Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Anyone know a bit about bike exhausts?

Discussion in 'Modifications and Projects' started by twr7cx, May 11, 2007.

  1. I'm looking at trying to improve the flow in the exhaust of my 2000 XR250R, but on the cheap. The bike is only used offroad these days, and here's two options I'm currently looking at.
    Removing the tailpipe and rear muffler and:
    1. making a new one up out of straigh pipe, so just free flowing pipe, no muffler to restrict nothing - wondering about noise but, would it be uncomfortably loud for me to ride maybe?
    2. fitting the Laser Pro Duro 'Classic' muffler (http://www.laserexhausts.com/en/product_info/produro.html and http://www.laserexhausts.com/dotcon...nfo/bikes/produro/LASER_PRODURO_INOX_05_b.jpg) I have sitting here that we pulled off a Yamaha 600cc road bike (although the muffler is an offroad orientated muffler).
    Just wondering if there's any concerns regarding these? I'm probably going to have both made up anyways to give tehm a go.
    I've been told that bike exhausts have different theories behind them to that of cars (which I'm used to playing with). One thing I've been told is that prior to the mufflers on a bike the pipe is usually flanged or coned and that helps with the extraction or drawing of the gases or something.

  2. Get a B&B alloy tip. It'll replace the stock baffle and while a tad louder, improves flow. Look on Ebay for a Staintune - they are the go. Take your headers off and grind any rough edges out - XRs notorious for these)
  3. Tell me more about this B&B please. I did a quick Google and hjust got bed and breakfasts.
    I've been looking at replacing the stock headers with a set of Staintune Big Bores, but I rang Staintune and they were unable to tell me the diameter of the pipes or the increase in size. No ways I'm working out $400 or what ever they are to find out there 1mm bigger!
  4. I'll remove the factory headers and take a look inside the pipe to see if there's any mess for me to clean. Is it generally at the side that bolts onto the head as that's where tehy'd have to fit the flanges right?
  5. just found this which is what i assume you were talking about
  6. When designing mufflers for Formula SAE (we used a CBR600 F4i motor), I recorded a baseline "mufflerless" noise output of 126 decibels @ 11,000rpm in neutral. Under load would be louder still. Instantaneous deafness can be yours for just a few decibels more!

    Suffice to say, not even foam earplugs will protect your hearing from that ballpark noise level. (When recording the sound levels I wore earplugs *and* earmuffs, and it still drummed my head painfully)

    Go for a straight-through glasspack muffler. :) It'll quieten the bike down to a relatively safe level and won't have any significant effect on power versus a plain tube of steel.
  7. Just remove the baffel completly or better still get a Staintune and get the jetting sorted as its not the pipe that restricting your bike its prob the main jet..and a good carby clean.
    A straight pipe u will loose some much torque and bottom end especially being a 250 it will be unridable.

  8. Sorry mate, been away with the pixies - here's B&B's link - ya needed to type in B&B aluminium
  9. Ok, so bit of an update. I've had a chance to play with the bike again, amoungst other things I looked at the exhaust. I removed the factory baffle as it talks about in here http://www.4strokes.com/tech/honda/xr250exh.asp . I then relised that my exhaust system is different to this - it seems the previous owner was already aware of this and has alread 'uncorked it' - but this comes as no suprise as I've already noticed that the bike is fitted with a uni filter and the air intake snorkel has been removed (also recomended on that site) and also a mate had a year newer (2001) XR250L and compared to his bike mine sounded anything but stock.
    Ok, so anyways I removed the factory exhaust tip end/baffler thingo (which I can't decide if its ever been removed before as it has two bolts holding it in and one original pop rivet - so I think someone started and then changed there mind or something). Anyways, both bolts decided they'd rather seize and snaped off leaving broken thread in there - so I'll have to drill and ezy out these later, and organise new bolts.
    So once I'd removed this, I decided to start the bike to see what she sounded like - at idle it was no louder, but was deeper, sounded awsome - like a small version of my old 300 Clevo (4.9L Ford V8). Gave it some small squirt of revs and ouch there was some noise there that my ears were not happy with - so I definately will not be considering a straight through pipe!
    Anyways, here's some pictures:

    And this is what I plan to fit now:

    More updates to come soon hopefully.