cb 750 unusual misfire

[Nigellynch]

I have a restored cb 750 four k5 US import. I've installed electronic ignition and modern rectifier/regulator.
Everything is fine, except for an odd misfire. This happens only when I switch the indicator on, and is only a little hiccup while the indicator switch is between off , and on.
Any ideas?

[SteveD CB500K0]

Does it happen EVERY time you switch the indicators on?


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[Rob62]

I noticed when rebuilding my K4, that the contacts in the handlebar switches do come very close to the handlebars, so much that i decided to put a bit of insulating tape on the bars just to eliminate any contact.... I wonder if there is something contacting and shorting on yours? Maybe worth loosening and removing the switch gear from the bars (both sides) and then trying the indicator switch to see if you still have the missfire..... worth a try, only a 2 minute test to eliminate it.

[Nigellynch]

not every time, when I think about it,

[Nigellynch]

that's a good idea Rob62 , Ill try your advise but I still don't know how the indicators shorts the ignition?

[Rob62]

Neither do I tbh, but i do know that a short circuit or bad earth can cause all sorts of strange effects..... hopefully you will find a simple fix!

[K2-K6]

Picking up on what Rob has said there, about poor earth.

Try running it in the dark with lights off,  then turn the indicators on.  Look carefully to see if you have any glowing in other (non indicator)  lights.

If you can see anything it would confirm the indicators are not fully earthed.  They will try to track out on any other available earth route to establish a circuit.

If you've ever seen cars with all of the rear light cluster flashing dimly when indicating, that's a good illustration.

Check effectiveness of main battery earth too.

[Moorey]

If you still have the buzzer on the indicators try disconnecting the black feed to it.
They are a multi positional switch on US switches the first part of the push should disconnect the feed to the riding lamp in the indicator, at the same time flashing the indicator whilst holding it in that position. When you push it right over then the riding lamp is still disconnected the indicator flashes and the buzzer buzzes.
The black feed to the signal buzzer comes from the same connector as the black feed to engine stop switch.
Got to be worth a try.

[Nigellynch]

some great advice, thank you gents, I`ll try them out over the weekend and post the results.

[Arch stanton]

Well. What happened?

[Moorey]

He found the fault and rode off into the sunset. 

[Arch stanton]

I can't help thinking. When people ask for advice solving a problem on forums.
They should let us know what the answer to the problem was. For the benefit of others. Instead of keeping it to them selves.
Sean.