Need some help from all Johnson Mechanics

[Pokertrampp]

I have a 1988 120hp Johnson. It has been sitting since last October, and had trouble strating and running. So I was going to rebuild the carbs but i found a set of rebuilt ones on ebay, they looked new to me did not even smell like gas. Well, I installed them and now it runs even worse, according to my manual there is no High/Low speed adjustments on these, is this correct? These are the carbs with aluminum base with plastic body 2 carbs per base/per side. all cylinders have 100+ psi and seem to be getting good spark. so I am fairly sure it is a fuel problem. I am just not sure what to adjust at this point. I have done the link and sync but I am planning to re-do it again just to verify I did it correctly. any advice would be greatly appreciated.

 

[Joe Reeves]

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Comparing the purchased carbs with your original carbs...... Are the embossed numbers on the upper carb bodies the same? Are the throat diameters identical? Are the jet sizes identical and are they in the proper locations off all carburetors?

Curious..... why didn't you simply rebuild your original carburetors?

 

[Pokertrampp]

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Comparing the purchased carbs with your original carbs...... Are the embossed numbers on the upper carb bodies the same? Are the throat diameters identical? Are the jet sizes identical and are they in the proper locations off all carburetors?

Curious..... why didn't you simply rebuild your original carburetors?

I am not home right now, but I will check the items you mentioned and get back to you. also, the reason I bought the carbs was I was afraid the origonal carbs would be really bad due to the new fuel and the boat had older fuel lines and I had heard that the rubber from the fuel lines settles in the carbs and is next to impossible to clean. turns out they were pretty bad, so I was hoping to save myself some work and not have to break out the elbow grease to clean the origonal carbs. looks like I may have to any way.

 

[Pokertrampp]

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Ok, I have rebuilt the original carbs now and reinstalled them. When I try to start it, all it does is act like its going to start but then quits. It will give a quick fire and the starter will disengage but then it shuts back off. I have verified the kill switch is working and the kill cord is plugged in. I think it is some type of adjustment I need to make, but the manual is not very clear on the link and sync so I am not sure if I understand it correctly. I have checked the compression and it is 100+ for all cylinders. Thanks again for all your help.

 

[Joe Reeves]

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Assuming that you have all of the jets in the proper location (those two small jets are different sizes), and you have compression and spark that will jump a 7/16" gap with a strong blue lightning like flame (Snap) with the spark plugs removed, the engine should run. The engine firing will of course cause the bendix gear to disengage.

The proper starting method is:

Pump the fuel primer bulb up hard, apply a little throttle to take the engine off of the dead idle position, turn the key to the start position and push the key in and hold it there to activate the fuel primer solenoid at the same time. When the engine starts, release the key so that it will shut down the primer solenoid.

Is the above your starting procedure?

 

[Pokertrampp]

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Assuming that you have all of the jets in the proper location (those two small jets are different sizes), and you have compression and spark that will jump a 7/16" gap with a strong blue lightning like flame (Snap) with the spark plugs removed, the engine should run. The engine firing will of course cause the bendix gear to disengage.

The proper starting method is:

Pump the fuel primer bulb up hard, apply a little throttle to take the engine off of the dead idle position, turn the key to the start position and push the key in and hold it there to activate the fuel primer solenoid at the same time. When the engine starts, release the key so that it will shut down the primer solenoid.

Is the above your starting procedure?

Yes

 

[Pokertrampp]

Re: Need some help from Joe Reeves and all other Johnson Mechanics

Re: Need some help from Joe Reeves and all other Johnson Mechanics

Yes, it is my starting procedure. also, I did the carbs one at a time and paid close attention to how they came apart to make sure everthing went back in the same place it was removed from.


this was my sync procedure from the manual:


1. Loosen the cam follower screw, move cam follower away from the throttle cam.

2. Loosen the throttle shaft synchronizing screw 2 full turns; making sure the throttle plates are fully closed.

3. Rotate the throttle shaft to partially open the throttle plates, and then let them snap back to the closed position. Make sure they are closed and retighten the synchronizing screw. Leave the cam follower screw loose.

 

[Joe Reeves]

Re: Need some help from Joe Reeves and all other Johnson Mechanics

Re: Need some help from Joe Reeves and all other Johnson Mechanics

Trace one of the small lines that lead FROM the primer solenoid to whatever it connects to..... normally the top portion of the carburetor(s) in back of the throttle butterfly. Pull the hose off that carb fitting and have it aimed away from the powerhead etc.

Pump the fuel primer bulb up hard. Turn the key to the ON position (engine not running). Observe the disconnected hose, then push in the key which should activate the fuel primer solenoid, whch in turn should force fuel to really shoot out that small hose. If it does not, you are in essence attempting to start a cold engine without the excess fuel needed to keep it running until warm.

Let us know what you find.

 

[Pokertrampp]

Re: Need some help from Joe Reeves or any other Johnson Mechanics

Re: Need some help from Joe Reeves or any other Johnson Mechanics

ok, I will try that tonight, and get back to you asap. thanks again.

 

[Pokertrampp]

Re: Need some help from all Johnson Mechanics

ok, I got it running today. it starts right up with no problems now. only thing is it has a miss that is very slight most of the time and then without notice it will be so bad you can see the rpm's slow way down that you think the motor is going to stall, and then it goes back to the way it was. I have checked all the grounds for the coils, replaced the spark plugs. could the cdi be going bad? also i noticed when I rev the motor the miss seems to stay even when I raise the rpm's, no worse or better.