the bike is a 2002 yz125. i just want to take a bit of noise out of it and was wondering if i welded a downpipe onto the silencer it would do that. we have an arc welder and a mig welder.
It's not going to change the decible output of the silencer, but it is going to change the tuned length of the exhaust.
A downturned tailpipe is an old trick that is intended to direct the sound towards the ground and diffuse it a little, thus making it seem a little quieter from a distance. In reality, it doesn't do much. And if you ride in areas that sound test, it won't change the test results one bit.
You could always fab the downpipe start the bike and just hold it there and see what you think. Maby tack it on to see if it effects performance. If not, wheld it on. It it does, try something else.