On 3/17/2015 6:20 AM, bob_villa wrote:
On Tuesday, March 17, 2015 at 7:11:55 AM UTC-5, TimR wrote:
When I was growing up car backfires were common. As a kid I had friends who could make it happen at will.

Now that the carburetor is long gone, most younger folk have never heard one. Fuel injection eliminated this, I think; could be wrong.

I never understood exactly what happens. Usually a car would backfire when under heavy load, and the gas suddenly let up. So my guess is the carburetor had a full charge with nowhere to go. But what ignited it?

Or, possibly the lack of air made an overly rich mixture escape the exhaust valves, and the explosion was in the manifold?

http://en.wikipedia.org/wiki/Back-fire


That article was pretty pedantic. What they refer to as backfire is more
popularly called 'carb farts' in the Harley world. Between a primitive
induction system, a wasted spark ignition, and EPA mandated leanness,
pre-FI bikes would tend to blow back through the carburetor. That could
be interesting if you were running without an air filter.

What the OP and most people refer to as a backfire is what the article
calls an afterfire. There were a couple of hills going into town. I'd
cut the ignition on my '51 Chevy and pull the choke as I rolled down in
gear to make sure people knew I was coming.