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howie123 · 05-12-2014, 05:11 PM

When driving my Model A speedster it starts easily and runs well. At about 30 mph I start to get a spitting or light popping noise from the exhaust. It blows black soot out the tailpipe and the spark plugs have a light coating of soft black soot. Fuel mileage is also quite poor. I am running a fuel pump and regulator. I checked the pressure at 1 psi. I replaced the Zenith carburetor with a Marvel. It still runs fine but the same symptoms persist. I am using W18 spark plugs. Tried some W14 that I had just for fun with no change. I also tried a different condensor with no change. I have double and triple checked the timing. The last time I checked the spark looked strong. I am running out of ideas. Any help would be appreciated. Thanks. Howie.

05-12-2014, 05:11 PM	#1
howie123 Senior Member Join Date: Jul 2010 Location: Eau Claire, WI Posts: 113	Need help with persistent problem. When driving my Model A speedster it starts easily and runs well. At about 30 mph I start to get a spitting or light popping noise from the exhaust. It blows black soot out the tailpipe and the spark plugs have a light coating of soft black soot. Fuel mileage is also quite poor. I am running a fuel pump and regulator. I checked the pressure at 1 psi. I replaced the Zenith carburetor with a Marvel. It still runs fine but the same symptoms persist. I am using W18 spark plugs. Tried some W14 that I had just for fun with no change. I also tried a different condensor with no change. I have double and triple checked the timing. The last time I checked the spark looked strong. I am running out of ideas. Any help would be appreciated. Thanks. Howie.