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Old 07-10-2010, 03:40 AM
BarelyAWake's Avatar
BarelyAWake BarelyAWake is offline
Motorized Bicycle Elite Member
Join Date: Jul 2009
Location: Maine
Posts: 7,212
Default Re: Whats the difference?

Well a "tuned pipe" itself doesn't muffle or silence at all so it would depend entirely on w/e muffler it came with or you stuck on it - but to answer your question anyway, even if you stuck the stock kit muffler on an expansion chamber/tuned pipe it would be slightly louder (but really, only slightly) as the larger chamber (usually with thinner walls, but not always) resonates.

The trick of it is ofc to get a full length exhaust system and add/modify a silencer to suit. This not only quiets the noise considerably but puts most of it behind you as well, resulting in a far more comfortable ride. Problem is, most expansion chamber exhaust systems don't have much in the way of a silencer - if any at all. You wouldn't actually wanna stick the kit muffler on it because it's either a baffle style or a catalytic - both restrict flow to quiet the bang.

Some expansion chambers come with a glasspack silencer which, while not known for being the best at sound deadening - aren't restrictive in any way, but for our application & pipes available they tend to be a touch on the small side and aren't as effective as they could be. While some have taken a small lawn mower/utility engine muffler and stuck it on the end - we're back to restricting flow.

Glasspack muffler/silencer;

One of the advantages of a glasspack is it's quite easy to modify, the SBP expansion chamber comes with a lil glasspack on the end, it's simply a matter of drilling out four rivets, extending the inner mesh tube (heavy steel window screen works quite well), wrapping it in fiberglass (either the mat usually used for epoxy construction, or even house insulation if the screen is fine enough) and making a new outer housing out of 2" OD aluminum conduit, then poppin' four rivets back in again.

My homemade/modified glasspack is about 3x longer than the original and is now actually a bit quieter than the stock kit muffler (a LOT quieter for the rider as it's behind ya);

The only disadvantage to a glasspack is it will slowly load up with unburned oil & carbon and be reduced in effectiveness - so (depending on your mix) a repack once a season is needful if you wish to remain as quiet as possible

Last edited by BarelyAWake; 07-10-2010 at 08:49 AM.
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