XJ900 Backpressure

Hi,
I was hoping someone could measure me up the original hole diameter on end of the twin exhausts from a standard XJ900 seca?

I have a 4into1 on mine and I'd like to try and replicate the original back pressure of the original system and I'm pretty sure that huge, howling exhaust pipe hole just isn't close.

Thanks!

 

The diameter at the end of the Exhaust Silencer has less to do with the Back Pressure as does:

a) Slots and deflector within the Exhaust Collector, ...
and
b) Restriction Plates, Flow Pattern Deflectors and Perforated Tubing within the Silencer which the Exhaust passes through before reaching the Exhaust Pipe.

You might be able to add Baffles to your System that would help some:

http://www.jpcycles.com/product/442-830 ... ap=442-830

 

Rick is right. When it comes to the collector-box exhaust system equipped bikes, you can pretty much pull the mufflers OFF without greatly affecting tuning. On those bikes (XJ550s, XJ650 Seca, the 750s and the 900s) the collector box was a major part of the "magic."

The hole in the end of the mufflers won't matter much.

 

then I'm gonna go put some cobra long-shots on my 700 pseudo-bob. Nah, just kidding.....but I am gonna put some straight pipes w/ turnouts on

I have to swap to the shorter shocks yet, and tilt the bars. But, the shaved seat is back on and I re-stitched the seams so all looks good there. The bobtail fender looks good, too.

Will get a pic up when I can.

Dave

 

Makes purrfect sense... although i wish this thing purr'd more than it howled!
After a bit of messing about it seems i have other issues related to the 750 airbox on the 900 restricting the flow in also.

So in saying that it looks like the backpressure isn't an issue at the moment... just the racquet it causes.

and Thanks for the advice.

 

You could get a few stainless steel kitchen scrubbies and secure them in the beginning of your "muffler" for some sound reduction and back pressure.

 

Finally sorted it out!
Came close to the SS scrubbies suggestion but in the end I found this little beautie on gumtree the other day and after modifications it is so quiet the engine sounds a bit like a blender with nuts and seeds in it.

I have to paint that adaptor and extension the same colour as the 4into1 pipes still but...

Kawasaki Titanium muffler $30... getting rid of that piercing howl - priceless!


One thing I absolutely think are the best are these clamps that the exhaust guy, who i bought the pipe from, suggested from enzed. Stainless steel, metric, damn sexy.

 

What was the muffler you had on it before that you weren't satisfied with?

 

This one. Pipeline I think the sticker reads. Pretty much straight through if you look inside it.

 

Mine ran like a bucket until i closed the centre pipe and repacked with fibre glass. Wasn;t just loud it sounded horrible. It likes to have a bit of backpressure, much happier, plus i can hear my music now
PeterN