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SOHC.co.uk Forums => CB500/550 => Topic started by: Tonyh on July 04, 2021, 11:06:54 PM

Title: No spark at plugs (CB 550 f2)
Post by: Tonyh on July 04, 2021, 11:06:54 PM
Hi all, new wiring harness, new coils, new battery, new fuse box, all lights work (inc. instrument lights) and all earth points are ok but no spark at the plugs. I'm no electrical genius, so what am i missing, what wires are wrong / not connected and where do i start looking. This bike was running before i bought it !.
Cheers, Tony.
Title: Re: No spark at plugs (CB 550 f2)
Post by: Bro550F on July 04, 2021, 11:52:19 PM
I'd start by checking the wires/connectors from the points to the coils. Then the wire from the kill switch and the Ignition switch.
Sorry not at home or have diagram at moment, so can't tell you the colours.
Title: Re: No spark at plugs (CB 550 f2)
Post by: K2-K6 on July 05, 2021, 08:50:59 AM
Switched on, do you have power to the coils? If not you need to track through to find why that's not there. The route is from battery through fuse,  connecting in headlight to then go through ignition,  kill switch and to the coils.

Then, blue and green wires ( I think are the colours) from coils go to the points which are the earthing route.

When the points are open you shoul have no earth conact,  if you do then you need to make sure all of the insulation washers etc are in place where the wires are bolted to the points, any wrong placement here will stop them switching the coils to make sparks.
Title: Re: No spark at plugs (CB 550 f2)
Post by: Bryanj on July 05, 2021, 08:54:46 AM
Blue and yellow coils to points and for some reason they always seem to disconnect in the boot by the rear brakelight switch
Title: Re: No spark at plugs (CB 550 f2)
Post by: andy120t on July 05, 2021, 09:27:33 AM
Did you put the fuses in?!
Title: Re: No spark at plugs (CB 550 f2)
Post by: hairygit on July 05, 2021, 09:42:02 AM
I assume the kill switch is in the "Run" position? (Certainly wouldn't be the first on that one!)

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