1984 70hp Johnson
The 1984 70hp carburetors have three (3) fixed fuel jets, the high speed jet is located in the bottom center of the float chamber, way in back of the drain screw, and should be marked 52D (ID= .054)
The slow speed jet is located, inserted directly in the top face area of the upper body and should be marked 42 (ID= .042)
The intermediate jet is located in the starboard top side of the upper body and should be marked 68 (ID= .068)
All jets must be perfectly clear & clean. The slow speed and intermediate speed jet are the same physical size and can accidentally be installed in the wrong location... check it!
The slow speed and the intermediate jet are both "fuel jets"... NOT... idle air bleed jets, and as such must have their screw in plugs screwed in place.
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Back the roller away from the cam to check the side throttle linkage. All throttle butterflies must open and close at the same time. You do not want one butterfly ever so slightly open when the others are closed. (sync) Now, adjust the throttle roller so that the butterflies just start to open when the scribe mark of the cam is dead center with the roller. (sync)
With the engine running and the scribe mark dead center with the roller, a timing light hooked to the top cylinder should show the idle timing mark (shown in your manual) on the flywheel. If not where it belongs, the distance between the vertical throttle arm and the metal cam is incorrect and must be corrected. (idle timing)
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The roller should be approximate 3/8" in diameter. If not, replace it
Let us know what you find.
