Muffler Baffling, Why?

I am new to the mototcycle world. I am looking into customising my pipes. I like the straight pipe look and sound. Here is the question. Why is baffling needed for your pipes? What damage could be caused by not using baffling in your pipes? Thanks for any help I am trying to learn as much as I can before I make any changes to prevent doing something stupid.

 

First off , it keeps the heat off your back , and cash in your wallet.

"heat" meaning "cops"- - Five-Oh- - "The Garda"

Second, there is no actual horsepower gain on an XJ by gutting the exhaust.
With straight pipes and no baffles you will sound like a rippin' race car ALL the TIME !! It gets annoying, but based on what I've read from this site, you won't actually damage your motor, assuming you've checked your valve lash, run a decent oil, have your carbs sorted, ETC.

You also won't be able to hear problems as they pop up.

 

Plus pissing off your neighbors, everyone driving behind you or beside you, pedestrians, and ESPECIALLY law enforcement.

"If loud pipes save lives, imagine what learning to ride that thing will do!"

 

I don't know, I think there is something to be said for exhaust scaveging and back pressure.

I know that a car will run like crap if there is NOT enough back pressure.

And the engineers go to great lengths to design around the benefit of exhaust scaveging.

 

No exhaust equals pissed neighbours, and no back pressure equals reduced performance and possible burned valves. As Skippy344 stated, the engineers designed it to run that way for a reason. Power loss may be minimal and not very noticeable when you are talking about a 75 horse motor vs a 300+ horse motot, but it is there.

Just my .02 worth..

 

WOW, okay aside from the obvious noise factor. What "mechanical" issues can arise from not having any baffling? I have been hearing talk about a lack of back pressure causing the engine to run hotter than normal. This could abviously cause damage after prolonged use.

Is this a true statement or just talk?

 

To clarify- - there's two levels of going "straight pipe."
One is to remove the mufflers, and fit some pipes to the collector.
This still leaves some muffling, baffling, and back pressure.
It's still loud, but with long, skinny pipes, would be tolerable.

The second level is where you lop off the last 2 inches of the header pipes and have 4 screaming ends under your feet. The engine scavenges so much it runs lean, which makes it run hotter, and you are wasting a bit of fuel straight out the pipes. The engine was not designed to run like this, but the few here that have have not complained of burned valves.

I prefer quiet and fast !!

 

When you compare the number of kilometers (for those of us North of the 49th) ridden by cagers, which is estimated at an average of 25,000 KM per year, and compare that to the number of KM an average rider will put on (mine is an 85 with just over 54,000 KM), then it will take much longer to happen. But as we all know, running lean with the XJ's is asking for trouble down the road, and I personally wouldn't make any mods that would add to it running leaner. If it were a newer bike that was injected, and could adjust it's mixture, I wouldn't think twice, but that's not the case.
Heck, it's hard enough keeping the mixture correct when everything is running like it should, and stock. Of course, you could cook other parts as well.

"exert"
Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition.

 

I have a question on that, then. I have an xj550 maxim. I know its next to the baby of xj models, but its quick as hell and I am just attached to it. More than any bike I've ever had

Well, anyway... I just modded the carbs with K&N pods and rejetted to suit... actually a little more than needed. Went from 1.12 mains to 1.25.

The performance boost just from that is beyond what I expected but now I have to run it on PRI (prime) instead of "run". (referring to settings on the petcock) The vacuum system doesnt pull enough fuel in, otherwise. I am turning this into a rat bobber and I know I am way off in tradition here, but I am installing the Mac 4 into 1 exhaust instead of straights or baffled tips, etc. Hoping this will balance things out.
With this set up, what would you suggest if its different than what I am doing.

 

Where did you come up with this theory? There are so many false statements in the post above that I cant even begin to list them all. I have heard a bunch of bs in my day but I'd have to say this takes the cake.

What you are basically saying is that after the air gets mixed with fuel on the outlet side of the carb the back pressure caused by the exhaust forces it back through the carb and into it once again.

-Please do not believe everything you read on the internet. Anyone with even basic knowledge of how an engine operates will know how untrue this is.

 

Well, if you're going to run without baffles, make sure you don't park it outside......

 

very interesting posts.
i hated the stock sound on my 700n.
i drilled off the rivits on the exhaust back plates, re-drilled those same
5 rivit holes with a 3/4" bit.
let a riding buddy do a few passes so i could hear how they sound.
AWESOME if you like a crotch rocket.
sounds like a much "meatier" motor.
and of course does not at all match the cruiser look even a little.
only a slight change for the better in smoothness and performance.
i'm leaning towards screaming eagles or hard chrome straights with
fish tail caps.
as for the loss of back pressure and its affect on the motor.......i'm learning
this like the rest of you....as i go.

 

I used to fill my roomies pipe on his Harley with dog poo. From his dog.

To the gent double charging his mixture, check the intake valve. It's either setting or sealing that's making it do that.

 

Now THAT - is one pissed off neighbor! Good luck getting that stuff off....

 

I plan on going to a long straigt pipe. Most likely a 4 into 2, but I don't know maybe have a 4 piper. As to the baffling, I am most likely going to use some minor baffling since I don't even want to run the risk of burning this bad-boy up.

THANK for all the good info

 

Altus, you are a wise and considerate person and I applaud your common sense! Why does LEO continually ignore those POS V-Twin riders (i don't just mean Harley's here) and let them get away with that RIDICULOUS amount of noise??? How many feel that they could cut the exhaust off their 4 wheeled rides just before the cat and get away with it? It's absurd. The cacophony created by these idiots gives the rest of us a bad name.

If you want deeper, reasonably louder exhaust there must be a way to do it. Don't cut the pipes at the header and piss off the world while giving M/C's and their riders a bad name.

Rant over. You are now being returned to your regular thread.......

 

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i played with my exhaust on my 700 and made im own 4 into 2 and didn't care for the sound of it. after doing some researching, i found that a 4 into 1 is the way to go, both for sound quality and looks. first i was running just the header pipe,(way to loud) then the tail piece without the baffle(even louder) so i cut the baffle in half and thats how im running now. sounds good and not over the top loud, plus the added back pressure makes for better throttle response...

 

1FASTHOE, what type of "tail piece".
was it homemade or did you cut off a store bought muffler( kerker, mac, v&h etc)?
i'm just curious since i have'nt desided how to go yet.

what i whould like is a deep rumble, not a loud noisy scream.
although i'm most likely just dreaming with this little 700.

any thouhgts would be great.

thx.ron

 

the mac system comes in two pieces, the header and the muff, you could do the same thing as i did and you can play with the sound that you like.
the baffle is two pieces welded together and i cut one section off. if you didn't care for the sound of it, simply weld it back on.
hope that help ya out....

 

yes a little. i've heard some will just cut the stock muffler in half
but i would hate to do that and discover i hate the sound.

i drilled holes (3/4") in the back plate but now it sounds like a sport bike.
a vary bad a$$ sport bike. but not the sound i want.

 

I think and always will think loud bike are for guy with little weenies. Whats the point. I do like a tasteful low rumble of a big bore bike but straight throughs just piss me off. I have a friend that rides a straight pipe bike and I refuse to ride with him because that noise drives me crazy. The sound of a small bore bike is just plain ridiculous anyone that like likes a straight pipe on a small bore has more than just one screw loose.
Put them on the bike and then spend 400 miles riding. Then you'll wish you never did it.

 

what you fail to point out is whether you compared weenies and found
yours to be the larger CC

 

Hey Parts,

I'm pretty sure what I have is a MAC header, this video gives a pretty good example of the sound (i think)

650

 

Thanks mwhite74..but the soundboard on my computer took a dive.
but i sure do appreciate the effort and wish i could compare sounds.

 

mwhite74, I like the sound of that pipe.

 

UPDATE; bought a pair of used srceaming eagles yesturday for $22.00.
there not in the best condition but should clean up nicely.

it was no fun trying to pull those OEMs after 25 yrs in the same place but
they finaly gave.
looks like the eagles inlet is much wider then stock (kinda figured that would be the case)so i cut the ends off the mufflers to use as spacers.
worked darn well except for a little wiggle that i'll fix with a couple of
exhaust clamps.

thanks for all the input... they sound great, and even look halfway decent.

 

this motor sounds better muffled.

 

can't speak for other xj models.but mine is irritatingly noisy.
all the wrenchers in the area say it's typical of these bikes ( i hate it ).
thats part of the reason for loud pipes.
plus i've noticed that the "you may not see me but you can hear
me" saying is true. with the stock pipes people pulled out in front
of me on an hourly basis.
now it rarely happens and i see other drivers turning their heads when
i approach.

 

hey parts, I have the same bike, its doesnt really rattle, it whines while drving cuz of the yics and the shaft drive, but it shouldnt really rattle....

 

speaking of weenie's, i think its the people that complain about other guys bikes being too loud. as the say's goes, if its too loud, your too old...
dont let the noise NAZI'S sway your decision.
its your bike, make it as loud as you can handle. im still trying too find the sweet spot on my exhaust. this is the video that made me go mac 4-1
8)





http://www.youtube.com/watch?v=he9LYO8b ... re=related

 

schooter...what rattle are you refering too?
i.ve read over my threads and cannot find a
mention of a rattle.

perhaps your thinking of another topic where we were dicussing
timing chain noises?