Help with CBR electrical system.

[Weaselman]

Nailing togeather a CBR 400 and it seems to have a weak spark. (Small white jumping sparks rather than a healthy blue/purple spark that can jump from the diode to a metal surface)
I have:
Put new plugs in. Correctly gapped.
Checked resistance of the coils. Both 3.5 oms.
Checked resistance of leads. About 5.3 on a 20k setting which is ok for copper core.
Bike has sat for a loooong time. Carbs are rebuilt and get fuel but I can't even get the bike to cough.
Starting on a fully charged battery.
I suspect CDI but because the engine wont start I can't check reg/rec or stator output..

Suggestions?

[Hillsy]

Are you sure the engine is getting fuel? I rebuilt a set of carbs on a FZR250 a while ago and even though it had a fuel pump and the bowls were full it needed a hand over the carb inlets to "prime" it and help it fire up.

[Weaselman]

Yep its getting fuel. Can't even get a fart out of it with aerostart.

[M.V.]

Well, it's a Honda, dodgy earth or rec/reg? Or both?

[Hillsy]

Check the ignition pick-ups and associated wiring.

If that checks out then yeah - it's probably a toasted ignitor unit.

[Hillsy]

And do a stupid check on side stand / clutch switches. You never know....

Also - have you changed out the ignition switch? Some of them had a resistor in them that would disable the ignitor. They'll crank over but not fire.

[hyofighter]

bad earth maybe , supply your own earth direct from batt see if it helps ,

[Weaselman]

Starting to think its compression. Going to leak down test it tomorrow after speaking to Harley at RB racing.

[slingy88]

Leads on right plugs? I got caught out as a young fella on a cb125 twin. Tried everything to get it going. Spark, fuel, good battery but nothing other than lots of swear words. Then after a cuppa, I realised the obvious, swapped the leads around and fired straight up lol. Some lessons never forgotten aye!