Fri Jan 29, 2010 9:48 am
My '47 A was running in a manner that was less than acceptable, so a while back I cleaned out the fuel tanks, lines and sediment bowl. This took care of most of the problem, but the old girl still loped some here and there under even a small load. Yesterday, I ventured out to do some work on our gravel driveway and she almost didn't start. When she did start, running was not the word. Almost sounded like only one or two cylinders were firing. I checked the spark on the coil and all of the plug wires... plenty of fire. Checked the firing order... correct. I opened the petcock on the carburetor... one drip every 5 seconds, maybe. I disconnected the fuel line from the carb and cracked the petcock on the bowl... plenty of flow. My guess is that the carb is gummed up and needs a rebuild. Am I on the right track? If this thing needs a rebuild, does anybody have instructions on the process of rebuild and adjustment? While I am semi-familiar with carburetors, this is not my area of expertise.
Fri Jan 29, 2010 10:18 am
Before doing a complete rebuild, check where fuel line enters carb. Most have a small filter or screen there that is probably plugged. if it is ok, there may be some trash in the opening for the float valve.
Fri Jan 29, 2010 10:19 am
Del, are you talking about a Cub
If so there is a screen at the inlet of the carburetor, this screen is most probably partially blocked. Remove the fuel line and look inside with a flashlight. If the screen is clear the carb will have to be removed and disassembled to check the float height and needle valve for obstruction.
Fri Jan 29, 2010 10:55 am
It certainly sounds like a fuel starvation issue. I have worked on a couple A's and a Super A and they do not differ that much I guess from a Cub. So the same diagnostics would apply. I have worked on a couple of Marvel Schleber carbs.. they are kinda fun
Does your A have the Marvel Schleber or the Zenith carb?
By looking at the parts breakdown in the TC-26E on the Marvel Schleber, Item # 50 is the filter screen. So I guess just take it apart carefully and see if there is crud somewhere between the fuel sediment bowl and the inlet. If not, then you will have to open the carb up. This does not indicate a full rebuild is necessary, but some TLC and ensuring the orifices and jets are clean as well as the needle and cage. On the Zenith it is Item # 25
Oh the server is down at the moment. The server is down so I emailed the Marvel and Zenith carb pages to you.
Fri Jan 29, 2010 12:28 pm
Thanks, Rudi! Apparently, I have the Marvel-Shebler model. Are you saying that I will have to tear into it to access that screen? If so, I assume I will need to replace the bowl to body gasket (#34). If I can access the screen from the point where the fuel line mates up, I may not have to worry about the gasket. I'll check it out shortly and let you know what I come up with. The email was VERY helpful!
Fri Jan 29, 2010 1:42 pm
I don't have a lot of experience with the Marvel Schleber, so I am going by memory which sometimes fails me. It appears that the filter is internal.. but you may be able to access from the exterior of the carb without taking it apart. I think that it might be a good idea to open the carb up though. All of the MS carbs I did needed cleaning as there was serious gunk/crub/varnish buildup inside. A can of carb cleaner will do wonders for that carb.
Glad I could help a bit. Enjoy playing with the A
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