new idea
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new idea
i was just brainstorming and came up with this idea in school (nothing better to do). i was gonna pull the muffler off my spree to try to make it faster.it seemed to work well on my friends spree.i was gonna make a special hedder as well but i am gonna use this daily and cops tend to like the idea of mufflers.anyway i was gonna take a 1 inch diameter y valve and use it as sort of an exhaust cut off.what this would do is allow me to either run with a stock muffler or a straight pipe.(you know to * off the neighbors i just dont like)
The pipe need to be the right length, and needs to choke at the end to a smaller pipe. It's not static backpressure that it needs as much as the right length so that acoustic waves hit the end of the pipe and bounce back at the right frequency, "plugging" the exhaust port with a pressure wave and keeping the fresh inlet charge in the cylinder.
All that said, the pipe should be about the same length at the current muffler. I would choke the end with a 1/2" ID pipe, which is slightly larger than the current choke pipe. 1" ID sounds about right for the expansion chamber.
If you want a better (harder to make) design to try, let me know.
As for noise, you should be running a silencer, which is constructed much like a "cherry bomb" muffler. This won't have restrictions, will be louder than stock but quieter than not having one. Moped speed shops should carry these...
All that said, the pipe should be about the same length at the current muffler. I would choke the end with a 1/2" ID pipe, which is slightly larger than the current choke pipe. 1" ID sounds about right for the expansion chamber.
If you want a better (harder to make) design to try, let me know.
As for noise, you should be running a silencer, which is constructed much like a "cherry bomb" muffler. This won't have restrictions, will be louder than stock but quieter than not having one. Moped speed shops should carry these...
BTW, as for adding "lake pipes" to your Spree, funny idea, won't work unless your cutoff pipes are the right length, and choked. Remember, this is a 2-stroke, so the pressure conditions at the exhaust port are critical. There's no valve to close off the port.
The Spree shouldn't run very well with the exhaust removed, it should just be really loud.
Below is a completed auction on a expansion chamber/silencer design. This is what a decent design should look like.
http://cgi.ebay.com/ebaymotors/ws/eBayI ... 2492600941
Note the front and rear tapers; this allows the design to work across a wide RPM band, vs. a narrow band that you'll get with a straight pipe. Note the attached pass-through silencer; less backpressure. Most of the designs I see seem to have too large an expansion chamber; I think it's done for looks. The tuned and choked straight pipe would probably be a good starting point for the Spree. You could play with the length until you get what you want in terms of driveability. And it will sound meaner.
I think if you used the Spree downpipe and just cut off the muffler box and attached the 1" ID pipe to that, choked at the same overall length, you'd have a good starting point for the design. You could then play with tapering the rear section to the .5" rear outlet and adding a silencer. I would fold the silencer above the pipe as shown, or just outside of it.
The Spree shouldn't run very well with the exhaust removed, it should just be really loud.
Below is a completed auction on a expansion chamber/silencer design. This is what a decent design should look like.
http://cgi.ebay.com/ebaymotors/ws/eBayI ... 2492600941
Note the front and rear tapers; this allows the design to work across a wide RPM band, vs. a narrow band that you'll get with a straight pipe. Note the attached pass-through silencer; less backpressure. Most of the designs I see seem to have too large an expansion chamber; I think it's done for looks. The tuned and choked straight pipe would probably be a good starting point for the Spree. You could play with the length until you get what you want in terms of driveability. And it will sound meaner.
I think if you used the Spree downpipe and just cut off the muffler box and attached the 1" ID pipe to that, choked at the same overall length, you'd have a good starting point for the design. You could then play with tapering the rear section to the .5" rear outlet and adding a silencer. I would fold the silencer above the pipe as shown, or just outside of it.
ok, i dont thing i am going to try this till i get a beat up muffler. my muffler is in suprisingly good condition, so ill wait.thanks for the tips tho.it would probably work if i just welded in a washer with a 1/2 in dia hole wouldnt it?that way if it is too much restriction i can always make it larger. did u finish upgrading your iowa yet?i saw that you had it bored out.
I'm still playing with the Iowa. I bought another intake runner (carb to reed valve) to re-port that part.
If you look on the side that the carb attaches to, the inlet jumps down from the 17mm dia to a much smaller throat. In my mind, you want a nice, even expansion of the inlet after the carb's choke point, so I've been hand-filing the part out to lessen the choke point there. If it helps anything I'll post what I did. Either way I'm only out $2 for the part and about an hour with some riffer files (small curved/contoured files.)
If you look on the side that the carb attaches to, the inlet jumps down from the 17mm dia to a much smaller throat. In my mind, you want a nice, even expansion of the inlet after the carb's choke point, so I've been hand-filing the part out to lessen the choke point there. If it helps anything I'll post what I did. Either way I'm only out $2 for the part and about an hour with some riffer files (small curved/contoured files.)
New Idea
My friend and I made a custom pipe for my 86 Spree by combining a YZ85 stock exhause pipe and a YZ250 aftermarket Pro Circuit pipe. The way the exhaust pipes are set up for the Sprees, is for 4 strokes, they don't have chambers. After taking the stock pipe off of the Spree, and putting the new made pipe on, the Spree went 9 mph faster! So keep stuff like this in mind when up are making your own pipes.
Good Luck you guys!
Matt Kruger
Good Luck you guys!
Matt Kruger
