cdi on the cb650? www.motorcycleproject.com

®	CDI on the SOHC four CB650?

This, just one of literally hundreds of notable instances of unqualified, extemporaneous drivel on powersports forums such as sohc4.com, exemplifies very well the entrenching effect of inexpert opinion presented as fact on forums. Sohc4.com's confident and repeated declaration that Honda put capacitor discharge ignition (CDI) on the SOHC four CB650 is patently false and demonstrates a vacuum of knowledge about the machines the forum pretends to be expert on. Every professional knows this bike does not have CDI. Even just a little time spent with the bike would inform a person of it. You don't even need the official manual. All you need to do is remove the right side crankcase cover. There you will find Honda's classic "pulse generators", the ignition triggers used on all of the company's 80s Transistorized Pointless Ignition (TPI, Honda's official nomenclature for transistorized Kettering) bikes. If you need further validation, simply remove the seat. Now you'll see the two ignition "spark units", those boxes containing the TPI's transistors. These two parts, the pulsers and the transistors, are exactly the same as found on virtually all of the strictly road-going Hondas of the late 1970s and into the mid 1980s, and even well beyond, from the late CX500 up through the the CBX1000 and the venerable CB1100F, plus all the V4s, and all the CBRs. Easily 90 percent of Honda's total powersports production has TPI ignition. While a few dual purpose vintage Honda models can be pointed out that have CDI, and of course there is the very unique cases of the 400 parallel twins and first few years of the CX500, CDI has made very rare appearances on production Hondas even to the present day. CDI is in fact very rare in all of Big Four's streetbikes. There may be many reasons, but one very good one is because it is not very compatible with streetbike fueling.

"Thin feeling"? Whatever that means. Completely extemporaneous. And all this about adding resistance to improve performance? Whatever. If the visual checks above aren't enough, if the obvious visual clues don't convince, then do a spark test. You'll find that the plugs fire on ignition coil collapse, very unlike CDI and a very classic and nearly defining attribute of Kettering.

Still not convinced? Then open the official service manual and look at all the diagrams and text that refer to a transistorized Kettering system. Absent are any symbols, images or verbiage that communicate CDI. Anyone familiar with Honda wiring schematics will immediately conclude the 650 does not have CDI.

It is unknown why sohc4.com insists on this foolishness. While it is true that many online parts sources refer to the CB650's ignition as CDI, they do so with the DOHC CB750 and CBX1000 as well. Of course, many aftermarket repair manuals make the same mistake. (Perhaps it is most forums' peculiar advocacy of these error-prone publications that fosters their own aberration.) This habit of calling anything without points "CDI" is a humorous and quaint artifact of the general public's traditional misunderstanding of powersports ignitions, and consequently is almost to be expected of the uninformed. In fact, it is very common for transistorized Kettering to be confused with CDI, and even more common for magneto and energy transfer to be mixed up. However, to find it perpetuated on a forum that both expressly and by implication exists to technically educate its readership is, to say the least, disappointing and unfortunate.

I have of course pointed this out as a fallacy to sohc4.com leadership, specifically the individual making this claim. Instead of dialoguing with me about it, the individual doubled down in his rhetoric on the website.

Sohc4 continues to insist not only that Honda's Kettering system is CDI, but similarly that it fires on buildup and not on collapse. The poster also seems unaware of the history of CDI as developed for motor vehicles. This not only demonstrates this poster's lack of understanding about Hondas, it also belies his self-stated knowledge of electronics.


This is CDI.	This is not CDI.