64 9hp Runs bad

[eggbert55]

Father-in-law bought a 1964 9hp that had a old bad gas problem. I rebuilt the carb and fuel pump and cleaned out all the fuel lines. Now it starts and runs with the choke closed but when I open the choke it dies. Any ideas what to do next????

 

[JB]

Re: 64 9hp Runs bad

Model number? Or are you leaving off the .5? I will treat this as a MQ-10, 9.5HP Johnson.

Sounds to me like an unsuccessful carb overhaul, eggbert. My suspect would be the orifices in the throat of the carb not being clear.

Other suspects might be a failing fuel pump or air leaking into the fuel line.

What happens if you pump the primer bulb when you open the choke? Spray fuel into the carb when you open the choke?

An air leak into the crankcase might also cause that, but that would be rare.

Let us know what you find, and clarify the model number.

 

[eggbert55]

Re: 64 9hp Runs bad

It is a 9.5 model 9422.... recleaned all passage ways in the carb, new needle and float... fuel pump rebuilt and pumps fuel.... primer ball is hard and doesn't change the engine speed if squeezed while it's running.... sprayed fuel into carb while opening the choke but still dies.... while it's running with the choke almost closed all the way if I turn the lean idle screw in or out you can hear the rpms change.... also sprayed carb cleaner all around carb gaskets while it was running, no rpm change.... any idea's

 

[JB]

Re: 64 9hp Runs bad

How did you access the orifices in the carb throat?? Did you remove the plugs opposite? Are the replacements tight??

 

[jbjennings]

Re: 64 9hp Runs bad

I would check spark with a SPARK TESTER to see if the spark will jump a 1/4" air gap with a good blue spark. Those coils are notorious.
Intermittent spark or spark on only one cylinder can really resemble a carb problem sometimes.
Usually dirty carbs will run with the choke closed, but not open. Opposite of what you describe, which is why I suspect spark problems, along with the fact that those old coils will almost invariably need changing if original.
Good luck,
JBJ

 

[eggbert55]

Re: 64 9hp Runs bad

A little confussed on the orifices in the carb throat.... looked at the diagram of the carb on MarineEngine and the only thing they call an orifice is at the bottom of the float camber??? Do you have a link to a diagram that will show me what ur talking about or can you explain it better????

 

[eggbert55]

Re: 64 9hp Runs bad

Well my shade tree may not be as big as your's...lol lol... but it does run with the choke closed and dies if I open it up more than a 1/4 of an inch.... have checked the spark and it is good...

 

[F_R]

Re: 64 9hp Runs bad

You can almost bet the farm that you didn't clean that orifice plug in the bottom of the float bowl. Did you? It must be absolutely, positively squeeky clean, without even a trace of any dirt, varnish, or gum in it. And don't go jamming wires and stuff through it either---oversize is as bad as dirty. It is a highly precision orifice in that thing.

 

[eggbert55]

Re: 64 9hp Runs bad

No I didn't... so we talking about just carb cleaner and compressed air to clean it.....

 

[eggbert55]

Re: 64 9hp Runs bad

Ok guys cleaned out that orifice with carb cleaner, now have a good stream of fuel going... engine starts and will now rev up but still is running rough, seems to have a little back pop or clunking noise like it wants to die.... is it time for a tune up like new points and coils???