TOPIC:

Hi all,
Just bought my first KZ1300, always wanted one of these beasts when I was younger but couldn't afford it back then! registered as 1980 imported into UK 1998, 16000 miles, ran sweet on trial run of about half a mile, now the 2 middle cylinders won't fire up, been on a 15 mile run up to 8 thou revs, still not firing, exhaust pops at times, before I strip the carbs or start checking the coils etc, any help would be much appreciated.

Many thanks
Nigel

PS
I WILL BE ON HOLIDAY UNTIL THE 17TH JULY, I WILL RETURN MESSAGES THEN.

An oil fouled plug could kill 2 cylinders since it's a dead short to ground. (#3 or #4)
Bad coil that services plugs #3 and #4 (same coil)
Stuck float (closed) on center carb. Open the drain and see if it flows.

But since it's back firing if out the exhaust that's raw gas burning in the exhaust which leads me to believe it's an ignition problem. Backfiring through the carbs would be a tight valve.

Lots of things to check.

Kawboy wrote: An oil fouled plug could kill 2 cylinders since it's a dead short to ground. (#3 or #4)
Bad coil that services plugs #3 and #4 (same coil)
Stuck float (closed) on center carb. Open the drain and see if it flows.

But since it's back firing if out the exhaust that's raw gas burning in the exhaust which leads me to believe it's an ignition problem. Backfiring through the carbs would be a tight valve.

Lots of things to check.

I think I need to post a correction here. Had the cylinders been firing in a parallel circuit, it would be possible for one oil fouled shorted to ground plug to absorb all the spark, but I had forgotten that the wasted spark setup has the one plug firing in straight polarity ie. voltage leaving the negative side of the coil and traveling done the high tension lead through the plug and to ground AND THEN, hard to believe but the spark travels through the ground source (engine block) and then flows through the other plug that's associated with the coil that fired in reverse polarity ie. the spark jumps from the side electrode to the center electrode and up the high tension lead and back to the coil positive terminal on the secondary side. So the center electrode will burn one of the plugs, and the side terminal will burn on the other plug associated with the same coil. The latest news for those who may not know is that the sparkplug manufacturers are advocating that double platinum or double iridium plugs be only used in wasted spark systems or spark plug changes at 30,000 miles rather than 100,000 miles due to this abnormal electrode wear.

My apologies to all for the misinformation previously posted.

Thanks to everybody's posts,
I started work on the z this evening, started with changing the plugs, firing on all 6 cylinders again! The middle carbs leak fuel out the back when not running with the petrol tap on, I will take her out for a spin tomorrow eve to see if it clears itself, I have been told it's worth buying iridium spark plugs rather than standard ngk's? Also change the standard petrol tap? The tap I have is not vacuum as it has only 1 pipe out the back, the previous owner done little more than ride it to the mot and back for several years so I'm teething out the issues to get her reliable.

Nigel