Johnson cd-12 5.5 low speed idle problem

Tech Tony

Petty Officer 2nd Class
Joined
Apr 30, 2016
Messages
105
Hi all, I have been working on this motor for 2&1/2 months and I finally have it ready to run. I started It today, and It really wants to run,...but..while it runs good at start and above, after some adjustment, It really runs good, but if you drop below start, it dies. As soon as the lever on the carb no longer touches the cam on the magneto plate that's it, game over. I admit that I really don't know how to adjust the carb, I tried using the instructions on duckworks, you know, one and a half turns out for the low speed idle needle, and one turn out for the high speed idle needle, to begin, but none of the instructions after that to work..I did notice that it seemed to run better as you closed off the low speed needle, but it bottomed out before it got where it needed to be. I don't know if its a timing issue either. I set the points at.020 through the hole in the flywheel, but I don't know if that's the right way to do it... I feel that I am close, but cant close the deal due to lack of expirence . I rebuilt the carb last weekend, and it has all new o rings, washers, seals and gaskets and a new ethanol proof float. And new low and high speed jets. I got 77 psi on top cyl. and 80 on bottom with a good snap on gauge. Its almost like the positions on the throttle are off, but that dosn't seem possible. I know there is someone out there that has seen this before. I will appreciate any input....thanks in advance....Tony
 

nabiul

Petty Officer 2nd Class
Joined
Jul 18, 2015
Messages
131
The lever on the carb should always be touching the cam on the magneto plate. You need to calibrate the throttle linkage to the spark timing, aka link and sync.
The cam should have a little mark on it near the beginning when it's at idle, basically set the lever so that it is touching this mark when the throttle is at it's lowest.
 

Tech Tony

Petty Officer 2nd Class
Joined
Apr 30, 2016
Messages
105
Ok, I see what your saying, So I adjusted the cam plate to where the whole length touches the card lever. It is not long enough to touch when it is on the slow setting, but is is touching on the shift setting now. It will most likely run better tonight when I try it, but If any one can help me adjust it properly I will greatly appreciate the help.
 
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