Two Stroke Motocross

Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: cnrcpla on September 18, 2012, 02:21:16 AM

Title: Expansion chamber design
Post by: cnrcpla on September 18, 2012, 02:21:16 AM
What is the difference between a 80's expansion chamber where it goes straight up and then straight back to the tail pipe vs. a current expansion chamber that curves under the kick starter lever and then makes the tail pipe bend up at an angle? Is it for more power or over-rev? Or something else?
Title: Expansion chamber design
Post by: TMKIWI on September 18, 2012, 08:48:18 AM
Just a funtion of design I would say.
As bike design changed so did the shape of the chambers.
Title: Expansion chamber design
Post by: 2T Institute on September 18, 2012, 10:31:05 AM
Quote from: cnrcpla on September 18, 2012, 09:21:16 AM
What is the difference between a 80's expansion chamber where it goes straight up and then straight back to the tail pipe vs. a current expansion chamber that curves under the kick starter lever and then makes the tail pipe bend up at an angle? Is it for more power or over-rev? Or something else?
Modern MX aftermarket pipe design is complete shit,As above the shape is merely for packaging.
Title: Expansion chamber design
Post by: cnrcpla on September 18, 2012, 12:29:17 PM
Oh ok, so if you could make it fit an old pipe could be run on a modern mx'r with out any issues I take it. Not that I have a project or something, I was just wondering hahaha
Title: Expansion chamber design
Post by: MXLord327 on September 18, 2012, 01:17:19 PM
I'm sure it is for proper fitment around the modern frames and much lower gas tanks, not for any performance gains.
Title: Expansion chamber design
Post by: lauterbacher on September 18, 2012, 05:22:30 PM
Does anyone have any links comparing old pipe design verse a newer pipe design? Pros or cons
Title: Expansion chamber design
Post by: Jeram on September 19, 2012, 01:34:57 AM
Older bikes for instance were air cooled so there was room to to up and over the motor as there were no radiators, this also kept the hot pipe away from the cooling fins

early liquid cooled bikes followed this methodology too, Im not really sure why... packaging for sure and perhaps crash protection

late model MX pipes are purely for packaging purposes and to minimise crash damage.
Heck you could get 10 more hp out of a 250 MX bike by putting an underslung large diameter expansion chamber on the bike.
only ploblem would be that you would crush the pipe the first time you landed a jump!

see what I mean?
every design is some kind of compromise or tradeoff
Title: Expansion chamber design
Post by: cnrcpla on September 19, 2012, 01:58:55 AM
Great info guys  ;D I love having this site to ask these random questions I get from time to time  :P I know my pipe goes up to the top but it has a curve to it. I have got to find a way to get one of the dents out, it's not huge, but its bothering me. I heard of this freezing method but wouldn't that pop the welds? I mean ice pressurizes the whole pipe not just that one area. I also heard of the pressurized air and torch method, that one I may try. Would oxcetoline be to strong for that? I don't a hole in my pipe or a bubble hahaha
Title: Expansion chamber design
Post by: SachsGS on September 19, 2012, 02:49:21 AM
Manufacturers lowered the exhaust (and gas tank/rads etc.) to lower the C.G. of the motorcycle to make it more responsive to turning.
Title: Expansion chamber design
Post by: Jeram on September 19, 2012, 04:18:24 AM
Quote from: SachsGS on September 19, 2012, 09:49:21 AM
Manufacturers lowered the exhaust (and gas tank/rads etc.) to lower the C.G. of the motorcycle to make it more responsive to turning.

There we go :)