Anybody ever have a binding butterfly on a marvel ma-4spa carb? I've been battling a problem with what now appears to be my carb. I was noticing high forces on my throttle cable after flying for a hour or so. At first I thought i was being stupid and not releasing the knurled knob enough.
About a month ago on downwind the throttle was essentially locked up at a partial power setting. I was able to land safely and decided that the cable was defective. I bought another throttle cable and installed it.
Today the same thing. I was able to land again safely and quickly removed the cowling and disconnected the cable from the butterfly level and sure enough, the butterfly would only move if subjected to high forces and a screaching sound was emitted. Kind of like when you loosen a rusted nut. 15 minutes later the butterfly was moving freely like nothing happened.
As this point a assume that the clearance between the shaft O.D. and bushing/hole I.D. is too tight and when the carb expands due to engine heating the shaft binds up.
This is a rebuilt carb from airmotive which was included in a new engine from aerosport. the whole setup has less than 30 hrs on it. I plan a calling Bart tomorrow but has anyone heard of such a thing before? This is scary situation and it would seem to me that a newly rebuilt carb with paperwork wouldn't have these problems. I plan on putting the carb in the oven tonight @200f when my wife isn't looking and see if i can duplicate it.
Frustrating since the weather here in Philly finally looks good for the next couple of days and I'm grounded again.
It's always something.
Doug Meloche
About a month ago on downwind the throttle was essentially locked up at a partial power setting. I was able to land safely and decided that the cable was defective. I bought another throttle cable and installed it.
Today the same thing. I was able to land again safely and quickly removed the cowling and disconnected the cable from the butterfly level and sure enough, the butterfly would only move if subjected to high forces and a screaching sound was emitted. Kind of like when you loosen a rusted nut. 15 minutes later the butterfly was moving freely like nothing happened.
As this point a assume that the clearance between the shaft O.D. and bushing/hole I.D. is too tight and when the carb expands due to engine heating the shaft binds up.
This is a rebuilt carb from airmotive which was included in a new engine from aerosport. the whole setup has less than 30 hrs on it. I plan a calling Bart tomorrow but has anyone heard of such a thing before? This is scary situation and it would seem to me that a newly rebuilt carb with paperwork wouldn't have these problems. I plan on putting the carb in the oven tonight @200f when my wife isn't looking and see if i can duplicate it.
Frustrating since the weather here in Philly finally looks good for the next couple of days and I'm grounded again.
It's always something.
Doug Meloche