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Cam follower adjustment for 1991 Johnson 25 HP (J25TELEI)

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Bevo2000

Member
I need help with adjusting the cam follower to sit between the two marks on the cam. Below is a picture of the instructions from the service manual. However, that procedure only allow the cam follower to touch the cam (or not). I can't move the cam follower back and forth to sit between the two marks if I follow the instructions. Am I missing something? This is the last adjustment I need to make before taking the boat to the lake for a test drive.

View attachment 24832
 
That cam roller does not sit there. That is the point where the carb starts opening. Set the roller so it touches just before the first mark. That way as the throttle advances the carb will open in the middle of those 2 marks.
 
flyingscott said:
That cam roller does not sit there. That is the point where the carb starts opening. Set the roller so it touches just before the first mark. That way as the throttle advances the carb will open in the middle of those 2 marks.
Click to expand...

Thank you Scott. My problem is I don't know how to move that roller back and forth. It seems like I can only adjust it up and down to touch the cam. Still trying to figure out how to move it bak and forth on the cam.
 
Bevo2000 said:
Thank you Scott. My problem is I don't know how to move that roller back and forth. It seems like I can only adjust it up and down to touch the cam. Still trying to figure out how to move it bak and forth on the cam.
Click to expand...
You dont move the roller. You move the cam itself with the throttle. Move the throttle until the cam marks line up with the roller. The roller can then be adjusted to start opening the carb. When you move the throttle back to slow the roller will not touch the cam at all. That is normal
 
If the set screw as per your service manual will not allow you to obtain that setting... I'd suspect that the following linkage (similar to yours) is somewhat out of adjustment. In which case, the following may be of use to you....................

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(Synchronization Of Older 2 Cyl Engines)
(Such As The 28, 33, 40hp Etc models )

On the linkage that runs from the armature plate (the plate the coils & points set on) to the carburetor throttle roller, loosen the set screw on the brass collar that you see there and temporarily move it away from the armature plate/vertical throttle arm clevis (clevis is that thing the linkage rod slides through). We'll refer to that vertical throttle arm/armature plate clevis simply as the "clevis" from this point on.

Look at the cam that's attached to the front of the armature plate.... the cam that slides up against the carburetor throttle roller. You'll notice that there's a scribe mark on it. Also notice that at the top portion of the intake manifold there is a raised portion, that top portion forming a point. The carburetor roller should contact the cam and just start to open the throttle butterfly when the scribe mark is dead center with that point.

With the engine in gear (not running of course) have the armature plate advanced all the way (by hand) so that it is up against its stop. Now adjust the brass collar (set screw) on that associated linkage rod so that it is up against the clevis. It should be adjusted so that there is either no play, or just a hairs play between the collar and the clevis.

At this point, the armature plate movement is not advancing the throttle butterfly via the rod movement, but further movement of the throttle control, although the armature plate cannot move any farther, causes the tension spring at the armature plate to allow the vertical throttle arm to move farther which now advances the carburetor throttle butterfly via the rod. When fully advanced (full throttle), the carburetor throttle butterfly should be fully opened (horizontal).

If all else with your engine is as it should be, that should do it.

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Thanks Scott and Joe. It's not perfect now but it's serviceable as is so I will try to do this adjustment later. It's time to take it to the lake for a test run :)
 
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