Tech Forums > SOHC/4 Bikes

no spark

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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 IGN - bike should run, key cannot be withdrawn.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 PARK - park lights work, key can be withdrawn.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

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