2 Strokes Down Under

ok so a lil while back in the quest for a better performing pipe for my dt200l. i modified a cr125 DG chamber to fit...it was ok..it felt the same off throttle and had much improved top end ..but i lost all my midrange.. after a full days hard ridding i ended up swapping it back to stock.
after some reading and comparison.. the dt pipe was much longer in the header and the cr reasonably bigger in the expansion part of the pipe..so today i married the two together..
when i cut open the dt pipe i was amazed at how much matting and gauze was welded to the inside...and the was a funnel in the middle of the chamber as well...
i also used the end diffuser cone and stinger from a spare rg250 pipe i had this all matched up nice...but again once when i cut open the rg pipe i found mesh welded not as full on as the dt pipe but still a full layer covering the entire inside...also it was amazing how much carbon build up there was in the rg chamber easily 5mm thick..!!!! thats what you would expect from all pipes of that age...cant be good for performance..!!!
any way i welded the pipe all up and put it back on the dt...and its feels great so far... i could not really get a good test as it was raining and i have full knobbly tires... but i have the top end back with out the loss of mid range wheel stands..!!! and it doesnt sound like a tractor at idle now either

Hey twinrock. Did you leave the mesh and gauze in place or did it inadvertantly get left on the floor of the workshop just before the pipe got welded back together?

ok ill clarify a bit more...
the end result was a pipe built from 3 different pipes..
the header pipe from the dt right up to the expansion chamber this although double skinned has no mesh in it..i discarded the rest of the dt pipe which contained the heavily meshed walls..

then i cut the mid section(expansion chamber) from the light weight, unrestricted DG cr125 pipe and welded it on..

then i used the difuser and stinger of a rg250 mk1 pipe.. but i removed all the mesh
here is a pic it will make more sense u can obviously see the 3 sections
http://s36.photobucket.com/albums/e47/t ... 020274.jpg

Dyno before and after. ?

well hard to dyno befor as i have cut the original pipe up...but there is def more power every where now..but more importantly top end...
riding on the weekend with a mate on rz350... in a drag race there really was not much in it..the rz350 pulling away... but not left behind.. dt out ran suzuki gs500..!! obviously the dt runs out of breath at 130 or so..but man i was sitting at 110 going through twisties all day..!! no probs

My surprise after removing the mesh and bands from the RG pipes was how little difference it made to top end power. The improvement was in the midrange. And most of that was probably due to the extra pipe volume.

OK.
The header is followed by the diffuser then the belly and finaly the baffle cone. There is no 'expansion' part of an expansion chamber.
Heat and changes in cross section make a chamber work, getting rid of the gauze lets the heat get into the pipe, which makes it come on earlier. Larger diameters make steeper cones which favour short high amplitude waves, which work at best at high rpm.
Standard DT 200 pipe is worth a fortune in scrap value there must be nearly 5kgs of metal there.