exhaust modification

[NakedLeo]

i have a 70 sport malossi bbk and here is the exhaust i have (some cheap chinese) 
i took the silencer off and felt a little restrictor at the start of the bend where the pipe goes to the silencer, so i grinded the bend off and got the restriction out and now im wondering if i should bend a new piece that will be bigger and allow more air into the silencer.

 the stock piece that i grinded off was 12mm in inner diameter and the new one is 23-25 inner diameter if i remember correctly 

i dont know anything about exhaust things so it would be nice if someone could help me 

[190mech]

Those are some awful pipes!They just jamb the tubes in and weld them,everything inside of a good pipe will have smooth transitions,,the head pipe is the same way on them..For a 70cc you want around 21mm OD(19MM ID) to keep the CHT temps in check,,An old road bicycle handlebar makes an ideal tailpipe(stinger) for that size engine..

[NakedLeo]

Thanks!

[gerson4100]

opa, boa tarde, teve um bom resultado tenho em escape desses e estou pensando em fazer o mesmo mudar o stinger dele, como ficou o seu?