Topic: no spark

[mongeon]

I just bought a 74 cb550-four.  I have never worked on engines before, so please forgive me if I ask stupid questions.

I can't get the bike started.  I can't get the spark plugs to spark when I take them out.  The lights all work.  When I turn the key to the middle setting on the ignition, the oil light and the neutral light come on (when it is in neutral).  Sometimes I have to jiggle the key to get this to happen.  When I turn the key all the way, nothing works.  I don't know which position I am supposed to have the key when I start the bike.  I have tried it in both positions.  I had the engine cutoff set to run, and I had the fuel switch on.  I can't think of any more info.  Please help.

Chris

[Bob Wessner]

You didn't mention it, and I don't mean to be condescending, when you say you can't get the spark plugs to spark when you have them out, are you grounding the plug to the engine when you do this? The outer electrode has to be grounded. Don't do it with bare hands though, use a dry rag.

[mongeon]

I did touch the spark plug to the engine and hit the starter.  Somebody mentioned that I can just take the cover off and put a screwdriver in it, and touch the screwdriver to the engine, which I have also tried. 

[Patrick]

I'm something short of an expert, but here's a couple things I might try. First, try to find out if there is fire going to the plugs. Find the distributor on the right side of the engine (as you sit on the bike). Trace the wires back til you find a connection. On my CB750 this connection is in front of the oil tank. I've never worked on a 550, so I don't even know if you have an oil tank, but I know the wires from the coils to the distributor have a connection somewhere along the way. Disconnect the wires, turn on the ignition and use a test light to make sure both wires are live. If they are, reconnect and go back to the distributor. Pull off the distributor cap. Touch the test light to the wire connection on each set of points and, with the ignition on, turn the engine over. The test light should flash as the points open and close. If it doesn't light, your points may be bad or dirty. Try cleaning them with some contact cleaner and try again. If you have spark at the points (this is all assuming you have points and not an aftermarket electronic ignition, with which I can be NO help)), then reconnect everything and pull a spark plug. Make sure it is clean and properly gapped. I usually get best results by touching the plug base to a spot on the frame where the paint has been chipped off. Of course, MY bike doesn't have any paint chipped off, since it is perfect in every respect (it's listening). If you have stainless steel crash bars, they work even better. Ground the threads to steel and try again. You have to make sure you have a good ground for the plug to fire. If after checking and cleaning all the connections between the coils and the plug you find you have fire at the points but none at any of the plugs, then I have no more ideas and I would type in a request for help to the SOHC-4 site - which, of course, you have done. Did I mention that I am something less than an expert?

[rpyles]

I'll try a shot at it. On the 750 the ignition runs through the headlight bucket. If anyone's been in there, you could have a loose connection. The bike will crank, but no spark. This is the same as cranking with the kill switch in 'OFF'. Your ignition key should be in the middle position. The top position just turns on the taillight, and lets you remove the key, in case you have to park along a roadside.
Good luck.
Richard

[SteveD CB500F]

You didn't say whether the bike was running before you bought it, and if so, how long ago.

If it's been sitting, I would buy a new set of plug for starters and probably a new set of plug caps.  Buy a manual.

Then do a standard tune-up service including oil, filter, air filter, timing, BRAKES (!), chain, tyres.  Buy a manual.

Now, does it start?  If not, go back to basics: Fuel (are plugs wet?), Air (carbs leaking?), Spark.  Buy a manual.

The key should have three positions:
1. OFF
2. IGN - bike should run, key cannot be withdrawn.
3. PARK - park lights work, key can be withdrawn.
At least, that's how it works here (UK) - other markets may be different.

If you have to jiggle the key, this is bad news and probably means that the ignition switch is broken (on my 500, one of the wires came unsoldered/broke off) - this is very dangerous as the lot may go off just as you pull into the overtaking lane at 90+  ...

Oh and did I mention, buy a manual. The best investment you can make.

While you are doing all this, keep in touch via this board.

Good luck

[mwvachon]

My 2 cents:
- You may also want to check the kill switch and it's connections. If there is a short, this will cause the no-spark condition. I don't even want to suggest that you check to insure the kill switch is NOT in the OFF position (this switch is just above the starter button). I remember when my Dad bought a CB350 back in 1970. It wouldn't start and he pushed it about a mile or so before realizing he neglected to check that - UGH!
- As to the ignition switch, yes std. key positions in the US are the same as SteveD noted. Should be in the #2 position to start. If jiggling the key is causing the circuits to intermittently fail, the key switch is failing. It is possible to disassemble the ignition switch. The harness goes into a metal cap that is crimped onto the tumbler body. You can use a small flat screwdriver to pry the crimps open and remove the metal cap, Inside you will find a drum with 3 contacts on it that make connections as the key is turned. Clean up all surfaces and check for wear damage. I did this on my '71 K1 and the drum had a defect in its face that was causing poor contact. You may want to put a bit of conductive lubricant in (not too much!) before reassembling. You can usually clamp the assembly back together and recrimp with a small punch. I gingerly placed mine in a bench vise with a cloth wrapping on it and LIGHTLY closed up the vise and did the recrimp. NOTE: This is only a temporary fix - your best bet will be to replace the ignition switch at some point, lest you get stranded at some future point!
Good Luck!

[mongeon]

Thanks for all the replies.  I do have a manual.

I seem to be getting power to the ignition coils, and I was told that one of the coils might be bad when I bought the bike.  I guess it is possible that both coils are bad.  I guess I will buy one coil and see if that helps half the plugs, rather than buy two and find I was wrong.

Any more suggestions are welcome.  I will let you know how it goes.

Thanks again.

[Bob Wessner]

One of the posts earlier suggested you check the condidtion of the points, wondering if you did? I ask because when I first took my 750 out of a long storage, NONE of the electrics worked save for the neutral light and one non-blinking turn signal. At the suggestion of all here, I went through the harness and cleaned every connection. Everything worked after that, but could not get a spark to any plugs. All I had to do was clean the points with some very fine grit emory cloth folded over and dragged though the points when closed. Got sparks to all four plugs immediately. Just a thougth. Also, seems odd that both coils would fail at precisely the same point in time. I would explore other options, replacing them, and the cost ought to be a last resort.

[CHUNG]

The black wire to the right-hand switch is hot and it comes back from the switchgear as black/white stripe. This is the power to the coils. The power FROM the primary on the coils will be a yellow and a blue wire to the points, (one each, forget which side is blue?) that is the ground for the primary windings on the IGN Coils and you will find a set of plugs near the rear brake on that bike. Not tooo complicated if you undersdtand the basics. I can help with the basic troubleshooting if needed, Have your people contact my people via email. LOL CHUNG

[mongeon]

The plugs are now sparking.  I think it was the contact breakers.  Thanks for the advice, and saving me from buying new coils unnecessarily.

Oh, and it seems to have fixed the ignition problem too.  It doesn't need to be jiggled anymore.