Backfiring at top speed

Beast · Post by **Beast** » Fri May 18, 2012 10:10 am

My 53' a1 has developed a spudder and backfire at top speeds. If you hold it to 45mph or better for a distance it begins to load up and backfire. It cleans up if you push in the clutch and rev it up a few times. If you keep it under 40mph it runs fine. It also doesn't do it everytime either, kind of random. You'll be going along thinking it's fine and it will act up, and other times it will run without any problems at speed. It seams to me to be a fuel problem and I recently changed the fuel filter and that made no difference. Think it maybe the float level? Anyone have any ideas or had similar problems.

Post by **wesk** » Fri May 18, 2012 9:52 pm

You need to organize your troubleshooting. Eliminate the easy items first.

Check point gap, condition & timing.

Check fuel delivery pressure with a pressure gauge and fuel delivery volume with a clear container.

Inspect both vacuum diaphragms in the carb for condition.

Check float level.

Do a compression check.

Beast · Post by **Beast** » Tue May 22, 2012 1:21 pm

I had checked most of the basics. I pulled the plugs the other day and they were black and very sooty (running rich) After putting in new plugs it ran slightly better, mainly due to having clean plugs. So I'll dig into the vacuum diaphragms in the carb and after reading some stuff in the downloads section, also check the meetering rod. Hopefully I can get this thing running cleanly for it's first memorial parade here with the rest of the fleet.