One cylinder not cutting out

Se3e thats why i think its the carb, the piolet screw has no affect no matter how far ZI turn it out or in. Darn thing just wont fire unless I give it throttle. Even if there was a leak in the boots the fuel would still ignite if i was turning the pilot screw to enrich it.

KZCool wrote: the piolet screw has no affect no matter how far I turn it out or in.

This is generally a good indication that there is a clog in the pilot mixture circuit (either in the carb itself or the jet), or an air leak is present.

Turning the mixture screw closed should cause the engine to stumble, and also at some number of turns out.
A significant air leak can prevent proper vacuum from picking up enough pilot mixture - hence no start.
Could be that your idle input (thumbscrew) is not set correctly as well - like too little, or far too much idle to compensate for another issue.

Many different things can affect proper carburetion - best to pull them, clean them like new, confirm that cleaner will blast properly throughout the carb thru holes into its bore, set the slide gaps as close as possibly the same and set base idle opening to about 1mm. Make sure to seal everything up good when reassembling.
Take car to make sure everything is set to baseline specs as per manual. Including timing and such. - basic maintenence.


Good luck.

I Took my carbs back off the other day and have had them soaking in a pinesol solution. I went ahead and checked the intake manifold gromet and it was loose, so there was deffinitely a vaccume leak.

So I reserecting this forum because I have given up on my kickstart and rebuilt my starter. The starter system works good and will work like new when my battery gets here, but the one cylinder still wont fire. It wont fire even when I open the throttle. It has spark, checked the compression and both were at 15 cold so I figure about 130 hot, and the plug is when from fuel when I pull it. The bike does die when I pull the cap off of the sparkplug even though that cylinder isnt firing. Tinking about just getting a new coil. Is the 3 ohm Dyna ok to use with a Dyna S ignition?

KZCool wrote: ...the one cylinder still wont fire. It wont fire even when I open the throttle. It has spark...bike does die when I pull the cap off of the sparkplug even though that cylinder isnt firing. Tinking about just getting a new coil. Is the 3 ohm Dyna ok to use with a Dyna S ignition?

Plug wire might be shorting to engine or chassis (typically happens with old hard cracked worn-out spark plug wires). Z1E also list the Dyna plug wires with caps already built in. I have enjoyed Dyna's solid copper core versions for many years.

Valve clearances within specs?

Would test compression both wet and dry, to compare.

Green 3 ohm Dyna coil is fine with Dyna-S ignition.

Good Fortune!

KZCool wrote: ... one cylinder still wont fire... bike does die when I pull the cap off of the sparkplug even though that cylinder isnt firing....

Engine dies when the secondary loop is interrupted, because neither plug fires under such condition.



If tested with a known good spark plug attached to the cap and plug's base grounded against engine head, and spinning or kicking the engine over with the ignition switched ON -- are sparks visibly observed at tip of the plug?

In other words, is it for sure that a good plug is firing, as contrasted to a cylinder that isn't firing?
(Sometimes a cylinder won't fire despite plenty of plug sparking.)

Good Fortune!

Old hard cracked worn out spark plug wires may permit this to happen:




Or an internally shorted spark plug might be allowing conductivity through the secondary loop even though the plug itself isn't sparking.



Good Fortune!

KZCool wrote: ...76 kz750 twin...dyna S ignition....

Perhaps could elaborate about the Dyna-S on a twin.

Good Fortune!

I wasnt realy sure what you were asking about the plug, but yes it sparks when I hold it to the head. And for my ignition, I just used a single switch to my stock coil to make it fire. I wired the second to my brake light so it flashes with my rpms. Just thougt itd be cool. Only problem is that the stock bulb isn't made for blinking so the filament doesnt have time to dim between crank revolutions. Have yet to find a suitable replacement..........I just went out to double check myself and It's a bad plug :S boy do I feel stupid haha.