Zenoah 260 Pum 257 carb - after half throttle it cuts out bad

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Curtis Maglinger

Well-Known Member
Joined
Aug 8, 2006
Messages
218
Ran motor/boat for first time and ran great at half throttle, then cuts out real bad till u go back to half throttle. Changed carb and didn't help, changed plug and it helped. At a loss any help is appreciated.

High needle is 1 turn out and low is 2 out

Running Coleman fuel with oil.

Thx in advance.
 
Check the gap on the primary coil, set it at .012"-.016". Also check the ground on the secondary coil, may want to run a ground wire. You didn't use loctite on the coil mount screws, that can cause coil grounding issues. I had a similar issue, turned out to be the prop! After half throttle, the engine just went "flat", but not missing. Different prop, happy engine.
 
Everything Robin said ,Also, check your pipe's length, could be too short, start around 13" or a tad more then work your shorter from there once you get her runnin good
 
Randy, what is ISO? I looked at the gasket between the carb and case and my gasket has 2 small holes....top and bottom. Is that good or bad?
 
It's the block that is in between the carb and the cylinder. There is a gasket on both sides of it. Make sure it is tight to the cylinder and then all the holes line up when you put carb on.
 
Bad coil can do this, not sure why

Air leak like carb / ISO gaskets can too

Bad carb diaphram, but you changed that.

spark, air and fuel
 
Last edited by a moderator:
HimCurtis,

Check the O ring on the exhaust headeder. Take out the isolator plastic block replace with an aluminum block.

Nails (*¿*)
 
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