Originally Posted by Allen_Wrench
'Fraid he's right, Map. That expansion chamber is good for giving you torque where torque is usually lacking, but only at a certain RPM. In order for it to cover a RANGE of RPMs from high to low, it would need to change size, or to maybe work like a slide trombone (HEY! there's an idea! Maybe add a bi-metallic linkage to make it automatic! Hmmm...I wonder if there's money in that?) Anyhoo, it's still a good pipe, it's just not real adaptable.
I have no fuss about what Pablo said, I understand how the expansion chamber works and I know what it's advantages are under certain conditions all I am saying is that with my bikes I have not felt, seen or noticed any significant advantages to the expansion pipe verses the exhaust that I have built and put on them, top speed NO changemid range ????? maybe... NOT sure, low end torque, my pipes pull the hills better tahn the expansion pipe does in it stock length, this is the only point I'm making here, I have nothing against the expansion pipe and know that if it is tuned properly to a 2 smoker it does make a difference, I've had 2 stroke dirt bikes and my dad used to run the Yamaha 125 twins & RD 350's and I had an uncle that owned a Yamaha dealership and he raced the 2 smokers of the day and built some awesome racing engine so I have been around the 2 stroke stuff enough to know how it works, but these engines aint YZ 80, 125, 250 or the such and I dont find that the expansion pipe makes a noticable difference over my exhaust, now compeared to the stock exhaust the expansion pipe is far superior in every way but the 1" pipe on my engine does everything that the expansion does and maybe more as far as torque goes in my testing so far.....this doesnt mean that I may not find a sweet spot on that expansion and end up seeing a noticable increase over my home brewed pipe, but so far I haven't, that all I'm saying here.