Johnson 35hp 3 cylinder will not idle

[riverrunner22]

I have a 20?? Johnson 35 3 cylinder 2 stroke that will not idle. i pulled the carbs and cleaned them so i know that's not it. I am not familiar with this motor. On my yamaha i can adjust the idle with an idle screw that opens the butterflies. I dont see that on this motor. When the throttle is closed, all 3 butterflies are closed all the way. Is it supposed to be like that?

The motor will run as long as i keep pulling the choke or keep it in the mid to high RPM's, just wont idle.

thanks for any help!

 

[riverrunner22]

Re: Johnson 35hp 3 cylinder will not idle

also, anybody know how many turns out to set the mix screw on each carb? thanks!

 

[Cofe]

Re: Johnson 35hp 3 cylinder will not idle

Rough setting is one and a half turns out. In is leaner, out is richer. Fine adjust one carb at a time. Do not try to fine tune them equally at the same time.

 

[riverrunner22]

Re: Johnson 35hp 3 cylinder will not idle

Any idea why it won't idle. Mix screws are correct.

 

[Daviet]

Re: Johnson 35hp 3 cylinder will not idle

Usually if you have to use the choke to keep an engine running it means the low speed circuts in your carbs are plugged. You need to post your model number so that we know what carb to look at. Have you checked the compression and spark, both can cause idle problems.

 

[riverrunner22]

Re: Johnson 35hp 3 cylinder will not idle

Compression is 130,115,130, top to bottom. 99 johnson 3 cyl 2 stroke pre mix 35hp. If it will idle with choke, that makes me think the spark is good. Carbs are clean.

 

[Daviet]

Re: Johnson 35hp 3 cylinder will not idle

Compression should be ok. Your thought about the spark is correct, so that means if you have to use the choke to keep it running you must have a fuel problem. When you overhauled the carbs did you blow out the low speed circuts with compressed air?

 

[boobie]

Re: Johnson 35hp 3 cylinder will not idle

If you have to use the choke to make it idle it sounds like a carb prob to me too. It's always the little things in a carb repair that will get you. ALL the passages in the carb have to be clean.

 

[Snowfish]

Re: Johnson 35hp 3 cylinder will not idle

Has to be a plugged jet. On the third cleaning, of my snowmobiles carbs, I resorted to the taboo "poking the wire through the jet" process. There was clear varnish on the jet walls. Carb cleaner shot through ok. Compressed air worked good. But still just a little varnish remained. Those babies are frog hair small! Just a little crud makes a huge difference.

 

[riverrunner22]

Re: Johnson 35hp 3 cylinder will not idle

i completely took apart the carbs, soaked in chem dip, rinsed, then blew out all passages with my air compressor. i've cleaned 40-50 carbs in the last couple years. the only thing i didnt do was install new gaskets. they looked good, but who knows, maybe they arnt. i told the owner to order a carb rebuild kit and we'll go from there. if that doesnt fix it, i guess i'll look harder at the idle jet even though they looked clear to me. thanks for all the help fellas!