Topic: drag pipes and backpressure

[Mach5]

Ok, drag pipes came with my bike. I would really like the 4 into 1 setup, but cost keeps me from going that route. Has anyone modified drag pipes to increase backpressure? Maybe put a plug in or a crossover?

[HondaMan]

There used to be a device called the "Snuff-R-Not", which was essentially a washer mounted on a springloaded post with an outside-of-the-pipe knob on it. You drilled a little hole in the side of the pipe, assembled this big washer across the open pipe and connected its shaft to the knob and spring, so you could open or close the pipe with a 90-degree knob twist. The backpressure worked well on the short open headers, smoothing out (and cooling off) the engine. Choppers seemed to always use them, don't know it they are still around. They were first intended for small-displacement single-cylinder dirt bikes (early 1960s stuff).

[CountRockula]

If you ever want to sell them let me know.  I'm desperately looking for a set.

[GNXFan]

Those Snuff or Nots were big  in the 60's on CL77 305 Scramblers. Guys would cut off the muffler at the end of the pipes and run straight pipes with the Snuffs.Here is a place that sells Snuffs but their not exactly like Hondaman described.

[HondaMan]

Those Snuff or Nots were big  in the 60's on CL77 305 Scramblers. Guys would cut off the muffler at the end of the pipes and run straight pipes with the Snuffs.Here is a place that sells Snuffs but their not exactly like Hondaman described.

Those look like a 2008 rendition of the old ones! They should work fine today, like they did then. They increase the midrange backpressure enough to reduce the flat spots, but you will find that you need a little more jet up high. One way to fix it: increase mainjet by 5, then watch the plugs. If it gets too rich in the midrange where you ride, drop back on the mainjet, think about raising the needles a notch. If that gets it closer and the top end doesn't lean out, drop the main another 5 size. This all depends on the length of those pipes, and whether they have squared or round bends. Both were popular back then.

These types of baffles do not introduce a smooth flow, but rather a peaky spot of good flow that slows suddenly at resonant RPM. This RPM depends on the cam being used: running it late will extend the RPM range while the increased midrange of the straight pipes will lift up that flat feeling at 4-5K RPM. It just so happens that the increased midrange was exactly what the old 305 Scrambler needed, and these were just the ticket. They worked just as well on the 160 twin, which had the same volumetric efficiency, but with 180 timing. Neither of those bikes had much top RPM, anyway.

[fuzzybutt]

there are baffles sold to fit into the mac drag pipes too. cyclex has em