1971 Johnson 20hp idle problems

[senate417]

Looking for some technical help for a 1971, 20 hp Johnson that will not idle
in or out of gear but operates fine at higher speeds. Fresh fuel and 50:1
mix and system has been cleaned and checked from the tank to the carb also.
Rich/lean needle valve adjustment does not help (currently 1 ? turns out)
even with linkage disconnected for more adjustment. I noticed a cam
follower and link and set screw attached to the throttle shaft which
actuates the throttle plate (butterfly) from a cam on the armature when the
grip is twisted. Is this how the idle is set? What is the correct rigging
procedure for this linkage? Should the grip be set to WOT (wide open
throttle) and the throttle plate be set accordingly.

 

[senate417]

Re: 1971 Johnson 20hp idle problems

edited may make more sense for the technical person

 

[tashasdaddy]

Re: 1971 Johnson 20hp idle problems

"Should the grip be set to WOT (wide open throttle) and the throttle plate be set accordingly." yes, there is a slide nut with a set screw on the rod just under the flywheel where the throttle linkage rod goes up the the flywheel, this is the adjustment. then you just do not turn throttle down too far.

 

[senate417]

Re: 1971 Johnson 20hp idle problems

is this the screw you are talking about? i do not see any slide nut assembly?

[img=http://img268.imageshack.us/img268/1631/dscn0106a.jpg]

 

[F_R]

Re: 1971 Johnson 20hp idle problems

is this the screw you are talking about? i do not see any slide nut assembly?

[img=http://img268.imageshack.us/img268/1631/dscn0106a.jpg]

1. Put shift in forward gear
2. Turn throttle grip to WOT
3. Carburetor butterfly should be wide open. If not, loosen the setscrew in your picture and adjust so that it is. Chances are it already is ok.
4. You aren't done yet. You have to synchronize the carb and spark, go on to #5
5. Retard throttle. You will see a mark on the cam that opens the carb. The carb shaft should just barely be ready to move when the roller (or whatever) is centered on that mark.
6. If it isn't right, there are two screws holding the cam to the armature plate. Loosen the one at the small end of the cam and move cam in or out as required to get correct opening time on the throttle shaft.

 

[senate417]

Re: 1971 Johnson 20hp idle problems

1. Put shift in forward gear
2. Turn throttle grip to WOT
3. Carburetor butterfly should be wide open. If not, loosen the setscrew in your picture and adjust so that it is. Chances are it already is ok.
4. You aren't done yet. You have to synchronize the carb and spark, go on to #5
5. Retard throttle. You will see a mark on the cam that opens the carb. The carb shaft should just barely be ready to move when the roller (or whatever) is centered on that mark.
6. If it isn't right, there are two screws holding the cam to the armature plate. Loosen the one at the small end of the cam and move cam in or out as required to get correct opening time on the throttle shaft.

thanks alot that was exactly what i was looking for. Going to try this then see how it goes and ill get back to you thanks alot!

 

[senate417]

Re: 1971 Johnson 20hp idle problems

tried moving cam but holes are not slotted so i cant move it..?

 

[F_R]

Re: 1971 Johnson 20hp idle problems

tried moving cam but holes are not slotted so i cant move it..?

Well, that at least is the way they've been set for a bunch of years. But they may have changed it. If so, the important thing is still when it opens in relation to the cam. Looks like you will have to move the arm & setscrew shown in your picture to accomplish the pick-up point and WOT will probably take care of itself.

 

[senate417]

Re: 1971 Johnson 20hp idle problems

only thing i can think of trying is replacing the spark plugs wut would you suggest for new ones? it currently champion j8c's

 

[senate417]

Re: 1971 Johnson 20hp idle problems

anyone?