Topic: 1981 CB900 ignition coils on a 1976 CB550

[Phaedrus]

This may work for other years for both coils and CB550s but I would have no clue. 

Get your coils with the bracket attached to them.  The coils I got were from a 1981 CB900.  After inspection of my bike I determined that I had to take the rear bracket off the coils and turn it upside down.  The tab that mounts to the frame is offset to one side so make sure when you flip it, it is on the same plane as the front bracket in relation to the frame. 

Now the control wires on the CB900 coils are in the back of the coils versus the CB550 coils where the control wiring comes in on the front.  That is about the only difference (save the replaceable plug wires).  So I had to move the green ground wire to the rear bracket bolt to get the bike harness leads to the back of the coils.  The coil with blue lead goes on (the riders) right, just like the old coil, coil with the yellow lead on the (riders) left.  The color codes match up, just like the old coils.  Right Coil, cylinders 1 and 4, left coil cylinders 2 and 3.  You will just have to cut off the factory wire harness from the CB900 coils and attach bullet connectors to the leads.

The power leads to the 550 coils were two wires, one for each coil.  The 900 coils have only one hot lead to get power to the coils, so you will have an empty hot lead in the harness on the bike, if yours is stock, it is surrounded by lots of plastic, so not much of a chance of shorting out.

Now you have coils with replaceable wires, and a better spark.

[cb650]

Isnt the 900 a electronic ignition?



            Terry

[Phaedrus]

Isnt the 900 a electronic ignition?



            Terry

Oh yeh, I am running this with a Dyna S ignition system too.  But a switch is a switch (in my mind at least) I dunno why this would not work with points.

[puppytrax]

...I dunno why this would not work with points.

Me neither. I just scored a set of 81 HONDA CB900  COILS on eBay...Eventually I'll get around to swapping them in...

Any other little pieces of info for this swap??? How about them bullet connectors??? Are they a stock item somewhere???

[oldfart]

Yes, it's an electronic ignition, but it still fires on collapse, so the coils are really no different.  However, they are not any better, either.  :-)

[puppytrax]

Yes, it's an electronic ignition, but it still fires on collapse, so the coils are really no different.  However, they are not any better, either.  :-)

Replaceable wires are better for me...besides...would a Gonzo Motorcycliste lie???  ;-)

[oldfart]

Yes, it's an electronic ignition, but it still fires on collapse, so the coils are really no different.  However, they are not any better, either.  :-)

Replaceable wires are better for me...besides...would a Gonzo Motorcycliste lie???  ;-)

I agree with you in theory.  But why would you ever need to replace the coil wires in a SOHC Honda?  Below is an article addressing the whole coil wire, plug cap thing.  Take a look.  :-)

http://www.motorcycleproject.com/motorcycle/text/plugwiretech.html

[puppytrax]

But why would you ever need to replace the coil wires in a SOHC Honda?

Let's rephrase that question and put it in context...Why would you want to replace 33 year old, cracked, oil soaked, baked, and brittle coil wires in any engine???

[oldfart]

Well, cracked insulation I can understand, but 33 yr old makes no sense.  Did you read the article?  Those coil wires are permanent, they do not "age" like auto wires do.   

[DrMark]

I did the same swap on my 1978 CB550 last summer. It was fairly simple and straightforward. I flipped the mounting bracket and matched the wires. Initially, I kept the points and condenser....ran great. Later, I changed to a Dyna-S ignition system...runs better. I found my set on EBAY for $14.95. I went to Honda Shop and bought bulk spark plug wire for $1 per 2 feet and purchased new NGK caps. Total cost: less than $30.

[puppytrax]

Well, cracked insulation I can understand, but 33 yr old makes no sense.  Did you read the article?  Those coil wires are permanent, they do not "age" like auto wires do.   

Only in a perfect world. Have you ever replaced the duplex receptacle in a 1950's vintage house??? You probably found that the wiring (usually copper) was crystalized, and the wire crumbled when you tried to coil/uncoil it from the receptacle. Metal will "age" even if not subjected to handling, which can work-harden the metal and cause it to fatigue early. Aluminum (which "modern" houses have) is even worse. Japanese spark plug wires are not immune. Insulation will dry out and crack as well.

Back to the coils...My two bikes have not been pampered, or kept in a warm air-conditioned environment. The coils are probably still good...but the wires have dried out into a stiff and likely fragile state...They have to be handled and bent just to get to the plugs...even if the wire doesn't break or corrode, the covering will crack and probably cause problems in a humid or wet atmosphere...

That's the theory behind swapping out old coils...

...But I just like to try out neat ideas... 

(I've already got the hat...I just need a cigarette holder...)

[oldfart]

Ah, you will have to humor me.  I am still stuck in the 1970s...  Thanks!   

[puppytrax]

Ah, you will have to humor me.  I am still stuck in the 1970s...  Thanks!   

I'm still stuck in the '60's!...My first bike: Yamaha YDS-3 [250 2-stroke twin] bought used in '68...It topped out at 87mph...indicated...but it would keep up with the 305 Hondas... 

[puppytrax]

Later, I changed to a Dyna-S ignition system...runs better.

What's the story on these Dyna-S ignitions??? Are they still made???

[puppytrax]

The coils I got were from a 1981 CB900...You will just have to cut off the factory wire harness from the CB900 coils and attach bullet connectors to the leads...Now you have coils with replaceable wires...

Phaedrus - you didn't mention if you replaced the CB900 plug wires or used the ones that came with the coils...I'd be interested to know if the CB900 wires will reach the CB550 plugs or if new wires *need* to be cut to size...

(BTW: what ohm reading did you get on your CB900 coils???)