Super A Gives a Loud Bang Through Muffler, Won't Start

Posted by SuperABen on March 04, 2013 at 17:52:11 from (99.197.193.128):

Excuse the long post, but its all necessary to explain the problem!

I'm stumped on my 1948 Super A. About a week ago, the Super A had been running for about 20 minutes. I had it pushing in a John Deere M (no comments, now) that I was rebuilding. I stopped to kick the block from under the Deere, while the Super A was running about 3/4 throttle, with a snow blade, so there was load on the Touch Control. I got back on the A, and gave it a little throttle to push the Deere. From the three seconds I had gotten off and back on the Farmall, it suddenly had no power. As in nearly stalling while moving in first gear down a slope. I cut it off and replaced the D21 plugs with fresh. It ran much better, well enough to push in the Deere (which was quite a load) and even scurry down the road in high gear. It was still sputtering slightly, but it had power.

I pulled the Farmall out a day ago to (once again) move a tractor. It started immediately, I am hand cranking, but it had no power, once again. It died while I was trying to ease it into an area where I could work on it. It wouldn't start back up.

I tried to yesterday, cold, and all I got after four hand cranks (choke at 1/2 like always) was one loud bang in the muffler/manifold. Enough to loosen the muffler from the exhaust pipe! No backfire, but just one loud bang. The engine didn't even try to start.

I have checked timing. Everything is in tip top shape: fires #1 right at TDC. It can jump a 1/4 air gap at the plug. All the valves are free and adjusted properly.

The carburetor is spotless: good fuel flow, no junk in the lines, clean jets. Before this happened, the tractor would idle low enough to count the fan blades. It is a Zenith with no high speed adjustments. Compression is good, equal within 5 +/- across all four cylinders.

I also have good clean fuel, I drained the tank and refilled. All I still get is a loud bang.

So the question is, what does the problem seem to be? I have worked on quite a few engines (but not as many as the folks on this list) but I've never heard such a bang without a hot engine and too much choke!

Thanks for your help!
Ben W.

Replies:

• Re: Super A Gives a Loud Bang Through Muffler, Won't Start rpsink 16:38:17 03/05/13 (0)
• Re: Super A Gives a Loud Bang Through Muffler, Won't Start Bill in IL 08:09:21 03/05/13 (0)
• Re: Super A Gives a Loud Bang Through Muffler, Won't Start Brownie 450 06:41:59 03/05/13 (0)
• Re: Super A Gives a Loud Bang Through Muffler, Won't Start mkirsch 05:14:42 03/05/13 (0)
• Re: Super A Gives a Loud Bang Through Muffler, Won't Start steve alderman 20:57:48 03/04/13 (0)
• Re: Super A Gives a Loud Bang Through Muffler, Won't Start Janicholson 19:33:34 03/04/13 (0)
• Re: Super A Gives a Loud Bang Through Muffler, Won't Start rpsink 18:06:59 03/04/13 (3)
  • Re: Super A Gives a Loud Bang Through Muffler, Won't Start SuperABen 18:15:09 03/04/13 (2)
    • Re: Super A Gives a Loud Bang Through Muffler, Won't Start Farmall Bob 03:59:21 03/05/13 (0)
    • Re: Super A Gives a Loud Bang Through Muffler, Won't Start teddy52food 19:04:18 03/04/13 (0)

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