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

[Curtis Maglinger]

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.

 

[moparbarn]

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.

 

[Curtis Maglinger]

Great, thx a bunch. I cleaned all the picture and will try this weekend.

 

[moparbarn]

Oh yeah, spark plug gap .018"

 

[larcor69]

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 Rapedius]

Make sure the gasket between the ISO and carb is installed correctly. The pulse hole needs to be on the bottom of the gasket when installed.

 

[Curtis Maglinger]

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?

 

[Gary Murcott]

If you are running an inline gas filter remove it

 

[chad green]

Make sure the gasket between the ISO and carb is installed correctly. The pulse hole needs to be on the bottom of the gasket when installed.

My exact thoughts!

 

[Curtis Maglinger]

What is a ISO

 

[Dan Pralle]

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.

 

[Jeff Schindler]

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

 

[Bob Morton]

HimCurtis,

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

Nails (*¿*)

 

[Curtis Maglinger]

Thx for all the help and recommendations. Cleaning the loctite off and get a better ground fixed the problems. Thx.