Hello
I am trying to de-clog my silencer. I was wondering if the center should be totally unobstructed?
This bird on utube just drills a hole through the center, is that right?

I am currently soaking mine in simple green and it is making a little bit of progress.
 
​​​​​​I plan to take a torch to it tomorrow.
 

Video isn't working for me...  probably my connection.

Anyway no.  Center is like a "cone".  Whole thing looks a little jet turbine-ish.  If you start knocking holes in it you'll destroy the spark arrestor which could get you a ticket or impounded depending on where you ride.  Worst case would be starting a fire or something. 

Some have used a modern FMF turbine core muffler to replace those if you want something modern that might flow better and be easier to maintain. 

Heating the heck out if it in a fire or barbeque or with a torch will turn the crud to ash and it will just shake out.  Like red hot or near it.  When using a torch if you can blow air in it, often you can get a fire started inside if oily and it will burn from one end to the other...  I've managed it a couple times and it's pretty cool how a red hot ring will travel down the muffler as you feed it air...  smokes like heck though. 

Ok 
​​​Thanks!
seems the video only plays in utubeBut basically he dills a 1/2" hole through the center of the silencer, to improve how the bike runs.

That "mod" will make the spark arrestor illegal and ineffective...  your bike and your choice...  if you think a ranger or LE will be fooled by the stamp on the muffler, they won't...  they have a test rod they stick down the pipe and with a hole drilled it will fail.

Yep, the risk reward is not there-  We have seen way to much destruction caused by fire to play around with that. 
but just to be clear, so I know that its clean, is it a mesh like a modern spark arrestor or solid metal?

If you can't get the torch to work or its too smoky I've had decent results with Sears Kenmore Gas Grate cleaner...  a powder you mix with hot water in a bucket and let it soak overnight.

If they still make it and it hasn't been "reformulated" to where it's useless and won't cut through the grease and carbon.  Do not use on aluminum!

It is a modern spark arrestor design...  a GOOD one!  Krizman design that does not use any kind of screen!  (brand new FMF Turbine core is the same design).  It's basically a centrifugal trap....  the carbon particles get blown through the "turbine blades" you see down there which throws them to the outside of the can.  The removable insert has a plate and the outlet pipe in the center the sticks through the plate a little.  Exhaust goes right out the outlet but heavier particles are trapped.  Removing the insert allows you to dump out any carbon particles. 

Brilliant design that Yamaha chose to use instead of the simple cheap screen. 

Screen arrestors are crap on two strokes and Yamaha never used them. 

 

Pictures are worth 1000 words...  Duck Duck Go came up with this result.  Scroll to the very bottom and you can see a cutaway and click on links to see pics of inlet and outlet. 

Not a Yamaha but the same exact design. 

clemelis.synology.me/planetklx/techtips/exhaust.html

Yep video played ok on youtube. But i guess we're in a different world nowdays & in my previous life we just used to knock them out by smacking in the middle to break the spot welds the shake it back out the end or grab it with long pliers if i recall right. Then it became louder & faster--if it was blocked. Best to carry on with the burning out from one end to the other of that muffler as grows in the pipe too that's part of that muffler. Know anyone with a log fire!!. I wonder about the complete system when you see that in the muffler, although that muffler belongs to the original DT pipe?.