Straight-piped GX340

[Doc Sprocket]

Hey, y'all! I want to make a custom exhaust for my kart, so I started by making a flange and attaching a 1"EMT 90* elbow. Since I haven't decided what to use as a muffler yet, I bolted 'er on and had a go. Wow! This little video clip shows a couple of rev's, but when I took it for a buzz- OBNOXIOUS!!! My wife was just shaking her head.

Any (cheap) suggestions for a muffler?

http://www.youtube.com/watch?v=_ANonENmySw

 

[devino246]

Got an old propane or mapp gas tank? http://www.diygokarts.com/vb/showthread.php?t=6887&highlight=homemade+muffler Only takes an afternoon to make. The best part is, its FREE

 

[NapO]

just curious, whats the top speed of ur kart?

 

[Doc Sprocket]

I just clocked it yesterday, average top speed in 3 passes was 72km/h (45mph) according to my GPS. I stayed at full speed for well over a minute each pass to let the GPS stabilize.
I have GOT to rig a speedo, or make a gps bracket for testing. Trying to drive this beast one-handed, while hanging on to the GPS for dear life at 72K over potholes and s**t on a gravel road is f**king spooky!!!!!

 

[vgk]

I do that with no seat belt!

 

[Doc Sprocket]

Dood, yer nutz. I just tore out my lap belt, and installed a shoulder belt assembly I pilfered from my work van, a 2001 Pontiac Montana. (Left rear seat). Works great!
Did it mainly 'cuz I got no suspension, and get tossed around BAD when offroading. I originally installed the lap belt, because the bumps were almost throwing me out of the kart!

 

[KieranM]

I would not put a muffler on it, it sounds savage. What i would do is put a small piece on the top to stop rain and dirt getting into you a chamber. Like on most straight piped older tractors.

 

[Doc Sprocket]

It does sound wild, but it'd loud. My neighbour's a cop. A nice guy, though, and I don't want to pi$$ him off. I was thinking about a cherry-bomb type setup. I could drill a bunch of holes in a pipe, wrap it in fibreglass, mineral wool, or steel wool, and pack it into a can. It would still be straight-through, but a little quieter, I think. Ideas?

 

[Kenny_McCormic]

Ask the cop what he thinks? Just setting it up to point down helps.

 

[devino246]

Use my setup. Take a piece of pipe, cut it in half. Then drill holes in each side. weld the 2 halves back together, but with a piece of metal between them. Then slide it in to your muffler shell of chosing and you have a semi quiet muffler that still sounds cool. I did it, it works great.

 

[Doc Sprocket]

Is there any kind of packing in the can, or is it just open inside?
The cop's a really nice guy, but I don't want to push my luck. He's been asking about the kart, showing some curiosity. I'll see if I can warm him a little by offering him a spin later...

 

[devino246]

No packing. The piece of metal between the 2 pipes prevents the air from flowing straight through the pipe. The exhaust is forced to flow out though the holes drilled in the pipe and into the muffler body. Then the exhaust just flows into the other pipe and out of the muffler. Alot of lawnmowers use this design, i just supersized it so there would be less resistance. I think the theory is that the noise eccoes in the muffler and cancels its self out.

 

[newrider3]

For an engine that size, a small dirtbike silencer would quiet it down a bit and still sound cool. Would look neat too.

 

[Doc Sprocket]

Thanks, fellas! I think I'm gonna give devino's plan a go, it'll cost me nothing. I've got some old fire extinguishers and things laying around I can use. Probably crack into it next weekend. I started rigging a bicycle speedometer today, but didn't finish because I had to got trucking off to a family easter thing. Dang. Cheers!