1984 Johnson 50 hp carb question....
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Posted on Tuesday May 22, 2012 at 2:37 PM  
Having some problems with my motor.1984 Johnson 50 hp (J50TLCRM) It ran good last year, but not "great", would die sometimes while idling. This spring, motor ran bad. Here is what has been done so far to help remedy it. New gas tank and hose,new clamps on all fittings, cleaned and put carb kit in, new plugs. Replaced starter solenoid (unrelated, but figured I'd mention it) Still, has very rough idle, but runs great at high rpm's. Also, runs great on muffs, but not water. Now, I am not a HUGE mechanic at all, more of a parts changer! What I'm unsure of is, 1. I've read where the idle screw is supposed to be backed out 1 1/2 turns. (I'm not sure where this is on the carb) 2. Is there a set way to adjust the throttle linkages? Or, what is proper way? I'm attaching a pic of the carb. Is the screw #30 supposed to not be turned in all the way? If so, problem may be solved as it is currently snug. Also, I don't have any compression readings yet, hopefully will soon though! Thanks for anyone's help on this!
Posted on Wednesday May 23, 2012 at 2:41 PM  
Thanks BJames.... I'm going to try and fool around with it some more... Like I said, I thought I had it running great (on muffs) until I put it in water, then it was a different story.
The carbs seem to open at the exact same time, I just can't figure out the rough idle. While idleing every once in awhile you have to push in the choke to keep it running (makes it idle high for about 10 seconds).

Also, I had put in 1 size hotter plug after coworker reccommended that. Going to try and go back to original though (try to rule that out).
Posted on Wednesday May 23, 2012 at 3:25 PM  
Running smooth with the muffs, and rough in the lake...sounds like maybe it's smooth when the motor is level and rough when not level....maybe a problem with the floats????
Posted on Thursday May 24, 2012 at 11:01 AM  
Yes... I went through 2 cans of cleaner actually!! Sprayed every orifice/passage I could see. Only line I didn't replace or put new clamps on was the line going to the fuel supply shut-off. I plan on going ahead and replacing it today.

This evening I'll try and tilt motor when on muffs (never thought of that) Thanks Slick!!

Just ordered the manual, I've been debating that, since there is so much info on net/forums but I figured what the heck.....

Thanks guys!
Posted on Tuesday May 29, 2012 at 12:00 PM  
As Bill said thirty is the cover screw over the idle jet - should be tight

On a two stroke cycle IF your reed valves aren't sealing on the compression stroke you will get a rough idle and poor performance at lower speeds - thats one possibility as well (they are internal and mounted on the backside of the plate your carbs are mounted on), and with an older motor its a good idea to eliminate this source - CCM makes some real good reeds these days--

You can get carb sync instructions online --

Screw 9 in all the way (snug not tight) and back off two turns MAKE sure the bleed hole is open and unobstructed, normally the more screwed in the higher your idle - after adjusting two turns out make third turn adjustments till motor idles at approximately 700 RPMs.
Those who would give up constitutional freedoms to elected officials in exchange for a false sense of security, deserve neither freedom or security.
Posted on Tuesday May 29, 2012 at 2:35 PM  
#9 is the idle orifice - and I should have looked at the year model - its fixed in 1984 - nothing to adjust EXCEPT idle linkage --

there are two needle jet orifices - low and high speed in that year model

MY Bad ---SO that said - you are back to

A- a partially clogged orifice
B- getting rubber/ plastic tank particles from Ethanol
C- reed valves worn or broken
D- bad compression

A compression check is in order -- do a leak down test, that will tell you if reeds are worn out
Those who would give up constitutional freedoms to elected officials in exchange for a false sense of security, deserve neither freedom or security.
Posted on Monday Aug 6, 2012 at 9:38 AM  
Lync and sync must be done correctly before any timing or idle can be set. Rough idle can be a reed issue air leak in hose crank case fuel pump so on or just carb being dirty. What's the compression. You may also run it in the dark on the hose and look for a spark leak. Or just use your finger if you're a man. Older omc s are bad about leaking spark.
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