My exhaust creation.

Thought I'd whack up a few picks of my endeavours.
I put an 33F motor in my 37H frame a while back and it has been good, but never quite as good as I wanted so...

I was given a complete 900 31A with a bad motor so I basically grabbed the wheels and swingarm and gave the rest away to other XJ'rs.

I also couldn't stand the way my 4into1 hit every single thing that was slightly raised including when I was doing some sweeping right hand turns and so... after doing some research and thinking all the crap exhausts were just as crap as each other I went on a bit of "I'll make it myself!" type of thing.

Also thought I'd put some of the sexy progressive springs into the forks and am now a definite supporter of the practice.. smooth braking for the win.. or FTW for the cool kids.

Pictures below.

I used 32mm Nominal Bore light wall Galvanised for the headers with 38mm mandrel bends for the 90degree into the head...
This is standard Australian CHS (circular hollow section) and the actual measurements are,
38mm ID
42.4mmOD
32mmNB bending form... funny stuff but the 38mm mandrel bends slip right in... very sexy!

I used 10mm cuts of the 32mm NB to make the stops on the headers and welded it all up with a MIG.

The plates/brackets I made out of some random pieces of plate that I welded together and ground the hell out of after drilling the holes.

The plate I used for the collector was some 1.8mm galv sheet that I had in the garage.

The pipe to the muffler is 63mm pipe from an exhaust place that I beat the end, into submission, until it matched my square fitting on the collector. I also put a slight bend in it first.

Did all the bends using a dawn bender (great piece of gear).

Enjoyed myself, as per usual... took it for a ride today and seemed good and I know I won't hit another speed hump with it as it is as high or higher than the original exhaust collector now.

Besides it will be damn hard to dent those headers on anything!

 

Very nice...Im sure you could sell your creation ...very creative.

 

Quite interesting. Bet it doesn't sound like your typical 4 into 1 exhaust.

Tony

 

No, it has a definite bark now, or a bark with a touch of a ring when its cold.
Next version will have some baffles to direct the flow a bit more I'm thinking.

 

Nice work but be careful when welding galvanized steel due to toxic fumes. Weld in a well ventilated area.

 

Bought a gas level mask a while back after a few spates of poisoning myself after welding... I swear I 'TRY' to remember to use it.
Once you jam the helmet on and start welding you really lose track of the amount of smoke in the area, not to mention in my garage when there isn't enough air flow to move the fumes out of the roller door and side door.
Next time I'll use that damn expensive mask... definitely!

 

That looks sharp, nice job!!

 

That looks absolutely amazing. I've been wanting to make my own sort of collector box. Its to bad I'm absolutely terrible with a welder

 

Grab som scrap and start laying down beads. Practice, practice, practice.

 

Hmmm...
Super lean!
Plugs are WHITE!

Time to pull off the exhaust and create some flow in the collector to try and simulate an extractor type situation... I think, maybe.

What do you reckon? Time for some artistic baffle creation?

Grinding is big part of the way I weld. BTW

 

Couldn't wait...
Time for surgery.
Open collector surgery!

Cut her open...

Open her up...

plan what to do... ish... and get some bits to make the baffles.

Cut and tack the baffles in...





Paint it with cold galvanising paint...

Close her up... with a big more colgalv... not as nice as the hightemp spray paint but beggars and all...

oh... and I used this, this time

 

Seems good...
after a colourtune I had to wind out the mix screws by 2/3 to 3/4 of a turn, to get a bit of orange so we shall see.
Sounds less barky thats for sure.

 

Hey mate, great work on your whole bike, not just the exhaust which I think is a great solution.
What suburb of Perth are you in? I would love to catch up and shoot the breeze and pick your brain sometime - I need some spark to get me going again on my project '84 750 and I would like to bounce some idas off you
Keep up the good work

 

Ideally you don't want any orange, just bunsen-blue; right about halfway betwen a touch of orange and a touch of white.

 

Shaynus, pm sent.

 

Happy to see you used the respirator so you can ride another day.

 

And replied to

 

Amaze-bums™! Rarely do we get to see a home brewed system that is as well thought out and executed as this. I would put that on my bike, for sure! And you were able to keep the center stand as well! Just excellent work.

 

Hi CDS,
Excellent work, what are the chances of a you tube sound check video?

 

John,
the sound is much nicer now with the baffles.
Tell you what I'll have a go at doing a video tomorrow and whack it up here.
I switched back to the a TCI from the erd dynapak and it runs a whole lot better too...
Strange! I will be investigating the regulator I'm thinking.
Get ready for tinny mobile phone audio! tomorrow

 

It doesn't really sound like this... or does it!
My ears don't hear all the ticky stuff in real life thats for sure.
http://xj.diagnostic.net.au/video/XJ900customexhaust.ogg

 

Looks pretty nice mate.....probably sounds better IRL than the mobile phone recording

 

Hi,
So...
I have a custom exhaust (https://www.xjbikes.com/forums/threads/my-exhaust-creation.106337/) and basically 31A (XJ900)configuration otherwise.

The temperature today was 28C and the bike was a beast.
The temperature yesterday was 39C and it popped and farted and ran like it was a piece of crap.

Okay, technically it ran like a piece of crap unless i slowly let it wind up instead of just accelerating.

So...
Question: I thinking just too lean all over and in the cooler weather I'm good?
Or do you think I need to look at my pilot jets? (which would suck of course)

Thanks!

 

Wouldn't the hot air make it richer?
Air less dense when hot, heavier when cold.

 

Very nice indeed!

 

Weaker if there was less oxygen perhaps?

 

Less oxy would make it rich...

 

Think about why we need to use the enricher on a cold day.
Colder air is denser (more molecules per cubic liter), causing the fuel mixture to lean out, so we compensate by dumping more fuel into the airstream until the engine warms up.

So if she's running fine in the warm and not in the hot, then you need to lean her out a bit. That farting and popping was unburnt fuel lighting-off inside of the exhaust.

Do a hot-weather run and see what the plugs look like.
What are you using for an air filter?
Just changing from the stock paper element to a reuseable foam element might be enough to get the mixture where it needs to be.

 

OK. I merged the two threads so we can all have the same look at the history of the exhaust and what the fueling arrangement was when you first installed it. Even though you linked the thread I'm not sure that anyone re-read it (Including me at first).
There are clues there. Just enough to start getting me confused.

You may in fact be too lean all over, but the engine should run fantastic in the hot weather if that's the case. I wonder if the collector box baffling isn't part of the problem. That long center plate may be interfering with scavenging, contributing to the poor running at high temperatures. I could also be entirely wrong about that.

One thing at a time though, especially since the exhaust takes the most amount of effort to change.

 

Can you make the mixture leaner in this situation by moving the clip on the tapered needle up a notch? Or is that needle kicking in further up the rev range?

 

I'm still thinking that she's rich at this point. The plugs will tell the tale though.

 

High humidity also = less oxygen therefore richer condition.
Cheers, 50gary

 

Makes sense! Fat air.
I will do some plug checks and let you know.
Thanks for the ideas/help.

 

Pics of my (they all look the same) plugs on a nice cool day 28 Degrees Celsius.
Hmmm... I like the look of them, what do you think?

 

Just did a google conversion on the temperature of the day that it was going nuts.
In Fahrenheit it was 102.2 and muggy (humid) as hell on the day.

Crazy the difference between then and now, but it was a few days ago.
I suppose the real question is what will the plugs look like after another day when it goes nuts...

Driving me nuts... that's for sure.

 

I welded it for 30 years every day building gates from galvanized pipe my boss said its not dangers to weld now have stage 4 lung cancer its from smoking all I hear welding galvanized in a enclosed shop had nothing to do with it.

 

Well, she's not running rich.

 

Liability-issues probably.
Metalvapors are VERY dangerous.
My college had 'weldinglungs' and that delivered some very weird mental situations.

 

Might not be anything, but here goes:

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......an inner tube (that carries that gas) and an outer tube that can stay relatively cooler and thus maintains its chromed 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 can physically be 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 gases 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 mighty important consideration.

http://www.gomog.com/allmorgan/exhaustbackpressure.html


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. 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 vent 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.

Or, maybe, aftermarket systems do no such thing:

http://www.motorcycleproject.com/text/exhausts2.html


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.

 

went in about 12 years ago said my iron was off the scale so was my zinc and chromium

 

Good info!
I do remember where I read about the pulsing and crossover, it was in your info pages!
When I did the baffles I specifically was thinking about the 1 to 2 and 3 to 4 cross flow and made them shorter while trying to separate the 2 until they hit the end pipe.
Not really 4 into 2 but a lot closer than the basic 4 into 1 that it replaced.
Hmmm, I wonder if the lack of heat dissipation on the headers might be playing a part also, since they are solid thick steel.

The main circuit is running fine, definitely in the idle circuit where I have the issue... more tuning required!

 

Damn, just re-read that... hmmm I definitely didn't make it that way... time for a redesign and some more surgery.

 

27C today, did a bunch of city riding and on the freeway, redlined it twice just to see.
Goes like a beast and the plugs are still the same, no fouling.
Hmmm... next summer maybe, before I can see the same symptoms. (well I wouldn't mind if that was the case, to be sure)
I will endeavour to reroute the collector baffles though, you never know.
Thanks again.

 

The design you have allows for too direct of flow, meaning you have no retained backpressure.. Your inner fins need reworked similar to the blue in this:
Here is a crude visual of what will help your design.

 

or just go with the Seca Turbo collector, centre stand would need to go though.

 

I Like it! a Lot.

 

Yes, in a perfect world but I'm deep in now!

 

You know that is impressive... fully isolated 2/3 from 1/4 till the turbo. Hmmm...
Like a riddle, in my current collector.

 

Hmmm,
This is the best Idea I could come up with based on the 2/3 being grouped together and 1/4 also, but isolated till the exhaust.
What do you think?

 

@cds1984 that should work.
Your welding looks great. Go for it!
One thing I would recommend you look at is the XJ mount for the OEM exhaust system.
It has rubber isolation but still supports a lot of weight. You could adapt it, It just stiffens the whole bike.