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Yoshi repacking, shorty conversion and a drainage hole (wtf)

Discussion in 'Bling and Appearance' started by Superunknown, Oct 16, 2008.

  1. Hey guys. I’m chasing a little bit of experience, knowhow and opinion. Please tolerate my ramblings, I’ll try to keep it short. Basically, everything started when I decided my exhaust was slightly too loud. I have an “insert-able†baffle*, but it makes the bike sound like a spitfire. I’ve never repacked the exhaust, and it’s done about 20,000 kms. So as far as I figure, a repack could cut down the noise.

    *I use the term “insert-able†because “removable†seems to imply that the baffle is usually in there :p

    Q1. Should I go get some proper exhaust repacking material, or are there better alternatives to cut noise? Can I jam as much packing material as possible around the centre pipe, or is there meant to be an air gap against the canister? I’m running a CF tri-oval Yoshi slip-on.

    In my research, I have come across a trend of chopping off some of the canister to make a DIY shorty can. They look especially cool, and I am very keen on trying this for myself. Problem is that logically, less muffling junk crammed into the now smaller can = more noise. Plus my hesitation to start hacking away at a relatively expensive can. Examples of DIY shorties can be found at:

    Q2. Anyone with experience/opinions on the DIY shorty? Wanna save me from a exxy mistake? The general consensus from my research is that shorties are louder than before, and yeild varying performance results (ranging from losing 10+ hp and low down grunt through to gaining hp).

    So I’m getting slightly excited now. This arvo I dropped into supercrap today and picked up rivets and bits to do this job. Putting away my shiny new riveter, I got skightly sidetracked and pulled off my exhaust just to have a look, as you do. The weird thing I noticed is that there is a 2-3mm hole in the inlet endcap, at the very bottom of the muffler. It’s fairly round, which makes me think it was purposefully drilled rather than a rust hole. Otherwise, if water got trapped in the muffler, this is where the rust spot would be.

    Q3. Is it common to drill a drainage hole in the a$$ of a muffler? It’s blowing a fair amount of air, and I suspect it’s the culprit for overlaying my beautifully bassy thumping exhaust note with a farting noise.
  2. A. Give me the bike and I'd happily keep it the way it is :p
  3. You say that now, but soon there will be that urge to tinker.

    I've seen stanless steel scourers being used to repack trail bike mufflers. Obviously this is not going to work in a CF exhaust because scourers will retain too much heat.
  4. he has already done it :LOL:
  5. Cheers for the reply. I take it i got no answers because it's been covered on here before (i found out after i posted using a less specific keyword search, sorry guys).

    I ended up getting a fair wack of fibreglass repacking material from Pro Honda for $30. Then i ripped off the muffler, drilled out the rivits and pulled it all apart. I cut 130mm off the pipe (just enough to get rid of the scuff marks) and managed to stuff almost all the packing intended for a fullsize muffler into my shorty. Plus i left the steel wool in there, i figured the more the better.

    It sounds awesome. Louder and deeper. Also it made the bike sound like stock with the baffle in. I'm very happy.

    I'm still puzzeled about the hole drilled in the back of my muffler though.