No spark on my 75 CB550F

2266 Views 18 Replies 5 Participants Last post by joe c, Oct 4, 2006

kine8282`

Discussion Starter · Oct 1, 2006

Howdy...hope someone can help me out.

I don't have spark on my CB550F. I bit of history on the bike; I just got it last weekend from this guy who said that he was changing the handle bars and once he finished he couldn't get it started. A buddy on mine just came over this morning to look at it...checked the usual suspects; points (good), battery (new), plugs (good condition). Electronics was his kryptonite so he couldn't figure out why I wasn't getting any spark.

I lights and horn work so I don't think its the battery. I just checked the birds nest of wires behind the headlight and everything seems to be in order, I did find a brown female connector without a partner but according to my Clymer brown is for the taillight and that works just fine.

I was trying to find a thread for this on the forum but nothing was working...can anyone offer help? Thanks.

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kenessex

· #2 · Oct 1, 2006

Since you ar not getting any spark on any cylinders then the problem has to be either power to the coils or kill switch. Check the wires from the ign. switch and the wires from the right handlebar switch. Off hand I don't recall tthe color codes for sure but I think the switched hot from the ign switch to the coils is solid black and the kill switch is black with a white tracer(possibly yellow). If the insulation for the kill switch wire got cut or pinched during the installation of the handlebars it will be shorting out and killing the spark. If you unlug the kill switch wires and the bike has spark then your culprit is somewhere in that circuit. If that doesn't fix it then check to see if you are getting 12V to the coils at the black wire, not the yellow or blue(they come from the points).

Good Luck,
Ken

AHRMA 412
Vintage racing - old guys on old bikes

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kenessex

· #8 · Oct 2, 2006

Ok, I just looked at a wiring diagram and the hot lead to the coils is a b;ack ith white tracer. It comes straight from th ill switch. At the coils see if the blackw/white has power if the ign switch is on. If it does then the you should have spark. If it doesn't then pull out the headlight and sart checking the wires in there. This is a simple process if you follow the steps. You don't need to tear switches and stuff apart yet.
1. Unplug the connetor for the ign. switch. White rectangular plug. Is the Red wire on the main wiring harness hot(12v)? No? Check your main fuse or battery connection.
2. Check the ign switch for continuity between the red and black. With the switch off no continuitty, switch on there should be continuity.
3. check the connectors from the right handlebar switch. (individual connectors) Check the black to the switch, is it hot with the ign. on? Check the Black w/ white tracer, with the black wire connected is the black w/ white hot with the ign switch on? If not, connect the black straight to the black with white tracer bypassing the kill switch. Spark now?

Somewhere in these steps you should find the problem. It isn't rocket science, just take your time and be logical.

Ken

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Vintage racing - old guys on old bikes

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kenessex

· #10 · Oct 2, 2006

Just in general, when dealing with an electrical problem always look for common factors. In the case of Honda ignition systems on 4 cylinders, they run paired ignition systems. That means that if the spark is missing in cyl. 1&4 or 2&3 together then the problem is in the coil or points or the feed or ground to that coil. If the spark is missing in only 1 cylinder then the problem is the wire, cap or plug. If the spark is missing in all 4 cylinders then the problem must be in the power to both coils which comes through the ign switch through the kill switch to the coils. Again, with the twins with 2 coils, try and isolate it to one side or the other or if spark is missing from both cylinders look for the common factor. If possible, get a wiring diagram and start tracing wires. The other nice thing about Honda is that their color codes are consistant throughout their models, so any Honda wiring diagram will give you a good idea of what to look at.

Ken

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kenessex

· #14 · Oct 3, 2006

Joe,
The problem is that the breakeven point on those models was about 2200 RPM with the keadlight on. The cure is to keep the RPMs up and put a switch in the headlight circuit so you can shut it off while the bike is sitting warming up. Ride it like it is somebody elses and you won't have a charging issue.

Ken

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Vintage racing - old guys on old bikes

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kenessex

· #16 · Oct 3, 2006

Joe,
Yup it is stupid to have to put a headlight on off switch on it, but that is the way it is. Honda did the simple thing in 75 when the law said that headlights had to be on all the time. They just took off the switch and left everything else the same. On some bikes the system was good enough and matched the riding style of the owner and Honda got away with it. On other bikes of the same model it wasn't good enough and the batteries went dead. My sister and I both had 1975 CB400Fs. Hers needed a headlight switch and mine didn't. When I used hers I didn't need the switch, cause I rode it like it was hers. I did crash it twice and tore out the oil drain plug on some railroad tracks. It sucked taking good parts off mine to replace her stuff so she didn't know I beat it.
If you want to throw parts at it that may or may not do any good, sometimes the regulator rectifier on those could be replaced and make a difference. Other than that rev it out and throw it on the trickle charger every couple of days.
P.S. It has a kickstarter.

Ken

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