Exhaust Scavenging

[Chadkid]

Hey Everyone,

I am rebuilding my old XS and purchasing aftermarket MAC pipes to replace the stock rusted set. My question is how noticable is the power increase from using a 4-1 system compared to the standard 4-2. I like the looks of the 4-2 but if there is noticable gain in acceleration with the 4-1 setup I'd rather go with that instead.

Any input would be great!

Thanks...
Chad B.

[John]

It has been said that the Mac headers aren't really all that good a header, but that's about all that's available for these bikes. I have a set on my 81 and I don't care for the sound of them, or the way the mufflers look. They also don't have a crossover pipe between then two sides like the stock pipes do. I would love to ge my hands on another set of Jardine spaghitti pipes though.
If you'd like to buy a decent used set of mac's, I have a set for sale. That'll save you a couple hundred bucks.

[Chadkid]

So the Jardine 4-1 setup will sound good?

http://jardine.rideshop.com/catalog/...roducts_id=633

They will out perform the 4-2 I assume...

[John]

I don't really know...I have never heard one.

[skids]

I have an older 4-1 that gets fantastic torque in the low end range. I have a newer one that isn't quite as good low range and I had to drill and rivot the baffle cone in place because it came loose. The headers look the same, but jetting is different.

Originally posted by Chadkid
So the Jardine 4-1 setup will sound good?

http://jardine.rideshop.com/catalog/...roducts_id=633

They will out perform the 4-2 I assume...

[skids]

PS. Exhaust scavenging is good only for a given range. This means that there could be some exhaust antiscavenging at other rpms.

[Chadkid]

Hmmm....


Would using a Jardine 4-1 pipe require rejetting?

I have a '79 Standard.

[chopwatchagot]

I have a Jardine 4 into 1 on my '80 standard. I like the sound of it and I think the power is there too, but this is my first XS and I have no experience with the stock units. I like the sound but it really is a bit loud after a couple of hours of highway speed driving.

[TADracer]

I have experienced the stock 4 into 2's, a set of Jardine 4 into 2' with the crossover pipe and now a set of MAC 4 into 1's, all on my 79 special.

The Jardines were a bit more free-flowing than the stock pipes and required about one jet size up from stock. They seemed to give slightly more torque but I did not notice much more than that. And, if you saw cut one section off of the baffle, they sound really nice. If you like a 4 into 2 arrangement, they are a good replacement for the stock pipes and the way the pipes cross over in front of the cylinder does look nice. But they did not have the slight upsweep on the muffler pipes like the specials have over the standards so that made the center stand hang slightly low. So, I just removed the thing and problem solved. When I need the center stand I just re-install it back....takes only a minute.

Now, the MAC 4 into 1's that I am running now made a difference you could readily feel. They required another jet size up and one on the pilot jet too. The power band does not come on until about 2,800 RPM but damn, you better be holding on after that. And it pulls smooth upto the redline without losing any steam at all. The big complaint I have about them is that the chrome seems sort of thin cause they blued up instantly when I started and I had already raised the jet sizes up. I do feel there must be better quality 4 into 1's available somewhere that will fit these bikes.

Hope this helps you out.

[TopCatGr58]

Hey Chad,

It's been so long since I put my 4-1 pipes on my previously stock 81SH that I can't really recall how it felt compared to stock?! But like Tad says, you can loose a little bit in the low end rpm range, but you gain it in the mid/upper rpm range. SO depending on where you like to run the engine, low and slow, or hot and high can reflect and influence which style of pipes you will want to go with.

With the 4-2 style you stand a better chance of keeping your low end torque, the Mac's don't cross over the cylinders like the Jardine do, so the exhaust pulses are not as well matched, which I believe also contributes to keeping some of the backpressure which aids the low rpm torque, vs. the more efficient scavenging of the Jardine, and even more of the 4-1 style.

My pipes were from JCW back when they used to sell them for the Xs11, and they were the Black Ceramic coated, so I wouldn't have to worry about the blueing!
T.C.

[Chadkid]

Thank you all for the info on this subject. I think Im going to go with the Jardine 4-1. My question is how does one determine the correct jet size adjustment given a change in exhaust configuration. Would I need a colortune plug? Or does the manufacturer provide the necessary info regarding this issue with their part?

[TADracer]

There is an article or tech tip somewhere here about jetting recommendations for various stages of modifications. Perhaps TC or one of the other mods knows right where it is. I used it with great results but that is a starting point. You will have to tweak your tune up for the best results.

I have a colortune kit but for me it seems to be a pain in the rear to use. Maybe I am just too old and set in my ways but I rely on reading the spark plugs. Most of your riding time will probably be spent in the mid-range where the engine is using both the pilot circuit and the needles. I ride for 15-20 minutes to let the spark plugs color up and then check the color of the plugs for the center insulators to be light tan. When too light or white you are lean and when dark and sooty you are too rich. You will know the sweet spot when you hit it. Also, if you look down into the plug with a magnifier you should see the color ring on the insulator indicating the flame front. If this ring is about half way up the insulator porcelain then you have the correct spark plug heat range.

Remember, a good tune up is a balancing act.

[mason79]

try this link

http://www.xs11.com/forum/showthread...=&threadid=382

[The Lorax]

I have the jardine 4-1 setup, I like it...I like the sound, I like the look, pretty much everything about it. I found them relatively easy to install, I did have to fab. a muffler mounting bracket for it but as far as install, that is my only complaint. I don't have my mixture fully dialed in as of yet, and the paint on the header did not hold up at all (I got the black, not chrome). but that is soon to be rectified as I am preparing to get some flat black header paint and will be baking that on in the not too distant future, I figure once that is done, I'll finish fooling around with the carbs and everything will be well with the world.

[Crazcnuk]

I picked up a set of S&S 4-2 headers. Anyone have any experience with these? They don't have the crossover.