Karmy Flying Adventures Rockn the left coast at 100ft

March 31, 2009

Fixing the alternate air door

Filed under: Firewall Forward,Maintenance — Andy @ 1:20 pm

airdoor1In doing my annual this year I found that the carb air door hinge was starting to fail. Wear from vibration over the years had eaten away at the hinge eyelets to the point where in the next year it was clear it might fail. So time for a quick order to Vans for a section of new hinge. In spite of the fact that this hinge is the extruded (stronger) type, the brass pin in the center of the hinge proved to be a good cutter with some vibration added to the mix.

For the repair, I drilled a hole on each side of the hinge, so now I can simply push out the center pin when I need to remove the door for service. Then drill out the hinge rivets, match drill up a new section of hinge and re-install the pin and we’re good to go. I just capped the new holes with a dab of RTV to keep the pin in place if it decides to walk over time.


March 16, 2009

Carb Float Replacement

Filed under: Firewall Forward,Maintenance — Andy @ 12:59 pm

This year at Annual time I found a new AD that required the replacement of the float in my Marvel Schraber  MA4-SPA carb. All of the details can be found on the Volare site (owner of the precision carb line). Suffice it to say that there have been problems with floats over the years and they want to get all of the white plastic floats out of the field to ensure the safety of engine operation. I had my friend Marv (our local EAA tech counselor) come help give some advice while doing the project which made it go smoothly! I ordered the float kit from A.E.R.O. in Granite City, Illinois

carb1First up was to open up the carb. We think of these things as the precision instruments that they are, and yes a hammer is required to get the bowl separated! Yikes. It’s just 4 screws that you pull and then crack the gasket seal to open it up. Inside I found the dreaded white plastic float. Guess it was a good call to do the work and replace it as these have had some problems over the years. When you look at it closely, there is no question that it could have problems.

The old float easily came out and the new blue float was a perfect fit to go in its place. The main section of work was to align very carefully the float level of the new float. Now as it turns out my old float was not that well aligned, with one side higher than the other so we could only make it better in the process. The instructions called for using a 7/32″ drill bit as a feeler gauge between the gasket and the top of the float. This worked fine and after a few on and off small bends and twists, both sides were setup per the instructions and moved freely throughout the range of travel.

Now all you do is use a new gasket and put the two halves back together, tighten down the 4 screws, let it sit a bit to compress the cork gasket, then do a final tighten and bend the lock tabs in place. Mark the data plate on the front of the carb to indicate that you replaced the float (to help out the next guy) and update your logs.

The engine ran fine after the replacement, with a slight idle mixture change of half a turn leaner it was running good. YEA!

Here are the links to some reference material on the subject


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