GPz750 Pt 2... the colour of sparks..

ok, so the GPz that step son has inherited that wouldnt run properly (titled
no grunt...)...

Carbs stripped cleaned. Not really much in the way of potential trouble can
be seen... jets are clear, floats are mobile and not split, and basicly all
looks ok. Given a good hosing down with carb cleaner and blasted through
from the compressor and all seems hunky dorey. Air mixture screws checked
and re-set.

Now the bugger refuses to start. Battery is fully charged, and plugs new
and correctly gapped. When I remove the plugs and earth them against the
engine casing and turn the engine over, the spark is of a fairly week yellow
nature. Now, IIRC (and I may be wrong) the spark should be big, fat and
blue/white.. Is this correct?... If so, are we looking at a potentially
knackered coil?...

Pointers please people...Coz its getting cold, and my back is protesting at
being bent over this machine all the time!

 

Green, actually. Centre should be purple.

 

Which is precisely the opposite to my experience. I've found they will
quite happily work at lower revs but they break down under load.

...but if the coil feed (earthing IIRC) wires are reversed the timing will
be wrong and it won't start.

 

Yep. Diaphragms all fine and dandy.

Well, it started after mucho hassle and a couple of battery draining
sessions

OK, so this may be a tree Im barking up incorrectly

OK, didnt realise that. Ill double check on all cylinders.

OK, if were still looking at the carbs, what bits to double check? Jets are
clear. Air feed tube to pilot jet seems clear (ie air gets blasted through
it from compressor and I can feel it coming through into main carb body).
Diphragms are intact. Needles are moving freely. Float needle valves all
free and working fine. Float bowls are filling up (checked via drain
screws)... where else should I be checking?...

 

My money is on ignition. How old are the plugs?

 

Check all low tension wires and pay special attention to the
connections. A slight resistance due to corrosion/dirt makes a helluva
difference to the state of the spark. Especially check the wires to the
trigger on the end of the crankshaft.

 

<AOL>

And *then* they refuse to work at all.