Logo
FULL SITE MENU

High fuel consumption, rough idle

S

Scod

Member
Hi guys, my 1982 Johnson 140 J140TLCNB is giving me grief. It's hard to start, doesn't want to idle in neutral but will idle in gear. Won't idle on muffs, it backfires and dies. Acceleration is poor but it will get up and go and seems to run ok, tops out at around 35mph. One spark plug is not oily, it's dry and cleaner than the others. I've just swapped the coil with another cylinder to see if the dry plug is caused by a bad coil.

I was blowing power packs and dropping a cylinder so took it to the shop to diagnose the electrical system, they found a broken spark plug lead to be the culprit. Everything else tested ok.

I checked reed valves which all looked like new.

I have a new fuel tank and primer bulb. Fresh fuel.

I rebuilt the top carb when chasing a fuel leak. Both carbs are clean. I opened them up today and noticed that while the top carb float is set correctly (I think, parallel with gasket when held upside down), the bottom carb has the float at an angle. See pictures. Also in the video you can see that when I cover the hole at the top of the carb and squeeze the primer bulb it squirts out fuel. The bottom carb will not squirt out fuel.

Is it misfiring because the bottom carb float is set too low and it's running lean? Or is the top carb float set too high and it's overflowing? I don't know whether it should or shouldn't be squirting fuel when I squeeze the primer bulb. Will post pictures and videos below.

https://youtu.be/upe-fnSUJKY
 
Seems to run ok at WOT ... carb settings - parallel with the gasket when upside down is not necessarily the correct setting .... you would need to get the exact setting from a manual and set it with a depth gauge .... but from what i can see it def needs a tuning, including the air/fuel mix.
 
Scod said:
I rebuilt the top carb when chasing a fuel leak. Both carbs are clean. I opened them up today and noticed that while the top carb float is set correctly (I think, parallel with gasket when held upside down), the bottom carb has the float at an angle. See pictures. Also in the video you can see that when I cover the hole at the top of the carb and squeeze the primer bulb it squirts out fuel. The bottom carb will not squirt out fuel.
Click to expand...

Rebuilding one set of carbs and not the other is not advised. If you're going to that trouble you should run through them all.

No, fuel should not squirt out like that. you definitely have one or more floats that are not sealing.

Did you use brand new needles and seats?
Did you go completely through the carb cleaning all passages and using all new parts supplied in the kit?

Correct float level is NOT parallel to the carb body. if you hold the carb upside down, the end opposite of the hinge point should be angled up ever so slightly.

KJ
 
Thanks guys

Kevin, I only did the one carb because the fuel leak appeared to be coming from the top carb (turned out to be a hose). I installed all new parts. When I hold the carb upside down and blow in the fuel inlet I have a good seal, so I think the needle is ok.

On the bottom carb when I have it upside down the end opposite the hinge is angled up.
 
I chucked the carbs back on and the difference is substantial. First thing I noticed is how much faster it was idling. I had to adjust the cable as well as the screw to get it idling right. It's also so much easier to start.

The backfire/sneeze/misfire whatever it is isn't completely gone but it's significantly better. I'm looking forward to putting it in the water and seeing how it runs and if my fuel economy has improved. Here's a video of it idling.

https://youtu.be/UIAn7d6WfH8

I can't remember if it blew that much smoke though, does that look normal?
 
Some more final adjustment with the carbs, another few cleans (",) .... I use to never understand how clean you can actually get a carb until I bought myself a ultrasonic bath, it is great, makes such a big difference!
 
Back
Top