johnhefley
Well-Known Member
- Joined
- Jun 16, 2011
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Last winter I was fortunate to procure from a very nice gentleman in Minnesota a C90 engine build kit with almost entirely new parts.
At the recommendation of my Cub Whisperer, I purchased a new Marvel Schebler carburetor for the build. He DID warn me early on that he ALWAYS has to return Marvel carbs, because the engine runs like crap with them installed “out of the box.”
He built up my C90, and we got it installed on my Cub. And it’s a BEAST on wheels and on floats with a Sensenich 39” pitch prop.
One problem: at most power settings (below WOT) the engine runs rough, and at a “reduced” RPM. Pulling the carburetor heat “on” smooths out the engine, and the RPM increases (obviously, the REVERSE of a properly set up carburetor). The initial install was accomplished with the mixture saftied in the full rich position due to lack of appropriate linkage hardware. Im operating below 1000’ above sea level for the most part.
It’s a 10-4252-2-F Marvel -Schebler Air MA-3SPA Carburetor for Continental C-90.
I’ve spoken with Wyatt at Marvel Schebler about this issue, and he’s happy to make adjustments. Based on what I told him (which is what I just stated, above), he thought a 1.5 gph increase in fuel flow should resolve the issue. My J3 has no electric system, much less an engine monitor, or EGT gauges. So rather than basing the modification by Marvel Schebler on data, I’m going entirely by “feel”, and “sound.”
I’m interested in hearing from others who have been down this path with Marvel Schebler carburetors, preferably someone who installed a Marvel Schebler on a C90.
At the recommendation of my Cub Whisperer, I purchased a new Marvel Schebler carburetor for the build. He DID warn me early on that he ALWAYS has to return Marvel carbs, because the engine runs like crap with them installed “out of the box.”
He built up my C90, and we got it installed on my Cub. And it’s a BEAST on wheels and on floats with a Sensenich 39” pitch prop.
One problem: at most power settings (below WOT) the engine runs rough, and at a “reduced” RPM. Pulling the carburetor heat “on” smooths out the engine, and the RPM increases (obviously, the REVERSE of a properly set up carburetor). The initial install was accomplished with the mixture saftied in the full rich position due to lack of appropriate linkage hardware. Im operating below 1000’ above sea level for the most part.
It’s a 10-4252-2-F Marvel -Schebler Air MA-3SPA Carburetor for Continental C-90.
I’ve spoken with Wyatt at Marvel Schebler about this issue, and he’s happy to make adjustments. Based on what I told him (which is what I just stated, above), he thought a 1.5 gph increase in fuel flow should resolve the issue. My J3 has no electric system, much less an engine monitor, or EGT gauges. So rather than basing the modification by Marvel Schebler on data, I’m going entirely by “feel”, and “sound.”
I’m interested in hearing from others who have been down this path with Marvel Schebler carburetors, preferably someone who installed a Marvel Schebler on a C90.
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