Blaster w cbr929 exhaust

[Larry's Shee]

The "baffle" in the stock silencer is part of the spark arrester system. The transfer action you are describing happens way up in the expansion chamber.

Here's a good read on exhaust theroy and design : http://www.amrca.com/tech/tuners.pdf starts on page 52
H. Grahm Bell might also have useful info for you.

Without EGTs/dyno to help "see" what more back pressure is doing (or not) it's risky at best. To much backpressure will melt a piston just as fast if not faster than lean jetting or air leak.

Aftermarket silencers use no baffle, if spark arrested they use a SS screen that's cone shaped.

 

[Weelys4days]

Thank you for the link, there's a lot of good info in there. From what he says, using a straight through muffler shouldn't have any adverse effects as all of the backpressure is made by the expansion chamber. This is where I'm hearing mixed info. Some info I've read says that the entire exhaust system creates the necessary backpressure, and other sources have said only the expansion chamber creates the backpressure. But I believe I'm going to follow the tuners handbook finish my jetting and let this beast rip! Once I get finished with paint that is.... This thing is practically a whole new machine since it came into my possession, and I love it!

 

[rich1]

I have that book and have used it for years ,even though it is now a little dated . The real info you seek is in Chapter 4 Exhaust on page 87. It shows the tube size in relation to the stinger that's used and is not baffled .

 

[Larry's Shee]

To an extent, both are correct. It's a tuned system. From the port opening to the tip, wether open stinger or silenced. Most stinger/silencer combos are slightly longer than the "formula" would call for, so the diameter is increased slightly to compensate. Granted there have been improvements with time, but basics are same.

Bimotion has a program you can buy that you just plug info in and it will spit out a design.

Would be nice to find a cone maker that had reasonable prices. Making your own cones is a rough road.

 

[Weelys4days]

Rich1 I looked everywhere for that info and could not find it. In the link larryshee sent me the only thing relative to exhaust is the section on expansions chambers. It there any way you can scan that page from your book so that I may read it? I tried to read it from your picture but it was a bit too blurry for me to see on my phone. Thank you everyone for providing me with a little extra reading material, I've learned quite a bit more about 2 stroke exhaust after reading an in depth explanation

 

[Weelys4days]

As it turns out I managed to scoop up and old lrd adjustable expansion chamber which just came in today. Got it all together and ready to start jetting tomorrow, what do guys think about these lrd pipes?

 

[Blaaster]

LRD are pretty honest pipes, fairly good power gains.

Beware of the adjustable leaking it can really throw the jetting off!

 

[Herpderplol]

problem with those pipes is the leaking. and its impossible to install in the frame put together (or for me it was)

so sealing it is hard, but make sure its sealed well

 

[Weelys4days]

Yea I assumed leakage would be a common problem , and mine also had to come apart to install it. While it was apart I had a good chance to clean all of the old gunk off and put some fresh exhaust silicon around the connection points. I didn't get to ride it yet since I was waiting for it to dry, but I'll try to post a good video when I get it completely finished.