Well regardless, I've never seen a set of open pipes on the street that work as well as baffles. And the reason they glow has nothing to do with being lean - you are burning fuel in the pipe and that's what turns it dull red. Whether the carb is rich at idle, the choke is on, or the pressure wave traveling back up the pipe is interfering with normal gas propagation from the port, the end result is still the same.

If you are determined to run drags no matter what, and the bike ran fine before with mufflers on it, I would experiment with it by making the pipes longer or shorter to better fit your cam timing overlap, A/F ratio and ignition timing curve. During overlap when both the intake and exhaust valves are open at the same time you always get some unburned fuel that goes right out the open exhaust valve during cylinder scavenge. That is normal, but is usually kept to a minimum by the amount of back pressure that appears at the exhaust port after the pulse leaves the port. With open pipes where that pressure wave is undisturbed, you either have to break it up or change the point where it appears at the exhaust port by changing the length (or diameter) of the pipe.

Find some pieces of exhaust tubing that fit up the tailpipes and lengthen each one by 4-6" and try it. If that "fixes" it, then you have a choice - either order longer pipes or saw the ones you got off by the same amount you lengthened them with the temporary extensions. Either lengthening or shortening will change the resonance of the pipe, but will move that resonant point to another point on the rpm scale. Shorter pipes are better for high rpm, longer pipes better for lower rpm. With the wave propagation in the pipe being ~1125fps and about 12 pulses/sec at idle, if your pipe length is a harmonic of the fundamental resonant pulse frequency you will get the exact symptoms you describe. It's that simple.

Some people compensate for it by jetting up, which makes the charge less dense. A less dense charge has less mass flow, which limits the amount of unburned fuel that can escape during overlap. Jetting up is bad for fuel mileage and isn't going to do a damn thing for you at idle. You can recurve the ignition and advance timing (within limits) at the speed where you have the problem. Or you can change the cam to a profile and overlap timing event that is more suited to open pipes.

In the old days, fishtail tips were pretty common, if you can stand the sharp noise. You can install a set of expansion chambers that allow the pulse to expand and provide a high pressure restriction to a reverse pulse going back up the pipe. Constant diameter open tubes from port to tip are a bad design. Period. By far the easiest way to fix it is to just put a good set of performance mufflers on it, or buy a good set of baffled drag pipes.

 

Not to hijack, but HD...it has always been my understanding that pipes should be the same length, however many are not, what are your thoughts...???

 

They should be the same length for both jugs, but like you say many times they aren't. But drag pipes are mostly for show and I don't view them as being all that practical for the street. So in the end it doesn't make a lot of difference.

However, there are some well-designed drag pipes with baffles that work pretty good, and I think they actually have a better sound than open tubes and give the exhaust note a deeper tone. I had a set of baffled drag pipes on my XLCH with a 12.5:1 S&S engine in it, and they worked very well.

I've never seen the use of thumbscrews to make tuneable baffles like in one of the previous posts, but I've made them out of a stainless steel bolt with a 3/4" or 5/8" stainless steel washer TIG welded to it so the baffle is more in the center of the tube. I've built plenty of those for street rod engines where the owner insists on having to run zoomies to be super-cool. But with normally aspirated engines I've never gotten a set of zoomies, even with baffles, to match good headers with collectors on the dyno. Those open pipes will cost you 5-10% off the low and midrange torque every time. And even double wall chrome tubes will turn a dark blue to black a foot down the pipe after 15 minutes of run time. Some people consider that part of the "look". I consider it hard on exhaust valves.

 

You are quite right. Applies to drag pipes, but even more so to collectors, just look at any racing car with umpteen cylinders, or multi-cylinder bikes.

As I've said before, every production vehicle on the Planet with two or more cylinders, uses an exhaust system which unites all the cylinders into it's exhaust. There are jolly good reasons for that. Drag pipes are a just waste of useful tubing!

 

Sorry I wasn't clear, wasn't pertaining to drags, just exhaust in general. Like for example the two into one pipes . The front is clearly longer than the rear and say like a bagger exhaust with left and right side exhaust.
My drags are equal in length and would never run them without the cones.
Sorry for the confusion

 

The thumbscrew absolutely worked on my open fishtail pipes i used to run. Very noticeable difference with them. You can see it on the S&S dyno video and sheet I linked above as well.

This little demonstration shows how a well designed header with collector works to increase power.

 

By the way HBR, don't be this guy.

 

I don't care if it's a rice burner that is a god awful thing to do to any bike!!!!!!!!!!!

Too bad that dumb *** wasn't sitting on it when it went up!!!!!!!!!!!!

 

Totally agree.

 

Alcohol may have been involved......