Rough Running

[tobro]

Hiya all.

I'm hoping someone can help me please as I've run out of ideas.

My bike is a '78 Z1 which has just undergone a complete engine rebuild including rebore to 1015cc with Wiseco pistons and head overhaul including new valves, guides, springs etc. The coils, condensers, points and plug caps are all new.
On fiirst run up, the bike was running rough which I first put down to carburation issues. I upgraded the standard Mikuni 26mm to a set of fully refurbished 28mm smoothbores (not cheep!). The running improved a little, however, the plugs will soot up within a very short space of time leading to rough running under load almost immediately. I have replaced the plugs but the problem persists.
Could this simply be a jetting problem or would the plugs soot up so quickly due to the higher throttle setting required to overcome a potential misfire due to an as yet unfound ignition fault? I have tried swapping the coils back to the originals but this makes no difference.
Any ideas gratefully received!

[zman]

I have you checked you have a good 12 volts to the coil.
Are all plugs the same

[kz900B1]

http://www.wgcarbs.com//index.php?optio ... =Itemid=89

[tobro]

Plugs are the same (NGK B8ES)

Voltage at coil is 10.6V with ignition on and 11.4V with engine running. ( Battery voltage 12.5V at rest). Low IR in wiring maybe?

Thanks

[z1aphil]

You definitely have a high resistance somewhere. Possibly the "in series" connectors or the kill switch. Something to check is also your grounding. If you have a multimeter with ohms, check from the battery 0v to the engine. this wants to be as low as possible (less than 0.5 ohm). this would indicate a failing earth lead/ connection. You could try and connect your coils + terminals directly to the battery + terminal while you fault find your original problem but do not leave the coils connected to the battery for long without the engine running (same as leaving ignition on without engine running).
good luck !

[tobro]

Great! Many thanks guys-some logical ideas and enough to keep me busy over the weekend.
I'm still hopeful of getting this old lady back on the road before the summer ends!

[zman]

You should expect about 11 volts at the coil without engine running.
When i said are plugs all the same ,i ment are they the same colour

[tobro]

Sorry zman. Plugs are all equally sooty. The bike has never been run for more than a mile at a time.

[Mark Tiller]

What jets are fitted and what airbox/exhaust do you have?

[zman]

with all plugs same color,it could be jets but you need to get voltage to coils at 11 volts before play with anything else

[z1aphil]

Agree with the above comments, we need to know the jet sizes you have and the position of the circlip on the needle.

[z1aphil]

Found this online. Maybe of some use re jet sizes/ settings.
http://www.beezeees.com/resources/carbs ... .aspx.html
Good luck.