Improving drag pipe performance

We had discussed this on another thread and I thought I'd bring it up again.
I recently removed the 10 1/2" baffles from my pipes and have been running them open since. After riding for a while, I have noticed a slight drop off in power at the top of the RPM range when shifting thru the lower gears.

So, I'm going to try the 3/4" washer trick. I already have screw holes near the end of the pipes so I figure I might as well make use of them. I fabricated all the pieces I need and just have to get the washers welded to the ends of the 1/4" bolts.

Dyno testing has shown an increase in HP/torque depending on how the washer is turned. More torque in the low to mid range if washer is set for most resistance (90 degrees to pipe) and moreHP if turned sideways.

Amazing to me that such a small thing can affect performance. Of coure, this is the "poor boy" solution to squeezing a bit more power out of the pipes but it appeals to my tinkering nature. Another benefit is that the sound difference is only very slightly affected - you still get the deep, open pipe sound, I've read. So, I guess a very little back pressure goes a long way.

Yup...No back pressure is the torque killer...

And I guess that torque is not an issue with my Indy Tattoo's bike (a lightweight bobber much like mine) because he upped the size of his '67 motor to over 100 c.i. He also has an S&S carb and home made drag pipes. His is a kick start, also. I've watched him start it and it's more of a push than a kick. He's got it dialed in so good that a "push" is enough to fire it up.

Very interesting . . . because I decided to try shortening my 10 1/2" baffles to 3 1/2" long. I put them back in yesterday and when I started it up, only a very small amount of sound was lost - the pipes still sound good.

I went for a test ride and noticed immediately that I had more power, so I think I'm going to stick with the shortened baffles. I know this is trial & error technology, if you can call it technology, but, hey, it worked. In fact, I have more torque than before - I can feel the motor pulling harder when I shift and on hills. I'm going to leave well enough alone.

Yeah, guys, a LITTLE back pressure goes a LONG way. Went for a longer ride today just to make sure I wasn't imagining things and sure enough - there's definitely more power than even when the baffles were 10 1/2" long. Guess I got lucky chopping about 2/3rds of the baffles off. Bike has never run better. When I bought the baffles from J&P, they were advertised as "making the 'man' happy", but nothing was said performance wise.

I rode to Tattoo's shop today and he said, "She sounds like a real motorcycle now".

Is that because it was a bad chrome job? I've had chromed items from the 50s (like headlight rims and bumpers) and they still looked really good.

I have read somewhere that the chroming process isn't what it used to be, because of the EPA & government interference . . . :cussing:

I've been doing more research on drag pipes and found that you only need enough back pressure to keep the reversion waves from re-entering the pipes and going back into the combustion chambers. A thing as simple as a 3/4" to a 7/8" washer (in a 1 1/2' exhaust pipe) will do this, or, as in my case, a shortened baffle will work, also.

Too much back pressure isn't good, either. Thanks, again, to the meddling EPA.

Now you got that silly song going thru my brain and it won't go away!

The Chordettes - Lollipop - YouTube :roflmao::roflmao: