Exhaust question (again).

I've read a lot here about aftermarket exhaust but the jury still seems to be out on what effect if any it will have on the bikes performance and especially if there's a need to feck with the carbs or not.

Anyone put a MAC 4-2 replacement on and if so did you need to do anything to firstly get it to fit and/or need to do anything to the carbs?

 

Did a 650 seca with 4/1 Mac needed 116 main jets helped it pull hard all the way to 9000 and an extra 1/4 turn on pilot screws to idle nice. Altitude is always a factor, i'm at sea level so everything runs a bit lean stock, ends up just right at 2000 feet

 

So that's what I keep hearing - if you go 4-1 you need to re-jet but if you go 4-2 then you most likely don't. Has anyone used a 4-2 mac on an xj650 and got any experience they'd like to share?

This might be moot because I'm having a lot of trouble finding a 4-2 in black for the xj650 anyway.

 

Performance always trumps looks. Go with the chrome 4-2.

 

How does chrome effect performance?

 

? You implied that your choice was either a black 4-1 (color you want, but needs rejet), or chrome 4-2 (looks you don't want, but no rejet).

 

ah I see - nah I really want a 4-2 - I've seen them in black but having trouble finding one for xj650. I'm sure they're out there. If not I'll just bite the bullet and recondition the old one, wrap the pipes and sand/paint the muffs..

 

Changing the exhaust system by itself (leaving the intake side fully stock, including the pleated-paper style air filter) normally does not require re-jetting (unless, that is, you want to get rid of the "factory-lean" jetting that was used to satisfy EPA emissions regs of that time)......

 

This is easy.....If you can't find one in black, put the chrome set on and then ride only at night.

 

not completely sure but Mac 650's and 750's might be the same, could help your search. investigate further though.
personal opinion, Mac mufflers sound like poop

 

Thanks - are you talking about an after 10 pints and a curry poop or wine and steak poop?

 

Green apples

 

lol

So do y'all think this will fit on the xj650 maxim?

http://www.ebay.com/itm/Yamaha-XJ75...gaphone-Exhaust-System-204-1409-/161642612014

R>/

 

It'll fit as long as you have a couple muffler hangers with multiple holes so you can fit the hangers from the mufflers to the bolt holes for your muffler mounts on your foot peg brackets

 

if you look here, the 4/1 fits 650+750
http://www.motorhelmets.com/htm-bod...hones-complete-systems-yamaha-xj650-maxim.htm
but here the 4/2 only is listed for 650 with a separate listing for 750 seca
http://www.motorhelmets.com/htm-bod...to-2-complete-systems.htm?sort=newdesc&page=2
why...? center stand, side stand, mounts, hard to say
those from e-bay, are they one piece? separate pipes and mufflers would be better

 

Well, the 650 maxim doesn't have a collector box, just a single crossover pipe.

The 750 maxim has a collector box, so is a different mounting setup.

The 650 non-turbo seca has a collectorbox but is unique to that model.

The exhaust that Ribo asked about is a 4-into-2 with no collector box NOR crossover pipe, so it will fit pretty much any of them. The muffler hanger itself being the only thing to be aware of

Dave

 

so long as I can keep the center stand that would be good - thanks for the input.

What the benefit of having separate units rather than one piece?

 

EXHAUST SYSTEM OVERVIEW:

As with many other systems on these bikes, the Yamaha XJ-series of exhaust systems are a mini marvel-to-behold, well thought out and engineered......so please do keep this in mind when considering aftermarket "performance" exhaust systems.

Let's start with the headpipes: many of them are actually of a double-wall design......and inner tube (that carries that gas) and an outer tube that can stay relatively cooler and thus maintain its appearance much better and longer. Additionally, they are tuned in their internal (gas-carrying) pipe diameter to match the flow characteristics needed for their intended use.....thus, for example, even though the headpipes for an XJ650RJ Seca may physically installed onto an XJ700 engine, the inner pipe diameters do differ, and thus the swap may cause more harm than good, as it messes up with the balance of airflow thru the engine.

Pipe diameter helps determines (among other things) both the volume of exhaust gas that can be carried away, and, equally as important, the speed at which those gas will flow thru the pipe. All other things being equal, a bigger diameter pipe --- while surely capable of flowing more gas volume, will also slow down the progress of gas thru that pipe......which, in the world of exhaust gas flow --- and its important effects on intake gas flow (how well each cylinder can be scavenged of its burnt exhaust gases and allow for a full and complete incoming fuel/air charge) --- is a mightily important consideration.

By the way......although we've touched on some of the reasons above.....in regards to "swapping" headpipes between models, our best advice is: don't. Besides the whole "gas capacity and velocity" issues discussed above, there also the issue of fit: although the headpipes between a 550 and a 750 (for example) may look the same, and may actually bolt onto the cylinders heads, both their length and their unique bend angles ---- needed to follow the frame and mate up with the exhaust collector ---- will likely be different.


Next: the collector box. Although these weren't used on the XJ650 Maxim and XJ1100 models --- those bikes use a crossover pipe to perform the same function --- the collector box performs a few not-so-obvious but very important functions, and does it in a very admirable manner. First, of course, it provides a transition between the headpipes and the mufflers. Second, it keeps the decibel levels down to a reasonable volume. And finally....and very important for overall engine performance.....it provides a method of assisting that all-important "gas velocity" by providing a sufficient volume of space for "warehousing" (temporarily) the exhaust gas volume, while also providing (via its unique design) the ability to assist in providing maximal exhaust gas flow.

If you've ever looked carefully at your heavy (and probably-rusty) collector, you'll notice that it is designed ("split") in such a way so that cylinders 1 & 4 (the outer two) "share" a certain internal cavity space, while cylinders 2 & 3 "share" the rest of it. This is important because of the firing order of your engine: 1-2-4-3

If cylinders #1 and 2 --- which fire sequentially (and, thus need to exhaust their spent gases sequentially ---- were to share the same exhaust cavity, then their (sequential) exhaust gas flows would be "spaced" too close to each other (in time) and would see vastly different back-pressures (cylinder 2, which fires after cylinder 1, would see more back-pressure than cylinder 1, which emptied itself into a, well, into an "empty" exhaust collector).

To put it another way, cylinder #2 sees a lot more back-pressure than cylinder #1, because the gas pulse from #1 doesn't have much time to exit the system before the pulse from #2 is trying to squeeze itself in the same pipe. Notice that cylinders #3 and 4 have a similar situation.

The same thought goes for the other two cylinders (# 2 and 3). Notice how even the aftermarket "dual" exhaust systems suffer from the above problem, since they are really two separate system, one system being for cylinders #1 and 2 (left side) and the other being for #3 and 4. Notice how it's the "sequential" problem.....since cylinders 1 and 2 fire (and exhaust themselves) sequentially, and since those gases into one common chamber, that cylinder #2 is going to see more backpressure than cylinder #1 will......and same for #3 and 4.

This un-balanced situation....with different cylinders seeing different exhaust system back-pressures......can (and does) result in different amounts of burnt gas scavenging from the differing cylinders, which is not the way to get an engine to make the most amount of power.


Aftermarket 4-into-1 systems overcome this "differential scavenging" situation by re-introducing, somewhat, a "collector".......where the fours pipes come together into a common chamber, just before the muffler. This collector allows the system to maintain some amount of equalized back-pressure (and thus burnt gas scavenging), while the particular placement of the four headpipes, as they come into the collector, allows a little bit of "pull-thru" between each cylinder, helping to reduce overall system back-pressure levels, while still maintaining a somewhat equal amount of back-pressure to each cylinder.

Of course, the final piece of the puzzle is the mufflers, which are primarily decorative pieces....they look nice, stylish to the lines of the bike, contribute almost no back pressure to the system, and provide a nice throaty (but not too loud or droning or buzzing) sound output.


So just remember that the real heavy-lifting in the exhaust system is actually done by the headpipes and the unique, well-designed (but often overlooked) collector box.

 

..... And people wonder why I like to stay original------

 

Feck it - I'm just going to recondition the existing rig. Can you tell me how it's put together - i.e. when I take it of will it come off in pieces that can be easily put back together?

Is it easy to swap out the mufflers for a nice set of aftermarket ones? Are there different sizes etc etc?

 

The 650maxim: 4 separate exhaust pipes, two collector/muffler units.

Loosen both muffler mounts, the crossover pipe slip joint, the four exhaust bottom clamps, the eight exhaust collar bolts.
Take thing apart in whatever order works best for you.

Personally, to REMOVE an exhaust, I just remove the collar nuts, then the muffler mounting bolts. Then slide/wiggle the whe system forward til the collars slide off the studs. Then lower othe whole system to the ground. Turn the front wheel and you can rotate the whole assembly and slide it out from under the bike.

Two questions: What condition are the parts in? What are you going to do with them? I may be interested--- I'll send a conversation.

 

Maybe this will help..., here's a pic of the right-hand side. You can see the two receivers at the top for the exhaust pipes, and part way down you can see the section of crossover pipe. Then below that, you can see where the muffler is factory welded on. That's why it's a single-piece muffler/collector.

 

Cool thanks man. I didn't realize that was one piece.

 

I figured that you weren't getting that part, so a pic is worth a thousand words

Dave