1969 johnson 20hp idle issues

6

67-69johnman

Petty Officer 3rd Class
Joined
Feb 17, 2012
Messages
75
im having an idle issue with my motor. problem being it wont.
i just put a carb kit in it.
it will run while holding the throttle open but it wont idle on its own, i could remember the needle setting exactly so i set it 1 1/2 turns out and tried setting it while running but just couldnt get results.
school me its been a while thanks guys
 
lindy46

lindy46

Captain
Joined
Nov 27, 2008
Messages
3,886
Re: 1969 johnson 20hp idle issues

Did you remove the welch plug from the top of the carb and clean the idle circuit beneath?
 
D

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1969 johnson 20hp idle issues

Is the spark and compression up to spec?
Link and synk set properly?
 
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O

OptsyEagle

Lieutenant
Joined
Sep 13, 2006
Messages
1,359
Re: 1969 johnson 20hp idle issues

Not sure what you mean by "not getting results". Run the motor with it at the 1.5 turns out from seated. Let it warm up. Reduce the idle to as low as you can. It will probably run rough. Now turn in the adjust (clockwise) 1/8 of a turn and give the motor 10 seconds to respond. If the idle increases, decrease it back down to the lowest you can and turn the dial in another 1/8 of a turn. Keep doing this. At some point the motor will cough and hiccup and want to die. Turn the dial counter-clockwise 1/4 turn and leave it there.

Now at this point is should be idling fairly low. If it still requires a fast idle (and even if it doesn't) verify the link and sink is correct. I am not sure how it is done on your motor but the timing advance needs to by synchronized with the carburetor to ensure your spark is firing at the correct time. Once the carb roller moves off the throttle cam the only thing controlling your idle is the retardation of the timing of the spark. So this can play an important role in the lower idle RPM ranges.

If that is set and you still can't get a low idle, you may need to relook at cleaning that carb again, focusing on the slow speed jet and under the welch plug.
 
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6

67-69johnman

Petty Officer 3rd Class
Joined
Feb 17, 2012
Messages
75
Re: 1969 johnson 20hp idle issues

well i at least got the setting straight. i did pull the welch plugs and it looks brand new inside. compression is 125 in both cylinders and i just put new points and condensers on set to .020 and we have a nice 3/8 bright blue spark. finally got it dialed in last night at about 1230. the problem "i think" was the float i didnt even think of it when i pulled it but it was way off i think the fuel air mixture is correct now. the only thing is the low speed jet is very sensitive now i seem to remember having more leeway with that knob but its about an 1/8 th of a turn either way is too much!
 
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