Marvel Schebler MA-3SPA problems

C

citabrick

New member
Hello,
Recently the carb on my 1964 Citabria with an O-200A had a fuel leak. I sent the carb to a shop and had it repaired. While at the shop a one piece venturi and an atomizer style fuel nozzle were installed. Now my engine is not making full power and runs very rich. On a ground run, if I go full throttle the engine runs very rough and emits black smoke, if I throttle back to 3/4 throttle the RPM goes up and it runs smoother. I have sent the carb back to the shop and they even ran it on a test cell engine and can find no fault. Has anyone here had this problem? If so what was the cure?
 
Check to make sure your not leaking any carb heat first. Your box may need attention. Have you tried pulling your mixture out a bit and see what happens. Was the test engine at the same elevation as you? Did they pull the mixture back or leave it full rich?
 
Thanks for the reply. I did lean it out and then it runs better. I'm going to have a closer look at the box next, but I think it's alright. I think the elevation of the shop is about 700ft asl and I'm at about 800ft asl. As it is now with the mixture full rich I can only get about 2450 RPM and with it leaned out I get about 2600 RPM. The only way I get close to this RPM (2550)at full rich is to throttle back a little. I must say it is rather frustrating.
 
Before I bought the Champ I have, with an O-235 in it, the owner was making sure all ADs and the annual was done on it. Well, there was an AD on the carb that required the placement of the one-piece ventury to be installed. He had the same problem....could not get full power. He found out that the AD was rescended and replaced the one-piece back to the two piece and ironically the power returned. I also read that some of those venturies had roughness in them and they needed to be polished out. But double check that before believing anything I say.
Good Luck.

Keith
 
Check your mag timing, make sure your not getting carb heat, be certain your primer is in and locked, even better you might want to disconnect it and cap the line just to be sure you are not drawing fuel through the primer. Then if you have compression and fire it should run correctly if it is getting fuel in the right porportion. The cause then of a rich mixture would be the carb.


Woodie
 
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