With the decreasing availability of OEM Honda (and other makes/models) ignition coils, the only alternative appears to be the Chinese-made copies of single—and dual-output ignition coils that flood the eBay market listings.
I recently had an exchange with one eBay seller about this listing:
High Voltage 12V Ignition Coil For Honda CS90 CL125S CL100S S90 SL90 XL100
I pointed out that none of these models use a 12v coil, but the replies were vague and unhelpful.
This listing:
6 Volt 1 Ohm Ignition Coil Dual Spark Plug Output for Honda And Others 24-72454 shows the application chart including CB92, CA95, CA160, and CM400T! I doubt that it will last more than a few minutes, as a 1-ohm coil is designed for electronic ignitions.
Case in point:
Recently, my friend Steve P. was finishing up his wonderful restoration of a 1961 Honda CB92 and Hs purchased an aftermarket coil from an eBay seller. After re-checking the cam timing, ignition timing, carburetor jets and metering circuits, he was unable to get the bike to fire up at all. I made the usual suggestions about the basics, which he checked out thoroughly, but still no joy when he hit the starter button, even with some starter fluid sprayed into the intake.
I agreed to come by his place and check his work and the bike over, looking for any concrete reasons why his restored engine and bike were stubbornly inert. The compression tested out to about 100 psi, equally on both sides. We verified that the cam timing and valve lash settings were all correct. The point gap was .014” and they were opening at the F mark.
With the spark plugs still out after the compression test, we grounded the plugs for a spark check. Initially, there seemed to be a strong spark, but in repeated cranking the spark became erratic and finally pretty much quit altogether. One thing that can upset spark creation is a failed or disconnected condense. But when it has a problem, the points will arc heavily during cranking or engine operation attempts. This was not occurring in this instance.
Having checked and eliminated the main possible culprits and noting the diminishing spark output, I pulled the coil primary leads off for an ohms test. The ohms test for the supposed 6v dual-output coil read out at 4.5 ohms. That is a reading expected of most vintage Honda coils that are of the 12v variety, but not for 6v types. When we checked his removed OEM coil, it tested out at about 1.5-1.8 ohms, which is what you would expect from a 6v ignition coil.
So, what was happening is that the 12v coil, being fed a diminishing 6-volt supply, was dropping lower with each electric starter test cycle until the voltage dropped below the cut-off limit. The higher resistance of the aftermarket coil curtailed the spark output on a steady decline until it ceased.
It’s easy to see an initial spark at the spark plug on a quick check and assume that it should be enough to run the engine. In observing the decline in spark activity through prolonged engine cranking, you get a truer picture of what is happening. This is a vital clue to troubleshooting an ignition system issue.
In an earlier blog story, back a few years, I wrote about buying a CR93 street bike tribute bike, based on a CB160 chassis with a 5-speed CL175 engine installed. Ironically, I had owned the bike and sold it at a swap meet event in N. Cal. The tank and seat were actual CR93 components fitted to the CB160 chassis. I could see that a great deal of detail work and restoration work had been done to the bike, during its surprise, last minute entry at the Las Vegas Auction. I felt compelled to buy it back and did actually win the auction in the end. https://www.mrhonda.guru/2017/03/the-beast-within-beauty-cr93-replica.html for the story.
The bike had not run recently, so I went through a basic check to see how the basics were doing before trying to start it up. The carbs were cleaned and one float was found to be sinking. Once the carburetion was dialed-in and ignition timing checked, the bike fired up quickly on a fresh battery, but it wouldn’t run more than a few blocks before it began to misfire and finally quit altogether. Backtracking over my previous work and rechecking all the obvious causes, I finally realized that the spark to the plugs was becoming erratic, after just a few minutes of operation.
The CB160/175 series of bikes are all equipped with 12v charging and ignition systems. Finally, I noted that the ignition coil was an aftermarket copy and checked the primary resistance. It was about 1.8 ohms, which is something that you would see for a 6v ignition system or in some cases bikes equipped with electronic ignition systems. Most full electronic ignition systems use coils in the .3 to 1.5 ohm range. When these coils are substituted on a 12v system using points and condenser, the high current draw will burn out the primary coil windings pretty quickly.
Sure enough, when I replaced the coil with one of the 4 ohms range, the bike started immediately and continued to run for an extended period of time without any mis-firings or performance issues. Recently, a customer bike came in with perfomance problems and on a single-cylinder vintage Honda machine and when the coil was checked, it too, had a 4-ohm coil instead of something in that 1.5-1.8 ohm range.
In looking at some of the various eBay listings for aftermarket coils, few, if any, have ohm specifications listed. Because motorcycle coils come in just a few sizes and mounting dimensions, it seems that the sellers are pushing out products that are inappropriate for the desired applications. Typically, you will see the same photos of the same coils listed by various named eBay vendors who are either all working together or all getting the same products from a few manufacturers in China.
Asking questions about the specifications is often a fruitless endeavor, as they are not tech-savvy vendors. They seem to take your questions and then refer to the suppliers in China. I imagine that there are translation difficulities all around, which make finding out the details of a component difficult or impossible.
So, all I can say is BEWARE of aftermarket products, especially in the category of ignition coils. DO NOT buy from one who is unable to supply the correct ohms specifications for their products. Their cheap pricing is enticing, however you may well find yourself scratching your head for hours wondering why the bike won’t run even though you have changed the whole ignition system.
This one small detail makes all the difference in success or frustration when trouble-shooting the cause of engine performance failures. Once Steve replaces his coil with one of the correct primary winding impedance (or puts the original one back in place), the bike should fire up properly and he’ll be a happy man. I feel that this is an important issue that needs to be remembered in times of frustration and confusion after a bike build or repair.
Bill Silver
aka MrHonda
Nailed it again Bill, good info!!
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