shortstripper
15th May 2005, 15:36
Hi,
I wonder if anybody has any ideas on a problem I'm having with a C90?
I had to make a quick landing the other day as she started to run very rough at the top of the climb. I put it dow to carb ice as I had no time that day to investigate further. Having warned the group, another member went to fly today and despite a perfectly ok run up and power check, she started to play up just as he was getting airborne, so he aborted.
Now, I'm sure it's not a sticky valve as I had one recently which I sorted and this is nothing like that. I guess it's possible, but I'm pretty sure it's not. The timing is OK and anyway the engine doesn't miss a beat throughout the rev range under no load. This then brings us to carberation, which is always a bit of a black science unless you have test equipment. She was running a bit rich a while back, but after adjustment (a little each flight until all seemed right and the sooty exhaust pipes cleaned up) she has been running fine for the last 20 hours or so.
So to sum up ...
Runs throughout the rev range perfectly ok on the ground during power checks, timing seems ok, mixture "seems" to be about right, but .... at full power once flying she starts to miss and run rough!
I did wonder about fuel supply? could the fuel pump be getting weak? or the carb float (if it has one? "marvel carb") be fuel logged? This might show itself as demand for fuel increases under high power conditions?
Any ideas? I have a reasonable mechanical experience, but I'm certainly no expert and I'd appreciate the thoughts of those who are. :\
Thanks ... SS
I wonder if anybody has any ideas on a problem I'm having with a C90?
I had to make a quick landing the other day as she started to run very rough at the top of the climb. I put it dow to carb ice as I had no time that day to investigate further. Having warned the group, another member went to fly today and despite a perfectly ok run up and power check, she started to play up just as he was getting airborne, so he aborted.
Now, I'm sure it's not a sticky valve as I had one recently which I sorted and this is nothing like that. I guess it's possible, but I'm pretty sure it's not. The timing is OK and anyway the engine doesn't miss a beat throughout the rev range under no load. This then brings us to carberation, which is always a bit of a black science unless you have test equipment. She was running a bit rich a while back, but after adjustment (a little each flight until all seemed right and the sooty exhaust pipes cleaned up) she has been running fine for the last 20 hours or so.
So to sum up ...
Runs throughout the rev range perfectly ok on the ground during power checks, timing seems ok, mixture "seems" to be about right, but .... at full power once flying she starts to miss and run rough!
I did wonder about fuel supply? could the fuel pump be getting weak? or the carb float (if it has one? "marvel carb") be fuel logged? This might show itself as demand for fuel increases under high power conditions?
Any ideas? I have a reasonable mechanical experience, but I'm certainly no expert and I'd appreciate the thoughts of those who are. :\
Thanks ... SS