Johnson 9.5 dies at low idle

[ltspecial]

1969 Johnson 9.5, rebuilt carb, new fuel pump, gas tank pickup screen etc. is fine. Engine starts fine, runs great at mid to WOT. But trying to get it to idle down to trolling speed (in gear or in neutral), it will start to hiccup and misfire and die. I pulled out the low-speed needle and it had just the tiniest of scoring, but it really looked ok. I reset it and tried all settings for it but still the same.<br /><br />Here's the kicker. I can get it to stay running in a sort of fast idle if I pull out the choke *just a little*. Hardly moves the choke plate at all (I'm guessing there's something else going on there but I can't see it). But that's still too fast for trolling.<br /><br />I changed the plugs but still the same. The plugs do come out fouled (wet) so it does look like some sort of mix problem.<br /><br />Any suggestions?

 

[rickdb1boat]

Re: Johnson 9.5 dies at low idle

Sounds like you need to get back into the carb and clean it again. It only takes a speck to throw everything off. Make sure the float is set correctly, too. Has all the indications of a carb that needs attection, even though you rebuilt it. Make sure to blow all the passages out with compressed air if you didn't before..

 

[R.Johnson]

Re: Johnson 9.5 dies at low idle

This could also be caused by the carb opening to early. Reset the throttle shaft pick-up point. This is done where the throttle shaft roller ride's on the mag plate cam.

 

[ltspecial]

Re: Johnson 9.5 dies at low idle

I was looking at the section in the manual explaining how to the set the pick-up point, but it's as clear as mud (and the typeset is messed up too). Any chance of getting a simple how-to for the process? Thanks.

 

[Paul Moir]

Re: Johnson 9.5 dies at low idle

I'll try to clarify:<br />The carb's throttle valve (butterfly) should just begin to open when the little lever that operates it is between the two marks on the cam bolted to the armature plate, underneath the flywheel. <br />If there is only one mark, then you must adjust it so that the throttle valve opens when the mark is in the centre of the little lever. <br />You adjust the opening point by loosening the screw to the right of where the rich/lean cable comes into the carb and moving the lever.<br /><br />I hope this helps a bit!

 

[ltspecial]

Re: Johnson 9.5 dies at low idle

Thanks folks, it appears that resetting the pickup<br />point was the answer. I messed with the lever screw and it didn't seem to do a whole lot of adjusting, but I guess it didn't need much because now the engine idles fine and doesn't conk out. Paul, thanks especially for the extra explanation, that helped a lot.<br /><br />This forum is a terrific thing, I hope I can return the favor to someone else in need someday. Thanks again.<br /><br />Russell