custom fab'd pipes and performance

I have the stock headers but then the pipes open up and I have baffles. My intake is also custom, single K&N split to both carbs. Just tune to your setup... Though in some cases that's easier said than done...
hotrdd, your running a seven inch longer pipe on one side?
englishrose, the stock headpipes are double wall pipe to prevent blueing of the pipes. I don't think the after market makes a double wall pipe, cost to much to make. They use a single wall pipe.
On some bikes they use a heat sheild on the headpipes to cover the pipe to keep you from burning your leg and to hide the blueing.
XSLeo - I had the dino test done with those pipes and the single air intake. Do you think I should try and shorten the long side?
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If it runs ok and you like the look, run it that way. On a parallel twin most like the pipes the same length.
So I have the standard headers on my 76 that flare out to some 2” pipes that have 10” Vance and Hines quiet baffles inside. The exhaust is a little loud for my taste and I’m a little short on money right now so buying an expensive exhaust is out of the question. I do have a welder and time though. After pulling the baffles and do some more measuring it looks like some of the baffle wrap has slipped down a little but it might have happened when I pulled the baffles out, but I also discovered that the ID of the pipes was actually 2 1/8” not 2” that the baffles are. I also looked for external holes on the original headers to see if exhaust gas was leaking into the outside pipe but I didn’t find any holes and there doesn’t seem to be any leaking. SO I’m looking for some advice an which approach I should try and take to make it quieter.

1) Re-wrap the baffles and shim them to 2 1/8”?
2) Re-Wrap the baffles and shim them to 2 1/8” but also make the pipes longer and extend the baffles? (Lot of work but will put the rear of the pipes further behind me and give more room for baffle extension)
3) Cut the 2 1/8” pipes off and put 2” pipes on and then put the baffles back in?
4) Expand the pipe to 3” so that I can get more baffle insulation material around the baffles?
Your list of options and in that order sounds like what I might try. Start with the easiest thing first.
With the ID of your pipe at 2 1/8 and the baffle at 2. Then you will get some of the exhaust getting past the baffle with out flowimg through the baffle. The shim sounds like the best option.
If it helps then your going in the right direction.
So after driving around trying to find parts or more specifically NOT finding parts I have changed the plan. I haven’t completely taken a different direction but the plan has been modified slightly. I ended up at a Mom and Pop muffler shop and the owner was so intrigued by the experiment that he offered to help build me some new pipes and adjustable baffles for $50. We are going to re-create the baffles I have now but make them longer and so that they will fit some longer 24” 2 1/8” ID pipe. The baffles are going to have a smaller ID to match the XS and then the length will be adjustable so that I can tune them for the right sound. I’ll try to update as I progress later this week. This will also mean I need to play with the jetting again.
The pipes turned out great and sound great but as with almost everything else I would probably have changed them a bit if I did it again. I still haven’t been able to get the jetting right even though the pipes are now baffled and are the exact same length I’m getting surging in the 3500 – 5000 RPM range that makes going through corners scary. I’m going to try and pull my single K&N intake and put on two pod filters and see if that helps me with the jetting.

1) Since the P.O. cut up a lot of the bike the rear foot peg loops are missing and I’m having a hard time keeping the exhuast mounted to the bike. I’ve already rebuilt the bracket three times :mad:

2) The pipes sound perfect, not to loud but just loud enough that my BMW riding, Bluetooth helmet friends, have to stay back from me so that they can listen to the radio and make phone calls while we ride :thumbsup:

3) I built my own baffles that are about 18†long eith some perferated metal and a couple beers. They turned out awsome and I should have taken some pictures.

4) Once the baffles were packed and pushed into the exhaust I’m not sure that I will ever get them back out. It may be easier to build new pipes.
On your air intake, the K&N filter isn't ideal with cv carbs. With a two into one adapter so one filter feeds two carbs can only make it worse.
A filter with pleated elements and a taper or oval shape disrupts the air flow enough so the vaccumm in the carb is effected enough so the cv carb won't get the right slide lift. K&N makes a longer straight filter that is better.
I like the Uni Filter, it is straight with foam elements. Lots of good smooth air flow that cv carbs like and need.
I don't recall the item number but a four inch long filter with an intake diameter to match your carbs intake is what you need. I got the ones with a dual layer element. I think the extra element helps shed water.
Air straightens out and turbulence reduces the longer it runs down a tube so if you suspect a filter is causing too much turbulence it could be helpful to put a tube section between it and the carb. The usual setup where the carb is mounted straight to the intake port and a filter is stuck directly on the back of the carb amounts to a very short intake tract. I've been playing with a program called PipeMax lately that's used to calculate the best intake and exhaust lengths. Very interesting stuff. Seems the length and cross section of those can have just as much influence on the power band as a major cam change.
Another idea might be to rob the air straightener out of a junked MAF sensor? Less turbulence without increasing length.
GreasyC - who would have thought it would make such a difference? I think in my case I may be running into intake issue because one carb is closer to the filter than the other. I'll see if I can post some pictures later. Maybe you can put that into your program and see how I can build a dual carb intake that only has the one K&N air filter.
Yeah I was surprised to find out how much difference it can make too. Sounds like it's something where the effect becomes more powerfull the more you crank the throttle open, so if you're having this problem even at small throttle openings it's probably something else. I'm just starting to learn about it but here's a dramatic example I've seen. These are two dyno runs of the exact same engine with no changes except they put two different lengths of tube on the end of the throttle bodies. One is only 1.5 inches long, the other is 13 inches:


It basically changed the powerband from a revver into a tractor with just a simple swap. The guy said this was run at full throttle where the difference is the most noticeable and that the effect quickly disappeared at small throttle openings.

I found this information on a site called speedtalk where some big budget drag strip and circle track engine builders are talking shop. Check it out if you're into that kind of thing.

I'd be happy to put your numbers into pipemax but like I say I'm just learning and I have no idea how this works yet when more than one intake tube joins together. The only style I understand so far is a separate tube for each intake. They can all end up in a shared airbox with a single filter but each tube can be caluclated on it's own. This is actually how most stock motorcycle airboxes look. A row of little trumpets poking into a shared clean air box. Apparently the flared trumpet ends help airflow somehow.
Honestly I always assumed that mixing up the air and adding a little bit of turbulence would help with the fuel mixture / atomization. Maybe this weekend I can get a picture of my setup. What I’d really be interested in though is if someone has found an easy way to flow test their intakes at home? I don’t mind building something but not sure where to start. How can we measure how much “clean” air our carbs are getting?
Still not sure how to apply what you've got to pipemax. It seems to be more for calculating ideal runner sizes than simulating something that's already built. If you post some pictures of how you have the intake set up right now that might help but in the meantime here's the lengths it recommends for the xs:

- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 28.779 (usually this Length is never used)
2nd Harmonic= 16.334 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 11.403 (ProStock or Comp SheetMetal Intake)
4th Harmonic= 8.975 (Single-plane Intakes , less Torque)
5th Harmonic= 7.282 (Torque is reduced, even though Tuned Length)
6th Harmonic= 6.127 (Torque is reduced, even though Tuned Length)
7th Harmonic= 5.288 (Torque is greatly reduced, even though Tuned Length)
8th Harmonic= 4.651 (Torque is greatly reduced, even though Tuned Length)

Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood

It wants there to be a sudden change in pressure at the end of the calculated length, like a pipe suddenly ending in an air filter or airbox. Two pipes that length merging into one larger pipe at that point might count too but I think the merge pipe should be significantly larger than the individual runners to make that work. All lengths are in inches measured from the valve along the centerline of the port and intake tract. The program also recommends the diameter of the pipe to use but so far all the numbers I'm getting are way smaller than what's really used on the XS. I'm trying to find out why, will let you know if I do.
If it has one it usually looks like a grid or honeycomb just upstream from the sensor. There's also a blade type that has some flat vanes. Google MAF sensor and click images and you should get both styles. I don't know if these would help anyone but when car makers want to reduce turbulence so the sensor can get an accurate reading this is what they do.
I have seen a few factory air boxes with velocity stacks that extend inside the air cleaner, I assume to reduce dirty air flow at the jet.
Doesn't seem like it would be crazy hard to do the same thing with an aluminum velocity stack extending inside a Uni filter? I have always wondered why some sharp aftermarket air cleaner maker hasn't designed their spigots with a bell shaped inlet extending inside the filter?