The Service Dept
THE SERVICE DEPT
JODY NICHOLAS
WHY CDI...WHY NOT!
In the Kawasaki test in the January issue, you state that the cost of C.D. ignition is prohibitive. If that’s the case, why does Chrysler have CDI as standard on all its domestic cars down to its cheapest model? Why can they afford it on many medium-priced outboard motors and snowmobiles? Even Lawn lawnmowers have electronic ignition.
The test of the Mach II (sic) in the Sept. ’71 issue says that CDI costs almost $100. Where do you get those kinds of figures? It seems you must be checking the price of replacement parts at the parts counter (in which there isa tremendous profit at the dealer, distributor and factory level), and assume that if the factory equipped all their Mach Ils (sic) with CD ignition they would have to raise the price nearly $100 to make the same profit.
You can buy accessory units for less than that which have everything except the magnetic pulse generator. And you know how much profit they make. With contact points costing $10.32 a set, if you replace them every 75 00 miles that’s over $40 saved in 30,000 miles
«Iñth I ark a plugs. CDI, Then let alone you scare the your savings readin ers out of CD ignition by mentioning the poorly designed black boxes on the early H-ls.
In that case they should work out the bugs, like they’ve done on the 500s, rather than go back to Stone Age ignition systems. Conventional ignition isn’t all that reliable with the fouled plugs and seized pistons caused by overly retarded timing due to point wear.
The point I’m trying to make is that ill-founded logic like this miseducates the readers into demanding crude, outdated bikes, while car owners, outboard owners and snowmobilers are enjoying truly reliable, maintenance-free ignition systems. Charles Hagg Eau Claire, Wis.
The points you tried to bring out in our letter are well taken, and I’m sure they were well intended. However, there are several places where you are obviously confused, and, in at least one instance, we might have led to part of this confusion. I’ll take your comments and questions and try to clarify them, for your benefit, as well as for the benefit of our other interested readers.
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First of all, the Mach II test you refer to was, in fact, a test of the 350cc S2. The new 400cc S3 is called the Mach II.
Secondly, our remark, “It seems strange that Kawasaki has stuck to the battery and coil ignition system with its three sets of points, until one considers the prohibitive price of the CDI unit,” was not the best one we could have made, especially without further explanation.
There are many things a factory has to think about when designing a moteja cycle offered for sale to the genei^P public. Each time an unusual item is added to the machine, the cost of the machine goes up, for the distributor, dealer and customer alike. And each time the price of a machine goes up, it looks bad to the customer who is comparison shopping for different machines in the same engine displacement category. So the factory has to decide: is a CDI more attractive to the general buying public than, for example, a disc front brake? To add CDI to the S3 would raise the retail price approximately $75.
Where we get “those kinds of figures” regarding the cost of a Kawasaki CDI is from a Kawasaki dealer; the prices a customer would have to pay to replace defective CDI components, or to convert his battery and coil-equipped bike to a CDI system.
As an example, the CDI on an ear^^ model Kawasaki HI 500cc Three has some very expensive components. Not counting the AC generator per se, the system has a pickup coil ($7.20), a signal generator rotor ($16.40), a Unit A black box ($59,00), a Unit B black box ($64.00), one ignition coil ($8.70), and a distributor ($15.90, not including the small fittings). Neither the prices for replacement parts, nor the actual cost of a Kawasaki motorcycle are fair-traded.
The “bad design” of the early black boxes was not that at all: the black boxes have their internal components encapsulated in an epoxy material to aid in preventing failure from high-frequency vibration, and they are mounted in shock-resisting rubber. It seems that the Japanese design wasn’t bad at all, but the execution left something to be desired.
By contrast, the conventional and battery system used on the new Mach II 400cc Three uses, again not counting the cost of the AC generator per se, three sets of contact points ($3.20 ea.), and three ignition coils ($8.70 ea.). It is a much simpler system which has worked satisfactorily for a number of years.
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The “accessory units” you refer to might or might not be compatible with the rest of the system, but no, I don’t know how much profit they make.
And no, the Chrysler Corporation “CDI as standard on all its domestic cars down to its cheapest model,” is not a CDI. Rather, it’s an electronic ignition system that differs from a conventional coil and battery system only in that it uses an electronic device to trigger the spark, rather than a mechanical one like a set of points. Tawn Boy lawnmowers fall into the same category in that they have a magnetic device which serves as a contact breaker: an electronic ignition, to be sure. Just as a point of interest, a friend of mine replaced the coil on his similarly equipped lawnmower last summer, and it cost him slightly over $17!
Oversimplifying the explanation, I will give you some of the advantages and disadvantages of all three types of ignition systems.
With a conventional system a slightly longer time is required to produce the required voltage at the spark plug. The contact points can get dirty and out of adjustment, and there is a remote possibility of “point bounce” at high engine rpm that can cause misfiring. However, in almost all instances, a properly designed conventional ignition system will provide more than adequate voltage to fire the spark plug(s), even under marginal fouled-plug situations. These circumstances are usually provoked by a poorly serviced or improperly ridden machine. For example, a bike with an over-rich oil injection and/or carburetion system, which is ridden slowly (at low engine rpm), will more than likely foul the spark plug(s), CDI or not!
A transistor system using conventional contact points provides a faster voltage rise time, which aids in firing partially fouled spark plugs, mostly because of the superior ignition coil design. However, the current at the contact points must still be in the neighborhood of 1.0 amp to insure that a minimum of misfiring occurs when the contact points do get dirty. A transistorized ignition system with a magnetic or electrical triggering device does not suffer this problem.
Even though a transistorized ignition system will help fire partially fouled spark plugs, spark plug life is most often not longer than that provided by a conventional coil and battery ignition system. The higher voltage which helps to fire the spark plugs also makes them wear out more quickly, due to faster erosion of the electrodes.
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Several advantages do accrue to the use of a CDI system such as the one used on the Kawasaki. One is that there are no contact points to wear or get dirty. The spark has a faster rise time, and a higher voltage is available at the spark plug. Cold weather starting is improved slightly, but claims made about better fuel economy are generally overstated: a 5 percent increase would be likely, but there would be little, if any, power increase over a correctly functioning coil and battery system.
A disadvantage of the CDI, in ad^b tion to the high cost of replaceml^P parts, is that the high voltage current will “leak past” bad wires and connections much more easily than with a conventional system, causing shorts, blown components, etc.
Most of the racing motorcycles supplied today use a “magneto CDI” system. For example, the TD and TR-3 Yamahas, the Triumph and BSA 750cc four-strokes, the Suzuki TR-750 and the Kawasaki H2-R road racing motorcycles all use a variation of the “magneto CDI” ignition system, in which a generator, rather than a battery, is depended upon to supply the required current. A notable exception is the Harley-Davidson XR, which uses a magneto ignition.
Just as a point of interest, I researched your question(s) a bit further and got in contact with Bob Liebeck, who is a design consultant to Ij^b Gurney and his successful racing ai^^ mobiles at All American Racing, and with John Miller, a Dan Gurney employee who is very knowledgeable about the engines used for championship car racing in the United States. For your information, the Offenhauser dohc four-cylinder racing engines use a “magneto CDI” system that works very well for them. These engines turn in the neighborhood of 8200 to 9500 rpm, depending on the size of the race track they are built for. This system provides a spark of very short duration: in the neighborhood of one degree of crankshaft rotation. Most of the dohc Ford engines that are still being campaigned in championship car racing, use an ignition system whose firing is controlled by conventional contact points. This helps give a longer spark timing: in the neighborhood of 10 degrees 4fe crankshaft rotation, which helps these engines perform better.
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Another interesting sidelight: none of the Kawasakis sold in Japan or in Europe are fitted with CDI. The reason? CDI is responsible for a large amount of RF (radio frequency) interference in the 200-500 kHz waveband, which is the one most commonly used for radio broadcasting in those parts of the world.
Once a set of contact points has established a “rubbing surface” on the fiber block, which rubs against the point cam lobe to open the points, very little more wear will occur if the point cam is supplied with lubricant as recommended by the manufacturers. That is one reason why Kawasaki, for example, specifies a service check be made by an authorized Kawasaki dealer at 500-1000 miles, within one month of the date of purchase. Most of the initial wear take place during the first 250 ormiles of use, and the dealer is expected to check the point gap as well as the ignition timing at these services.
The problem of retarded spark timing on the Kawasaki S3 due to contact point closure that is caused by a worn point fiber block can get serious if it is allowed to get too far from the recommended setting.
Contact points are normally set between .012 and .016 in., with .014 in. being considered ideal. Assuming that a point setting of .014 in. gives the ideal timing figure of 2.6 mm btdc (or 23 deg. btdc), an increase in the point gap to .016 in. will cause the timing to advance to 3.9 mm btdc (26 deg. btdc).
Conversely, reducing the point gap to .012 in. will retard the spark timing to 2.3 mm btdc (21.5 deg. btdc). But the buildup of metal transferring from side of the contact point to the otl^^ caused by “arcing” or dirty contact surfaces, will tend to advance the timing back towards the position from whence it came.
The point I’m trying to make here is that there is no substitute for regular, conscientious maintenance of every motorcycle. It is usually true that CDI systems without contact points will require very little maintenance. But when the bike with a CDI does stop running, chances are that it won’t run again until a defective component is replaced, whereas a conventional coil and battery system can often be made to operate by cleaning the contact points!
So you see, CDI is not a panacea, even though it works very well in most situations. It will be a long time before you can rightfully call properly designi^^ and executed coil and battery and ma^ neto systems “Stone Age ignition systems.”
