Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Arch stanton on March 27, 2020, 07:26:15 PM
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Hello Folks.
I have a problem. That I'm hoping someone could help me with.
My 750 is a very good & willing starter normally but..
Last week it started & ran great.
However. Today I gently washed it with bucket & cloth. No hose.
When I came to start it. Push the button. Engine turns over. But nothing. All is dry in the points case. So I put a test plug in number 4 plug cap. And tried the button again. No spark. But if I arc the points with a screw driver. There is a spark.
Has anyone any ideas what could be wrong?
Your inputs would be greatly appreciated.
Thanks in advance.
Sean.
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Dude you wash the handlebars? Wondering if water may have got into the right hand kill switch and cut power to the coils??
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Could just be one of those horrible coincidences, check the points gap and timing
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If you have sparks at points then that verifies the ignition supply side ( switch barrel, kill switch etc) are OK as you are just testing via the earth route.
If the HT leads are in any way suspect with age or condition, just try getting someone else to crank it while you look under the tank in the dark, if they are leaking you'll usually see it sparking across somewhere under there.
It only needs to leak on one lead, for example #4 for it to take out both 1+4 together.
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... Sean, is the battery in a good state - ie is the starter motor robbing the coils of power?
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Good morning.
Thank you all for your thoughts.
James.
I suspected water in the switch too. As when I flicked the lights on. Nothing happened till I tried the switch a few times.
Then they lit up. The switch is a DS pattern part. Not the best I know.
However K2-K6 seems to kill that theory.
Lobo.
The battery is only 10 months old and in good order. However. I have had it on charge over night. So I'll see if it does any better today.
Bryan.
The timing & points should be fine. They were set only 500 mile ago. Also. The bike started & ran the best in has ever run. A week ago.
As fir HT leads. It was dark by the time I gave up messing.
I looked under the tank. Didnt see any sparking.
I know what you say about the leads. When my F1 was my only transport. I cut off the rubber outer sleeve. As the spark would rather travel down between the HT & the sleeve. Especially in winter with salt.
I will tinker again today and will let you all know how I get on.
In the meantime. Please keep your thoughts coming.
Sean.
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First thoughts are that if you have no spark normally, but do when you arc the points, then it suggests the points or wireing to them.
Worth just pushing a bit of fine wet and dry accross the points to ensure they are clean.
Have you checked this effect on both sets of points?
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Hello Seamus.
Thanks for your thoughts.
This morning. I pressed the button and it reluctantly started.
Obviously water had got somewhere it shouldn't. I had forgotten just how susceptible to water the 750 are. Dare not go anywhere without WD40.
Thanks again.
Sean.