Zuki 140 2 stroke idle issue

[nautigator]

I have a carbed 140 2 stroke that fires up fine. Within a few seconds, it starts missing and coughs then dies. During the coughing, it puffs fuel/air mixture out from under the #4 carb but I can't see exactly where. I removed the carb plate and looked behind the #4 reed cage. There are no signs the gasket was leaking, or that the reeds are causing the problem. The backside of the #4 carb had tiny scratches or pits in it indicative of something bouncing around between the carb and the reeds. There is no damage to the reeds. I did a compression test and the numbers were fine. The motor was purchased used, and it appears that someone has been through most, if not all of the motor previously. I dropped the #4 bowl off the carb expecting it to be full of trash and found none. I pulled the high speed jet out through the bottom of the carb and it had a small amount of crud right at the top of the threads. Nothing excessive. I am at a loss with what could be the problem. If someone knows, some direction would surely be appreciated.

 

[nautigator]

Re: Zuki 140 2 stroke idle issue

Update: The boat has a pair of these motors on it. I removed the carbs off the known working motor, put them on the other and the problem remains. Also, removing the #4 spark plug and wire eliminates the coughing (fuel/air)issue and the motor runs like it has a dead cylinder (as it should).

 

[Yamajoe]

Re: Zuki 140 2 stroke idle issue

that small bit of crud on your high speed jet suggest there will be more crap in the carbs; i would tear down all carbs and clean them, the spitting fuel could be caused by a stuck open float valve needle/seat.

 

[nautigator]

Re: Zuki 140 2 stroke idle issue

I pulled the power head loose from the center section, chasing the puff of smoke from under the carburator. I found a split in the oil line going from top to bottom feeding the bearings? I replaced the hose, put the engine back together and the problem remains without the puff. I swapped the ECM modules between the motors and the problem remains. All of the coils in each of the motors read the same when tested with an Ohm meter. Since the motor starts, runs fine for a few seconds then shuts down, I am suspecting one of the modules under the flywheel. These are really the last things that could cause the problem. Does anyone have any pointers in testing these components?


Potential Problems eliminated:
Carbs
ECM
Compression

 

[bezerk]

Re: Zuki 140 2 stroke idle issue

what year ?
seeing you have two try swapping this go to brownspoint parts look up dt 140 1992 fig.29 #11-1