Most of the choppers built tend to have some straight pipes. That simply means there is no longer any exhaustmanifold. That practice may have been founded in California back when customizing some old motorcycles began. That makes the bike sound very laud and the engine will pop when it is cranked up and the gas is quickly let of off.

The stock exhaust pipes always come with a manifold because it gives the engine some back pressure. It just doesn’t make as much noise.

Having straight pipes at sea level works fine. There is enough natural back pressure to let the engine run like it is supposed to. It’s just that the rider has to be cautious so the engine valves aren’t ever messed up. When you cut off an engine with straight pipes on any cold or rainy day some of that water and cold air can get sucked back into the engine heads and mess up the heads or valves.

Most of the bikers who are aware of this shut their bikes off with a lot of caution. They can get off of it and get a couple of rags. Then when the engine is shut off they can try to stuff the rags into the exhaust pipes right away. Some of them can get a friend or their old lady who they just gave a ride to for that shut down help.

Many of them just leave the grease rags in the pipes over night so none of the dust or water will get blown too far in. That rag up the exhaust pipes deal is used very carefully by all the riders of drag bikes. Their exhaust pipes tend to be a little larger than stock pipes.

Bikers who want their Sportster to sound more like a big twin could get them larger pipes themselves. They just had to watch out and make sure the pipes would clamp onto the engine heads. Many of the ones doing that cracked up when their chopper sounded more like a Shovel head anywhere around town.

One those bikers started riding in a higher elevation like New Mexico or Colorado they would find out those straight pipes would make the engine loose power as the climbed the mountains. The riders who could sense that tended to go to some custom cycle shops to find out if they could fix it without loosing the barking pipes.

With some luck they could find out that drag bike riders had come up with a tiny thing one just had to bolt inside the straight pipes. It was a round thing that had some fingers on it. The biker just had to remember to bend out some of those fingers to add the desired back pressure.

That combination of sound and back pressure became so popular in the nineties that chopper builders could start buying noisy exhaust pipes that looked just like the old straight ones and had something built in them for some back pressure. It’s just that them new exhaust pipes didn’t work in all the high elevations. And many city halls wouldn’t allow them bikers to make so much noise as they rode around town.

That’s why the only kind of exhaust pipes that could be bought in those places were just like stock ones. That turns out to make the old Harley engines run better and last longer. The riders don’t even have to worry about riding through some snow. It is also a good point that them old motorcycles tend to make a lot more noise than plain old cars and pickups. The rider can still laugh as he passes anyone in the rush hour traffic.

After learning these lessons my 1980 Sportster cracks me up while it is running fine.