1977 25hp Johnson Sneezing

[Harry B.]

I set up the idle jet on my 77 Johnson 25 hp and it idles like a champ.
I ram it wide open for a bit and tried to come back down to idle and it sneezes and backfires for quite a while before it settles back down to idle.
The last time I took it out it didn't seem to want to idle real well again after running it wide open and sneezed and coughed until I gave up (trying to set the idle jet again) and put it back on the trailer.

Any helpful hints or ideas????

Thanks much in advance.

 

[racerone]

Open the low speed jet 1/4 turn and try again. Perhaps throttle plate is opening too early.

 

[Harry B.]

Found it!!
I should have noticed the change in sounds of the motor (louder and a hissing sound of sorts). The lockout lever screw came out. The previous owner disabled the high speed lock out and I didn't pay very close attention to it. Major vacuum leak causing the problems.

Thanks much racerone. I started the low speed idle jet process a couple of times without any luck before realizing what was going on and seeing all of the oil all over the power head. I put a bolt back in it's place and hope that this will take care of it. Again, thanks for the reply.

I just hope it didn't cause any damage to the powerhead/pistons/cylinder walls while I ran it that way.