Duramax 18hp....Idling issues !!

[mrbeggs432]

Need some help...

I have a Duramax 18hp and having troubles with idle...dont know if its a jet/carb issue....

I choke it to start up and set the idle - unchoked.

when I turn it off I have to choke it to start again....even when its warmed up...and even with the idle set kind of high.

Cant really find aftermarket parts for this particular engine....The carb filter and header kit I used were 390 clone parts....no jets

Any help would be greatly appreciated

 

[bob58o]

Clean the carb.
Enlarge the jets.

 

[TT540]

Sounds similar to a problem I just had. The high idle setting was a result of my idle "slow" circuit not working. Check to see if the idle jet is free to flow...
1) remove the idle screw. The one that pushes the throttle blade lever.
2) lift up the black plastic piece below it.
3) lift of the piece below that. This is your idle jet.

The bottom of that should have a hole / passage up into the cross way (larger 1/8" size hole). I had to use air and also a strand or two or wound wire.

If that is free, you can open up the idle needle screw by increasing it's flow some. Loosen = more flow. Or, just go ahead and pull it off and clean it all out. There are some good videos on YouTube for it. The above is an easy dry check that should take 10 minutes.

 

[mrbeggs432]

idle screw/jet ?

Does the piece your talking about come out through the top of carb or internally.....please excuse my ignorance....lol

 

[Nosandwich]

I don't know about this engine or carb, but it seems to me his idle jet is sealed with a plug???

 

[bob58o]

One more piece.
The jet is still sitting there.
Flat tip screwdriver to pry the last part up. Comes out from the top. There will be one or two O-Rings on it. Looks dirty around there.

 

[TT540]

^What he said. The o-ring down in there will make it snug to remove. I pulled mine up with a pair of needle nose pliers.

When you get it out, flip it over and do this to it: