GN250 no spark

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

Hi there,

I've put my bike back together but I have no spark from the spark plug, which goes a long way towards explaining why it won't start.

The CDI is getting power on one of the wires and a ground connection on the other. The coil checks out OK - has resistance on primary and secondary.

It ran before the rebuild so I think I must have a dodgy connection or something. I have no idea where to start with troubleshooting it though. Anyone have any experience of Suzuki CDI ignition systems who can help me troubleshoot? Cheers.

taz4626 · Renault 5 Driver Joined: 30 Aug 2009 Karma :

just to clarify how did you check for the spark? sometimes when i have checked for a spark i dont quite earth the thread of the plug well enough so i dont get the spark?

Also are plugs wet with fuel after you have been cranking it over?

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

I touched the tip to the engine casing whilst cranking. No spark.

Also while I was messing about the cap popped off the HT lead. There's a spike inside the plug cap that engages with it so I think it's designed to be removable, I tried stripping the insulation off the very tip of the HT lead and holding the wires from that near the engine block too - no spark still.

rob_scott92 · Could Be A Chat Bot Joined: 28 Mar 2009 Karma :

Does the CDI use the battery to work? If not, it could be the same as the problem i had with the Gs 125, Problem with the field coils. But if it was running and now its not, its likely you may have disconnected something.

Hope this helps in some kind of way haha Laughing

Rob

27cows · World Chat Champion Joined: 01 Nov 2009 Karma :

Will almost certainly be something simple. The kill switch is always worth a double check, as is the ignition switch and its wiring. Obviously make sure the HT lead is firmly screwed into the plug cap (and coil, if it's one that is detachable from both ends).
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

My first port of call would be earthing. Did you paint the frame while you had it stripped? It's possible that the coil isn't earthing well. Double check all connections, if it had some old bullet connectors in places then they may be corroded or the wire may have pulled out of the connector.

I assume it's electric start and the battery is turning it, which means that's ok.

Fuses and kill switch are also an old favourite. If you have time on your hands then checking lots of wires with a multimeter is useful. You might not find a bad wire, but whilst doing all the in-depth poking you may find an obvious problem or a wire earthing on the frame where the insulation has worn away.

Don't go buying expensive parts just yet.

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

Well, I ran a wire from the coil ground direct to battery negative to check it wasn't that, still nothing.

The lead is screwed firmly into both ends.

running out of ideas now. i do have a copy of the wiring diagram but it's not very clear. guess i'll have to chase the wires from the cdi up to the ignition switch (they go there for some reason) and see what's going on.

Also, there's only one fuse. And the killswitch is on, bike doesn't crank without it.

Though I will check the wiring around the killswitch...

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Your local bike shop will have a coil tester, and they'll probably test your coil for a tenner or less.

For an easy test of it, I understand that they charge while a current is applied to the coil and discharge (causing the spark) when the charge is removed. Try running the coil on a direct feed from the battery, holding the plug close to the head, then pulling the positive feed and seeing what happens. Hopefully it'll create a single spark.

Realistically it probably won't and you've need 4 hands.

Bits to check from what I have seen of my CB250RS wiring loom (shudder).

Look for a concealed immobiliser. Someone had put a little switch on mine by the carb to cut the ignition circuit.

Look for an inline fuse somewhere.

Look for any dodgy wiring repairs in the past, like corroded bullet connectors.

Check the coil, pickup coils, alternator, CDI using the tests in the haynes manual. There are assorted tests to check the resistance against them.

The fun bit. Check wires for continuity with a multimeter.

Does everything else (lights, horn etc) work?