Johnson 10HP QD 19 carb question

[bob-d]

Motor starts and idles fine. When I go to accelerate it intially takes off bogs a bit, clears its throats then reaches full speed, at about 3/4 throttle.At full throttle it slows down a bit? New everything, points, plugs, wires, coils, and full rebuilt carb kit. Any ideas?
Thanks,
Bob D

[frankr]

Any chance the spark advance (armature plate) limiter it goofed up? Your description sounds like it is over-advancing.

[outbdnut2]

Yeah – what Frank said – and also be sure the throttle linkage isn’t pushing the butterfly in the carb past its full open position, starting to close it again.

The bog on acceleration from idle can sometimes be cured by turning the low speed carb knob slightly richer.
Dave

[bob-d]

Thanks Frank and Dave. Yep that’s it, the cam is falling off the armature plate at full throttle. Tried adjusting the amarture plate and was only able to get front to back movement, I was not able to move it to the left so that the cam would not fall off at the end of the travel. Is there a way to adjust the overall throttle movement, so that cam does not fall off. Looked around and was not able to find any additional adjustments to limited the cam.
Thanks,
Bob D

[frankr]

I’d rather think the armature plate itself is rotating too far. But not having it in front of me, can’t say.

[lloyd]

As I recall, There is another brass plate mounted under the magneto separate from the throttle advancing plate that has 2 notches in it that engage/hit the long shift arm on the right side of the block. First detent stops advance at shift position and second detent stops advance at WOT. Perhaps the plate is missing or maladjusted so that the arm is not engaging the detent at WOT and allowing the magneto to advance too far.

[bob-d]

Frank is there a way to limit the armature plate from rotating too far?
Thanks,
Bob D

[Mumbles]

You might want to check the condition of the notches on the brass stop plate which limits the amount of advance and throttle opening while in F-N-R. The vertical brass lever which engages the notches can get worn to or bent below the shift lever which won’t allow it to engage properly. Your stop plate should have three positions on it. One for starting while in neutral or warming up the motor, one for part throttle while in reverse, and the last one is for full throttle operation. It sounds like the third one isn’t catching and the mag plate is advancing too far.

• This reply was modified 4 years, 9 months ago by Mumbles.

[bob-d]

Jim, I think you figured it out. Thanks. Take a look at my shift arm, and the brass stop plate, both look pretty chewed up. Don’t let the paint job fool anyone. The old girl was pretty beat up when I got her 2 years ago.
If anyone has some serviceable replacements for a 58 10HP Johnson, PM me.
Everyone thanks again for suggestions on what was wrong.
Bob D

• This reply was modified 4 years, 9 months ago by Mumbles.

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