1980 Johnson 25. Another idle issue

[jfitz7]

Hey everyone,
I have a 1980 Johnson 25 with the classic "wont idle unless the choke is pulled". Ive torn the carb apart and cleaned every passage, including all the caps to clean the idle passages. Motor runs great WOT and doesnt skip a beat when you punch it. I just cant seem to get it to idle without pulling the choke. The idle speed needle does not seem to make any difference in how the engine idles. Ive had it all the way in and most of the way out an nothing changes. If the choke is pulled I would assume that it is running too lean but the plugs always appear to be wet. High speed jet has been cleaned as well. Fuel lines are in good condition.
I know these things arent known to idle real well but I shouldnt have to pull the choke to keep it running. Any other thoughts? Thanks

 

[racerone]

Those motors will idle nicely if in good condition.----Is the throttle plate closed at idle ?-----Is that stop on the metal rod ( ~12" long ) set properly ?----Clearly something is wrong if motor does not respond to low speed mixture adjustment.---How did this motor run for you last year ?

 

[jfitz7]

Those motors will idle nicely if in good condition.----Is the throttle plate closed at idle ?-----Is that stop on the metal rod ( ~12" long ) set properly ?----Clearly something is wrong if motor does not respond to low speed mixture adjustment.---How did this motor run for you last year ?

Not sure if the idle plate is closed at idle, havent been able to take the air filter cover off because Ive needed it to hold the choke open to get it to run. I've assumed that the stop on the metal rod is adjusted properly because when ive hit the throttle it revs up just fine with no delay. Is there a certain measurement that it should be at? I just bought this engine, ran fine on the first test run after purchasing but things have been decaying since.

 

[racerone]

Compression test results needed.----Did you replace water pump impeller ?----Mixing gas and oil at 50:1 ratio ?

 

[jfitz7]

Compression test results needed.----Did you replace water pump impeller ?----Mixing gas and oil at 50:1 ratio ?

I'm going to try and get some compression numbers tomorrow. New impeller is on the to-do list although it apears to be pumping fine. Coming out of the tube and the exahust. Gas and oil are mixed at 50:1

 

[racerone]

You need a new impeller.------Your motor does not have a warning or shutdown system should it overheat.-----It would keep running until you notice it slowing down.----Then you would be looking at expensive repairs or another motor.

 

[James R]

Hi guys.
Love these 25Hp motors and you are correct, when in good condition they idle great. Compression test is #1 spark test is #2. These things will idle on one cylinder and from recent experience will also come on line with two with the throttle opened, usually indicating a fuel problem. Ran a service, Carb rebuild, lower unit, the usual stuff. No change.
If compressions are good and the sparks are good, try running the motor at idle and pulling the plug wires off one at a time. Thick rubber glove recommended. This will show if one cylinder is not working. Where are we going with all this you might ask. I found that #2 Cylinder was not running at idle but fine with the throttle open. Aha thought I, lower crankshaft seal leaking the fuel out of the crankcase. Pulled the power head and replaced the seal. No change. After considerable thought I removed the carb and the intake manifold. it then occurred to me that this motor had sat all winter under a Tarp. Sho nuff there stuck in one of the reed valves was a small piece of acorn shell. So the fuel wasn't getting pumped up into the cylinder but back to the carb. With the revs up there was sufficient fuel to feed the #2 cylinder, a little lean perhaps. Pulled the shell out and everything worked fine. Bloody Mice.
This may or may not help but it may amuse you.

 

[jfitz7]

Hi guys.
Love these 25Hp motors and you are correct, when in good condition they idle great. Compression test is #1 spark test is #2. These things will idle on one cylinder and from recent experience will also come on line with two with the throttle opened, usually indicating a fuel problem. Ran a service, Carb rebuild, lower unit, the usual stuff. No change.
If compressions are good and the sparks are good, try running the motor at idle and pulling the plug wires off one at a time. Thick rubber glove recommended. This will show if one cylinder is not working. Where are we going with all this you might ask. I found that #2 Cylinder was not running at idle but fine with the throttle open. Aha thought I, lower crankshaft seal leaking the fuel out of the crankcase. Pulled the power head and replaced the seal. No change. After considerable thought I removed the carb and the intake manifold. it then occurred to me that this motor had sat all winter under a Tarp. Sho nuff there stuck in one of the reed valves was a small piece of acorn shell. So the fuel wasn't getting pumped up into the cylinder but back to the carb. With the revs up there was sufficient fuel to feed the #2 cylinder, a little lean perhaps. Pulled the shell out and everything worked fine. Bloody Mice.
This may or may not help but it may amuse you.

Ha, that’s quite the find! Thanks for the response. I ended up checking compression, each cylinder showing 120 cold. Re-tightened all my fuel lines to ensure no air was being sucked in. Went ahead and pulled the intake off to see what kind of shape the reeds were in. I ended up flipping them over and putting them back. Now the crazy thing idles like a champ. Maybe the reeds were worn just enough to prevent a tight seal on the other side? Who knows.

 

[oldboat1]

Those thin metal valves (leaf valves) should not be reversed, as it stresses the metal and risks breaks. Replacements are about $60 each, and you need a couple of them. I would be looking around for replacements (last ones I bought were NOS versions for a 10 hp -- maybe you can find something like that.) Sorry to be a wet blanket. Run the motor, and look for replacement leaf valves.

 

[jfitz7]

For sure, thanks for the input. Definitely was a temp fix, I was just running out of things to try loI. I will be putting some new ones in soon.

 

[James R]

So pleased to hear of your success.