1984 Johnson 25hp Backfires & Stalls

[speedingsilverbullet]

Hello everyone,
I have a 1984 Johnson 25hp that I'm trying to get back in good running order. The motor has a funny problem being that when you are at an idle in forward and you give it some throttle quick and then go right back to idle it will backfire and stall out. It will sometimes randomly do it, without the quick throttle motion, when you are just idling in forward gear. Adjusting the low speed doesn't help the situation either. The carburetor has just been gone through, float level is set properly, Compression is 122psi on cylinder#1 and 129psi on cylinder#2. I have indexed the flywheel and checked for erratic ignition which is looking good. I tend to think its a fuel problem but I would think opening the low speed adjustment would remedy the situation if that was the case. Does anyone have any suggestions as to where I should go next?
Thanks in advance.

 

[racerone]

Re: 1984 Johnson 25hp Backfires & Stalls

The long rod that goes to the back of the motor possibly needs to be looked at.--------Folks sometimes adjust it so that throttle opens too early.----Move the adjusting collar forward 1/8" and see if miss goes away.

 

[speedingsilverbullet]

Re: 1984 Johnson 25hp Backfires & Stalls

I moved the collar forward and set the roller/cam to the repair manual specifications. The problem seemed to go away until the motor warmed up then it came right back again. Could it be one of the crank seals expanding from the heat and allowing a lean condition on one of the cylinders?
I'm stumped..
Thanks in advance

 

[joeseif]

Re: 1984 Johnson 25hp Backfires & Stalls

Did you set the ignition timing, as far as the roller for the carb?