exhuast

[kwikaz]

hey all does any1 know what the fibre wool inside the muffler is for?? that stuff that is around that tube with all the holes in it in side the muffler??

 

[motoluver]

Muffler packing... helps quieten the exhaust noise. Its usually fiberglass insulation but I just use housing insulation when repacking the mufflers on my 2 strokes.

 

[Sidney]

It's the baffle if you take it out you're gonna go deaf

 

[kwikaz]

deaf lmao

what ya mean go deaf?? i already am lmao, nah seriously i thought it might impact on performance like maybe make the valves run hotter?? or lose back pressure or somthn??

 

[motoluver]

It would... If you didn't have any that is.

 

[Mud_Skunk]

The fibre glass wool not only makes your bike quitter, it also has a predominantly deeper note if you leave it in, as it absorbs mid and high frequencies, thus letting low frequencies through.

Mine burn out so I only have 1 layer left... it doesn't sound as ballsy as my brother pipe, which is still complete.

 

[Pittin]

i took it out and it sounded shit lol

so i put it back in

 

[kwikaz]

muffler

you know whats funny the muffler just slides over the end of the exhuast pipe wierd?? so theres a unsealed conection between the two??

 

[Cactus Jack]

Mufflers are critical on two strokes because expansion chambers are sonically tuned - but they only serve to deaden sound on a four stroke - UNLESS they are a reverse cone megapahone type which accelerates cylinder scavenging . Once the gas is out of the cylinder - it's out for good on the 4's whereas 2's use back pressure to shove extra charge back in .

Look at speedway bikes - they used to run straight pipes but now they have to run a HUGE muffler because of noise laws . Drag cars run NO mufflers and they are built for maximum torque and HP and neither do a lot of prop aeroplanes which need maximum torque and HP .

Most people get their back pressure for 4 strokes ideas because they've altered a stock pipe without retuning the carb - which was already detuned to work with the back pressure of the stock pipe . If the head hasn't been ported , then the diameter of the header pipe on any replacement pipe shouldn't be much larger than stock . But then again - if you look at the '73 to '76 model XR75's - they had a big header pipe as stock - then in later years Honda made them smaller - coupled with a performance drop to go with it .

 

[Divy]

yeah ive got a 1975 xr75 cactus they do has a decent size header pipe but as the header pipe goes under the kick starter thhe size goes smaller