The middle carb on my 2001 90 hp 3 cyl 2 cycle outboard motor is stickly/bumpy - it moves smoothly and easily for the first 1/2 or so of its travel range, then feels like its almost bumping into something, and takes a fair bit more force to overcome the stiction of whatever the problem is. The 2nd 1/2 of its travel is significantly stiffer, as well. The other 2 carb valves move easily and smoothly throughout their entire range of movement. (I disconnected the pushrod from the throttle arm of all 3, so that I could check them independently, and even hooked up the top and bottom, w/o the middle, and its still easy and smooth moving.)
The 'master' throttle arm (ie, that the throttle cable goes to from the control lever) pushes down on a roller attached to the middle carb throttle arm, and I was sure to keep that master arm up out of the way when testing the middle carb movement by itself. I also confirmed that the roller on the middle carb throttle arm does not have any flat spots, and that the underside of the master linkage that pushes down on the roller has no dirt, divots, etc - its all clean and smooth. There is also another pushrod running from the middle carb throttle arm to a valve of some sort further down inside the cowling (what is that little valve for??) - I disconnected that additional pushrod from the middle carb arm, as well, to ensure that it wasn't contributing to the problem. There's literally nothing on the outside of the carb that the arm is hitting on. The pushrod and little valve down in the bottom move super smooth and easy, as well, for what that's worth. I also found no play in the carb valve - it doesn't move side-to-side, up/down, etc - its a nice, snug fit - it just 'catches' part way through its range of motion, and is stiff in that 2nd half of its travel.
I didn't have any spray lube w/ me when this was discovered, to try to lube up the butterfly valve pivot where it sits in the carb body - that may end up resolving the problem, but I wanted to check here to see if this is perhaps a common problem, and what I might be able to do about it.
This is a problem for me because I have a throttle management system on my motor (for skiing), and its having problems due to the extra resistance being encountered at about the 1/2 way position on up. (Again, I've pretty definitively tracked this down to the middle carb - the other two carbs move smooth as butter, as does the unknown little valve down below (when disconnected from middle carb arm), as well as the pushrods and the 'master' throttle arm.) With *everything* disconnected from the middle carb arm, it still hits the 'bump', and then is stiff for the upper 1/2 of its travel range.
Thanks for any input/advice!
The 'master' throttle arm (ie, that the throttle cable goes to from the control lever) pushes down on a roller attached to the middle carb throttle arm, and I was sure to keep that master arm up out of the way when testing the middle carb movement by itself. I also confirmed that the roller on the middle carb throttle arm does not have any flat spots, and that the underside of the master linkage that pushes down on the roller has no dirt, divots, etc - its all clean and smooth. There is also another pushrod running from the middle carb throttle arm to a valve of some sort further down inside the cowling (what is that little valve for??) - I disconnected that additional pushrod from the middle carb arm, as well, to ensure that it wasn't contributing to the problem. There's literally nothing on the outside of the carb that the arm is hitting on. The pushrod and little valve down in the bottom move super smooth and easy, as well, for what that's worth. I also found no play in the carb valve - it doesn't move side-to-side, up/down, etc - its a nice, snug fit - it just 'catches' part way through its range of motion, and is stiff in that 2nd half of its travel.
I didn't have any spray lube w/ me when this was discovered, to try to lube up the butterfly valve pivot where it sits in the carb body - that may end up resolving the problem, but I wanted to check here to see if this is perhaps a common problem, and what I might be able to do about it.
This is a problem for me because I have a throttle management system on my motor (for skiing), and its having problems due to the extra resistance being encountered at about the 1/2 way position on up. (Again, I've pretty definitively tracked this down to the middle carb - the other two carbs move smooth as butter, as does the unknown little valve down below (when disconnected from middle carb arm), as well as the pushrods and the 'master' throttle arm.) With *everything* disconnected from the middle carb arm, it still hits the 'bump', and then is stiff for the upper 1/2 of its travel range.
Thanks for any input/advice!
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