Motorcycle Repair: 1974 Yamaha Dt250 Tailpipe, warp engine, messy job

Question
Hi, I have a 1974 yamaha dt250. I've finally boiled down my excessive smoking
issue due to an almost fully clogged silencer/ spark arrester. What is the best
way to get rid of all the oil residue and carbon buildup  thats blocking up the
pipe? Also is is safe to ride without the spark arrester? Much thanks, Matt.

Answer
Matt,

the silencer on these bikes is usually
full of some fiberglass material and
it fills up with oil so bad that
the best way to insure they are clean
is to get a welder to cut open the back side,
dig out the fibreglass and wash out all the
old oil. I don't know of any other
way to make sure it's clean. Of course
it has to be welded shut again after.
It is optional to try to put new
fibreglass back inside.
It is a messy job but the bike will run
much better after.

-It is not good to ride without a pipe
because the cool air being sucked
in the exhaust port can possibly crack or warp engine parts.