Thin/weak spark

[DomP]

Im beginning to question the strength of the spark I'm getting, its very thin rather than fat, coils all test ok and new leads and resistor caps, full battery, other than connections what could cause this?

[deltarider]

It depends. A simple test is to first isolate the breakerpoints, connect a wire as shown in the pic and then 'brush' the other end of the (stranded) wire over the engine. A connected spare sparkplug in firm (!) contact against the engine should then show a serie of sparks, much brighter than just one turn of the crank can cause.

[DomP]

I'm running a dyna s electronic ignition currently as it came with the bike.

[deltarider]

What problem do you experience? Having a 'modest' spark by just cranking at which the coils+ will have no more than say 10V is not really a problem. When revved the coils+ will have 14V and that's a different story.

[DomP]

Im not sure it is a problem to be perfectly honest, I'm chasing a bit of a running problem that may well be my lack of understanding.   Basically I have rebuilt every from engine to carbs (cb550f with all stock 069a keihin jets set to factory and airbox with Delkevic 4 into 1) but struggling to get a smooth ride, once warm it will bog down then race away which I wonder could be the advances along with running a bit rich. 

At idle it isnt possible to hold 3k revs, idles lovely at 1k, bit of throttle and it will rise but just around 2.5k it jumps to 4k.  It'll happily drop again so not a hanging idle that I had when the inlet orings were the wrong size.