Quieting 2T expansion chamber ping?

[heart_of_darkness]

I hate to lose the two smoke music, but I need to make my CR250 significantly quieter. I got a quiet muffler, and now it seems more noise is coming through the wall of the expansion chamber than out the tail pipe.

I don't think that anyone makes a double walled pipe for the CR250. Has anyone tried the woven fiberglass header wrap? Are there any other tricks?

[KcDavis]

Header wrap is more so for heat rather than noise. Since the silencer has gotten quiet, you are now hearing more engine noise. I don't think there is much that can be done about engine noise, unless you keep the engine off. If you are hearing exhaust, maybe check where the pipe connects to exhaust port and make sure there is a tight seal.

[xrrider250]

my brothers yz is like that. we re-packed the muffler and most of the noise emission now seems to be resonating from the walls of the well.. resonator. trying header wrap couldn't hurt i guess, though I've heard people get corrosion problems with it. if you dont mind me asking, why do you need it so darn quiet?

[RDZombie]

im all abou stealth on the trails. i whent for the FMF Q on my cr250, also got a gnarley pipe which is a little thicker walled than a standard fatty. also picked up an eline CF pipe gaurd and while its still not as quiet as id like, the gnarley/pipe gauard combo did help a little with chamber noise.

[Dac1915]

I know the RMX and KDX stock pipes were double walled (and heavy as heck) inorder to keep the sound down, maybe you could cobbing something up.

[rpt50]

I noticed that you are in Virginia. Just wait until the leafs are back on the trees. That smoker sound will be sucked right up by the vegetation. My Cr 250 did seem to have a lot of mechanical (non exhaust) noise, but one other thought--are you running an aluminum skid plate? They reflect a lot of noise up and out.

[heart_of_darkness]

The sound I'm trying to quiet is the distinctive tinny, almost metalic ping noise emenating from the pipe walls. With the bike on a stand, I can walk around it and distinguish the engine's mechanical noise, the whoosh of the exhaust out the tailpipe, and the now very dominant ping from the expansion chamber. It's kind of cool to hear the different noises separately.

I got the fiberglass header wrap idea from http://www.yellowdogracing.com/deztaz/quiet.htm. I wonder if the corrosion issue can be solved by saturating the fiberglass wrap with fiberglass resin, essentially 'glassing the whole pipe. Although the resin would probably burn from the exhaust heat. If carbon fiber pipe guards survive, I wonder if the entire pipe could be wrapped in CF. Maybe the CF ricer look will become a fad...

I'd like to fabricate a complete outer sheetmetal shell, but I'd have to sacrifice another pipe to get outer halves that match the same complicated contour. From what little I know about accoustics, even small gaps or holes let out a disproportionate amount of sound.

[cr 250]

the db snorklel!

http://www.thedbsnorkel.com/

i know its for muffler but i've heard it makes the bike very very quiet with little to no power loss