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1994 Johnson 15hp idle issues

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Bill Krummel

New member
I picked up a 15hp Johnson this week and can not get it to idle. The carb was in pieces when I got it with the adjustment screw pulled out so I have no clue where the setting was last time it ran. The main problem I'm running into is when I try to run the adjustment screw all the way in the spring binds before the screw bottoms out. If I give it just the smallest amount of throttle it runs fine, and if I use a screwdriver to open the throttle butterfly on the carb I can almost get it to idle but it seems to lose everything when I bring it down to a low idle. Im not sure what rpm I'm turning but I tend to like a low idle on my engines. Does this sound like an adjustment issue or am I fighting with larger issues?
 
Step #1 is always a compression test.----Post the actual numbers here.----If those are good then more tips will be posted.
 
Compression read 110 on top cylinder and 105 on bottom. I played with it some more today and got it running good untill I put the cover on. When I put that cover on it loads up and dies.
 
Problem seems to be fixed! After my last post I started thinking, if putting the cover on makes a difference it must be getting air somewhere it shouldn't. I began to disassemble and pull the carb and I quickly found i didn't torque one of the carb bolts, as well as a leaky fuel line. I also clean the carb again and found some trash blocking the low speed orifaces on the top of the carb. After reassembly it seems to be idling and running great! All this headache because I did pay good enough attention on the initial assembly. I will update again if tomorrow morning the problems resurface.
 
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