Carb adjustment 1975 johnson 50 hp

[batebarnes]

"As per the post yesterday, i

"As per the post yesterday, i have a 1975 johnson 50 horse motor. I need to know the procedureto adjust the carbs, i.e. idle mixture etc. Any help would be greatly appreciated"

 

[london marine]

It only has low speed jets the

It only has low speed jets the high speed jets are fixed.The low speed jets should be out about one turn from gently seated to start adjustments.What is the motor doing that leads you to believe that it needs carburetor work?? Have you done anything else to trouble shoot the motor if it is running poorly???

 

[batebarnes]

"The motor has sat for about t

"The motor has sat for about two years, so i'm thinking that the carb needs rebuilt at least. I wanted to try and see if adjusting the mixture would make it run smooher. It is also fairly difficult to start. The control has a warm up lever on it and the motor will not stay running unless the warm up lever is up. I need to replace all the rubber fuel lines from the tank to the motor. I am a diesel tech and i know that if a diesel engine sucks air through cracked fuel lines,o-rings, etc it will display the same symptoms. Is the same true for a two-stroke. I've changed plugs. I have yet to change the filter as I want to do so when i replace the lines. I also need to check compression. What should my compressionnumbers look like. Thanks for the reply any more help is also greatly appreciated."

 

[joereeves]

"Sitting for two years would n

"Sitting for two years would necessitate the removal, cleaning, and rebuilding of the carburetors in order to avoid having the engine run lean (piston damage etc).

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

When time permits, visit my eBay store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"