68 Johnson 20 horse idle...

[Thor80]

Hi All,
I'm working on a 68 johnson 20 horse for a friend of mine. We got it all up and going, starts nicely on first or second pull. Havent run it out on the water yet but in the barrel the only issue we have is idle. It runs decent but a little rough at the "high idle" (being the neutral mechanical stop) and when i unplug the fuel line going to the gas tank to run it out of fuel after 10-20 seconds it smooths right up and runs at a higher rpm than it was and a few seconds later it dies out because i unplugged the tank. What are your thoughts? Tried to get a carb rebuild kit last weekend but they gave us the one for a '69 and it didnt work so we'll try again soon. Try carb rebuild, fuel pump, maybe something with the gas can? Any thoughts would be appreciated before we start throwing money and parts at it.

-Torsten

 

[ClassyGlassy]

Re: 68 Johnson 20 horse idle...

rough idle until you disconnect the fuel line suggests that your low speed orifice is the wrong one! Take it out and try to get a smaller Low Speed orifice.

Start there and let me know what you find.

Paul

 

[samo_ott]

Re: 68 Johnson 20 horse idle...

Yes. If it smooths out just before dying, this is a lean condition. Try adjusting the low speed needle. If not, rebuild the carb. It's quite easy.

 

[lindy46]

Re: 68 Johnson 20 horse idle...

Yup - clean/rebuild carb and replace the fuel lines.

 

[Thor80]

Re: 68 Johnson 20 horse idle...

Thanks for all the responses! Yea we're gonna try to get the right kit and rebuild it soon. I'll check that low speed needle. After it was suggested i thought back and i think that the needle from a '69 parts motor was put into the '68 carb because it "looked" better. I'll switch it back or we'll try to get a new one with the rebuild kit and i found the directions in the Top Secret folder to make the initial adjustments on that needle which we didnt do before. Anyway thanks again!

-Torsten