How to clean exhaust?

[mad_max]

Im wanting to know if theres any tricks to cleaning my 89 YZ125 expansion chamber. Its got a bit of crap in it and I want to clean the whole bike up.
Also I want to know the best way to seal a little hole in it.
Any hints or tricks?

Cheers

[SMOKEU]

If you have access to an oxy acetylene welder, then heat the whole exhaust up until it's just starting to get red hot, then turn off the acetylene and force heaps of oxygen through it to burn what's inside.
Alternatively, if you have a wood BBQ or other such fire place, even a brazier will be mint, then make a big fire and put the exhaust in there for a few hours. I did that to my 2 smokers scooters exhaust and there was smoke coming out of the exhaust for over 2 hours from all the shit that was burning inside it.