DIY Mini Bike Glass Pack Style Muffler/exhaust

[nightgrider]

Has anyone on the site tried making their own glass pack style muffler/exhaust system for their mini bike? I've been kicking the idea around for a while, but haven't started on anything. I'm picturing a pretty basic style muffler/exhaust when finished all one welded piece. A tube (header/exhaust pipe/tail pipe) pre-bent with holes drilled in the "muffler" section, then a muffler body made from a larger diameter tube and welded with a cap around the perforated portion, then packed with fiberglass packing, and welded up to finish with another cap. I know a lot of work, when there are so many inexpensive header pipes and mufflers available online. But sometimes my mind wanders or your shooting for a certain look for the exhaust. I'm also just curious what one would sound like.

 

[Minimichael]

I want to know, too

 

[SAS289]

Well. I can tell you it should sound good but will be loud with RPM.

Pictured is the homemade mess I had on my 196. I used 3/4" for the header. I got the glass packed "silencer" from JC Whitney back in the late 90's for my old RM250 dirt bike. All I heard was "Why's that thing so loud?". Same way on the 196 just not 2 stroke loud. Was kinda fun to make but I'm no longer using it. That engine now has a stock 224 muffler.

 

[nightgrider]

Well. I can tell you it should sound good but will be loud with RPM.

Pictured is the homemade mess I had on my 196. I used 3/4" for the header. I got the glass packed "silencer" from JC Whitney back in the late 90's for my old RM250 dirt bike. All I heard was "Why's that thing so loud?". Same way on the 196 just not 2 stroke loud. Was kinda fun to make but I'm no longer using it. That engine now has a stock 224 muffler.

View attachment 300584

Nice! Do you remember how long the "muffler" was?

I assume length, diameter, amount of packing, tail pipe length after the "muffler", and engine size will all affect tone/level of decibels.

 

[SAS289]

It's 1 1/2"x 9". What's interesting about it is the inlet is bell shaped and goes smaller than 3/4", probably 5/8". My 3/4" pipe mates into the bell. It worked ok but not an ideal design on my part. I didn't weld the inlet and there's no way it could have been run without that long brace from silencer to the head. The silencer is fully serviceable for repacking.

I have a 1" short header and a mini 91 on my 224. The glass pack set up on my 196 sounded better. Difficult to describe.

 

[creia]

Nice! Do you remember how long the "muffler" was?

I assume length, diameter, amount of packing, tail pipe length after the "muffler", and engine size will all affect tone/level of decibels.

By definition- "glass-packs" are VERY LOUD.
Michael

 

[nightgrider]

By definition- "glass-packs" are VERY LOUD.
Michael

Most definitely. This is mostly just an exercise in my mind wandering. I just think the tone would be interesting, but without quite the decibels of a straight pipe. When it comes to exhaust tone and loudness everyone has their own personal preference and limit to what is acceptable. Of course external limitations also can affect that such as neighbors etc.

 

[cattailhaas]

Yes I made my own, only I used steel wool for the packing...

 

[nightgrider]

Yes I made my own, only I used steel wool for the packing...

Nice! Turned out really well.

 

[Minimichael]

How often ya think a mini would need repacking? I imagine the material could get gunked up.

 

[DaddyJohn]

I like the sound of a regular Briggs hot dog muffler with the center partition drilled through (I hammer a taper punch through it and open the hole to about 1/2”).

 

[Minimichael]

I've been using the bigger Briggs hotdog mufflers (3/4" mount) on my smaller 2&3hps. Sounds bigger and bolder! Agreed with @DaddyJohn, too. The punch hole adds something to the pitch of the sound.

 

[Minimichael]

Speaking of hotdogs, I found this on the bonanza auction site. It's about a foot long and I'm looking forward to it running on a Briggs 5hp this summer, fingers crossed. And my apologies for hijacking the thread...

 

[Minimichael]

Back to the glass pack idea, I would love to have a way to turn my mini bike sound way down. Sometimes... Kind of depending on what time of day and where? I'm at riding around the neighborhood. Seems the custom auto market has managed to tune for some of the best qualities of loud vs rumbly, warm vs cool, etc.. It would be cool to cruise around on minis and not have it be a noise racket coming down the block every time. Hey, how about a remote controlled baffling assembly? Or some sort of a movable vane you could adjust for time of day, parade route, mood of the event...

 

[nightgrider]

Back to the glass pack idea, I would love to have a way to turn my mini bike sound way down. Sometimes... Kind of depending on what time of day and where? I'm at riding around the neighborhood. Seems the custom auto market has managed to tune for some of the best qualities of loud vs rumbly, warm vs cool, etc.. It would be cool to cruise around on minis and not have it be a noise racket coming down the block every time. Hey, how about a remote controlled baffling assembly? Or some sort of a movable vane you could adjust for time of day, parade route, mood of the event...

I know of the type of variable tone mufflers you are referring to. I think the biggest limitation for a mini bike is available packaging space for even a custom built muffler of that style. The easiest way would be like an old school exhaust cutout just before the muffler. So when you want it loud you open the cutout to bypass the muffler and when cruising you close the cutout to direct the exhaust into the muffler.

This is probably a personal opinion but I've never classified small engine exhaust as very quiet. Definitely more quite than straight piped, but usually can still be heard from about a 1/4 mile away. It's just their nature of necessity to be compact, for multiple application use. A small muffler body and short exhaust length (header/tailpipe, if any) just doesn't provide the time for the sound waves to flatten out (for lack of a better word). The stock clone style mufflers are some of the more quite small engine mefflers I've heard.

Now that I'm off my soap box. Definitely mini turbo style, laminar flow, glasspack, or chamber mufflers could be custom built. I think it's mostly the demand just isn't there. But definitely would be interesting to see the outcome on tone and decibel levels. Now we're starting to go down the exhaust science rabbit hole. Lol

 

[DaddyJohn]

It would be easier to do something like the Supertrapp “Snuff Or Not” concept with an adjustable end cap.

 

[nightgrider]

It would be easier to do something like the Supertrapp “Snuff Or Not” concept with an adjustable end cap.

Interesting, on setting three is it completely closed or does it have other opening to let exhaust out?

 

[DaddyJohn]

Interesting, on setting three is it completely closed or does it have other opening to let exhaust out?

On the Supertrapp mufflers, there are permiable stacked disks sandwiched on the end of the muffler for the exhaust to pass out of. The more disks, the greater flow. Normally, the end cap is solid, but the adjustable cap (as pictured) allows a bypass of sorts. If you didn’t have the Supertrapp style muffler, you wouldn’t be able to make a cap that shuts completely.

 

[SAS289]

I would get a SuperTrapp if they didn't cost so much. I just can't see paying that much for a mini bike muffler.

 

[DaddyJohn]

I think it would be possible to do something like that with a regular style muffler to quiet it down here and there, though granted, it’ll reduce flow and affect optimal jetting.