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All,
After much searching I thought I would just ask... Have used this forum in the past to great success. Here is the issue:
C40TLRV, 1997 40 hp 3 cyl 2 stroke. Used more in winter. Started idling rough toward end of hunting season. Occasional misfire at idle. Sometimes but not always stalled in idle, only when in gear.
Didn't investigate that much on water. Brought it home to do annual maintenance. Put on muffs and miss became a little more regular. Stays running as long as I want it to and starts up no issue though. Temp sensor input for the warm up appears to be functioning normally. Started at the beginning of the periodic maintenance section in service manual to stay organized. I have:
1) Replaced fuel, checked lines, bulb, filter, pump, etc. Then ran some decarb.
2) Checked and ever so slightly adjusted throttle linkage (from control) and timing pointer following manual (probably could have left alone, adjusted 1 or 2 turns each).
3) Did the link and synch
4) Adjusted idle stop screw (although it is basically right back where it was)
5) Checked compression: 118, 121, 118 from top to bottom
6) Good spark on all 3 coils
All the adjustments etc above helped some and it is idling better. Misfire back to being only occasionally perceptible, but still doesn't sound quite right. Below are the specific issues that raise concern that I am seeing. I am thinking there might be more than one issue at play, and wanted to get the experts' advice about what to target and in what order to troubleshoot.
1) Top cylinder gets a little hotter than other two. I do not have a non contact thermometer but it is obvious. Not a huge difference, but obvious. Also, none of the plugs are too hot to touch after idling for 10 minutes or so.
What should op temp be?
2) There are pretty good amounts of oil in all 3 cylinders, and plugs 2 and 3 are wet after idle.
3) I suspect I will need to clean carbs and idle circuits may be clogged (WOT is fine on water), although this doesnt really explain wet plugs. Seems like opposite would be true. As a test I slowly closed each carb's pilot screw to document effects. None showed much effect much till I got pretty close to closed (1/2 to 1/4 turn out) Carb 1: motor stalled and died. This seems normal. Carb 2: seemed to actually run a slight bit better with screw seated. Carb 3: Right when I got to seated the engine slowed and acted as if it wanted to stall, but the effect was nowhere near as dramatic as Carb 1.
So, it seems maybe Carb 1 (or cyl 1) is carrying much of the load, Carb 2 (cyl 2) may actually be detrimental to idle, and number 3 is contributing some, but not much.
Question is: other than cleaning carbs with special attention to idle circuits, is there something else I should target. More specifically, does it sound like the poor running on cyl 2 and 3 come from a common issue, or am I looking for causes independent to each cylinder? It seems the effect of closing pilot screw on number 2 may indicate something with the prime start. Other than turning off and on manually is there a way to check the pump part other than disassembling? Valve part seems to be functioning correctly.
After much searching I thought I would just ask... Have used this forum in the past to great success. Here is the issue:
C40TLRV, 1997 40 hp 3 cyl 2 stroke. Used more in winter. Started idling rough toward end of hunting season. Occasional misfire at idle. Sometimes but not always stalled in idle, only when in gear.
Didn't investigate that much on water. Brought it home to do annual maintenance. Put on muffs and miss became a little more regular. Stays running as long as I want it to and starts up no issue though. Temp sensor input for the warm up appears to be functioning normally. Started at the beginning of the periodic maintenance section in service manual to stay organized. I have:
1) Replaced fuel, checked lines, bulb, filter, pump, etc. Then ran some decarb.
2) Checked and ever so slightly adjusted throttle linkage (from control) and timing pointer following manual (probably could have left alone, adjusted 1 or 2 turns each).
3) Did the link and synch
4) Adjusted idle stop screw (although it is basically right back where it was)
5) Checked compression: 118, 121, 118 from top to bottom
6) Good spark on all 3 coils
All the adjustments etc above helped some and it is idling better. Misfire back to being only occasionally perceptible, but still doesn't sound quite right. Below are the specific issues that raise concern that I am seeing. I am thinking there might be more than one issue at play, and wanted to get the experts' advice about what to target and in what order to troubleshoot.
1) Top cylinder gets a little hotter than other two. I do not have a non contact thermometer but it is obvious. Not a huge difference, but obvious. Also, none of the plugs are too hot to touch after idling for 10 minutes or so.
What should op temp be?
2) There are pretty good amounts of oil in all 3 cylinders, and plugs 2 and 3 are wet after idle.
3) I suspect I will need to clean carbs and idle circuits may be clogged (WOT is fine on water), although this doesnt really explain wet plugs. Seems like opposite would be true. As a test I slowly closed each carb's pilot screw to document effects. None showed much effect much till I got pretty close to closed (1/2 to 1/4 turn out) Carb 1: motor stalled and died. This seems normal. Carb 2: seemed to actually run a slight bit better with screw seated. Carb 3: Right when I got to seated the engine slowed and acted as if it wanted to stall, but the effect was nowhere near as dramatic as Carb 1.
So, it seems maybe Carb 1 (or cyl 1) is carrying much of the load, Carb 2 (cyl 2) may actually be detrimental to idle, and number 3 is contributing some, but not much.
Question is: other than cleaning carbs with special attention to idle circuits, is there something else I should target. More specifically, does it sound like the poor running on cyl 2 and 3 come from a common issue, or am I looking for causes independent to each cylinder? It seems the effect of closing pilot screw on number 2 may indicate something with the prime start. Other than turning off and on manually is there a way to check the pump part other than disassembling? Valve part seems to be functioning correctly.
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