The next step is to rock the crank back and forth as much as it wants to turn. Keep this up until the barrel can be removed.
If you dont have the patience for all this, get tough. This means heating the barrel with a torch to get things bigger. Find a nice piece of oak like from an old hammer and have an assistant, preferably someone with strength, hold the engine off the ground by the barrel. This gives the bottom part of the engine a place to go on impact. Use a 3 pond mini-sledge hammer & hit the pistons sharply through he wood drift. After awhile youll be able to determine if the combination of heat & hammer will free the pistons. If not then the next step is to drill out the pistons. Use about a 1/4 inch bit & drill around the sides of the barrel. Be careful not to damage the cylinder walls. Apply some more heat & hammer. The pistons should come free. Try to disintegrate the piston as much as possible because the cylinder skirt has a habit of cracking when the piston is hammered though.
AND Another Method.
I too have used the above method on a stuck MGA motor once but I have found
a much safer and easier way. I worked as a mechanic in a Triumph/Norton
dealership in OKC during the 1980s. Every spring we would see a rash of bikes
with stuck pistons. We found this was mainly due to long term storage in a
garage with an unvented drier. The cylinder with the open valve would rust up
and cause the piston to seize.