Changing the exhausts on an '86 XJ700

Well, I've been working on the forks lately and starting to look at the carbs for cleaning and such. As happens when you start pondering the manner of your bike, you start getting all sorts of ideas as to what you'd like to see change on it.

I came across some photo's of one dude's Xj700 and saw that he had removed the baffles and such and simply twisted all four pipes into a single pipe w/ no baffle. And this is very close to the idea I've been having about my bike (except, the single pipe would be pulled back and then come up like a diesel pipe on a tractor trailer in the rear).

My questions therefor would probably be...does removing the baffles mean having to change or tweak the carbs so I don't blow the engine? does anyone know or have done it yourself with removing the baffles in an attempt to get a more noticeable (ie- safer) sound?

Thoughts? Suggestions? Much appreciated.

 

Airflow and back preasure are the two issues... to get more technical the resonance and the timing of the pulses make or break a pipe.

Anyhow - you can do almost anything you want with the pipe, tuning it afterwards will be different than all of the rest of us though. IF you are comfortable tuning your bike then by all means go ahead.

Qute the endevor for a first poster - what's your background?

 

i'm getting there on feeling more comfortable about tuning the bike. what i don't want to do is cut off the pipes and find myself with a fine and troublesome mess. more the "think about it from 40 angles before doing anything" type of guy.

i had my first bike about 2 years ago - cb400. just something to tool around the neighborhood and town on, teach myself how to ride. sold it and bought my maxim last august.

i know that just about everywhere i look, all the maxims have some form of 4into2 pipes. so when i came across this one dude's ride and he had made it into a 4 into 1 - no baffles, just a short exhaust drilled many times, it really got me thinking.

by resonance and such, what exactly would i need to be looking at? my aim is to have my maxim be heard - partly for safety, partly for the sheer pleasure of it. and i really think the megaphone baffles look ridiculous the more i consider it.

 

On the being heard front - unless you point the mufflers forwards I don't think it's going to help you

Real basics of pipe design:
You want to setup a wave in the bike so that your low and high preasure pulses help as opposed to hinder the engine. Low preasure will 'help' suck the exhaust fumes out... flows more freely. This means you can put more charge in the cylander and get it out. Its fine to put filter pods on the bike, but if the limit is the exhaust side then a proper pipe will help get the ponies out.

An improperly tuned pipe will be a downgrade in performance - the sound might make it feel faster...

Tuning the resonance - well I have no wear near the technical skills to do this - but the idea is that you figure out what header lengths you need to get the pulses the way you want them...

For what you're doing:
If you start with the stock headers - then you're halfway there. If you start with a set of 4 into 1 headers then you're most of the way there.

Taking the baffles out will make the tail of the pipe flow better... but if the headers are the constriction then you've not changed the pipe that much ( you will have changed the resonance but fingers crossed it didn't matter ).

Long and short of it:
I'd suggest finding a parts bike with a ratty exhaust and trying it... I think it could work. I think it probably would work. It would be interesting to dyno the bike before and after to see what happened. You might be getting into carb/jetting work, but that shouldn't be too difficult.

Woot.

 

Have you thought about buy a 4-into-1 header system and modifying it? The header pipes and collector would mount to the bike and you woul be free to remove the cannister , modify the pipe end to the area and direction you want the cannister in and then reattach the baffle cannister.

 

i think what i'm gonna do is go tour a couple of the bike junkyards in the state and see if any of them have a 4into1 that would fit my bike and start tooling around on it.

from what i gather, i'm just gonna have to put it on and be prepared to start tuning the carbs so there's an even flow from intake to exhaust.

as far as resonance and such - i think that's way beyond my capabilities. but if i can get it to sound loud and mean without compromising performance, then my job is done. for this mod at anyrate.