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Silencer core

  • Jack
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Silencer core was created by Jack

Got some new packing for the silencer today so cleaned up the core in preparation for re-wrapping it and found that it appears to be oddly flattened. It almost looks like it's been bent intentionally, and no idea how it could happen accidentally. So think I need to to round it back out but thought I'd check with you guys first to in case it's supposed to be like this. Seems like it should be round all the way end to end but maybe it's done as  some kind of performance improvement or something though I don't know how that could help. Heh, but then again, I don't know much. this is on a 77 IT 175 .Couple pics to show what I'm talking about.
Last edit: 25 Jun 2021 11:16 by Jack.
25 Jun 2021 11:10 #1

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Replied by Jack on topic Silencer core

I left it in it's flattened condition and re-wrapped and installed it back on the bike. Was hoping fresh packing might quiet it down a bit but didn't make any difference at all that I can tell. Don't guess there's any way to quiet the little beast down is there?

If anyone knows if it's supposed to be round or flattened let me know. I searched high and low for a pic of it and can't find anything other than the parts list drawings which you can't tell much from. 
25 Jun 2021 13:19 #2

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Replied by DT400FRANK on topic Silencer core

To me I think it should be round but I'm pretty sure that it being flat on one side wont hurt performance.   You could possibly find a pipe with the right diameter and bevel the end and drive the pipe through the baffle and tap around it to remove the creases and relax the metal but you may wind up damaging the tube if not careful 
25 Jun 2021 13:56 #3

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Replied by RT325 on topic Silencer core

If its still over-noisy has someone removed the spark arrestor deeper in the tail muffler. Not sure what to think with that baffle problem. Hard to imagine it happening without human input.
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26 Jun 2021 18:20 #4

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Replied by Jack on topic Silencer core

Thanks RT, I didn't even know there was anything up ahead of the baffle. I'll shine a light up in there tomorrow and see what's there and let you know. Parts lists don't show anything else in there other than the baffle I'm working with.
I agree with you that the mishaped baffle almost had to be done purposely by someone but haven't got a clue why they'd do that. Only possible reason I could think of was some kind of performance mod but not sure how that could make any difference. I think while I have it back out tomorrow I'll round it back out best I can and see if it runs any differently. Runs great just like it is but just curious if it'll make any difference.
26 Jun 2021 19:21 #5

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Replied by MarkT on topic Silencer core

1977 IT was a race bike and the AMA noise standard for off road was fairly high back then.  90+ dBa?   They aren't a super-quiet model. 

Spark arrestor should be the "Krizmann" type...  sort of looks like a jet engine turbine.
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26 Jun 2021 20:35 #6

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Replied by RT325 on topic Silencer core

 Yes if its an original muffler if ya look way down in it'll have a spiral vane looking thingy. If you can see straight through into the pipe that attaches it to the main exhaust then i guess its been removed. Found a relevant pic of a similar yamaha one i think.
Last edit: 26 Jun 2021 20:45 by RT325.
26 Jun 2021 20:42 #7

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Replied by Pete-RT1 on topic Silencer core

Just had a quick look on the CMSNL website and it looks to me as though the flat sides are original.
 
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27 Jun 2021 05:24 #8

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Replied by DT400FRANK on topic Silencer core

O my what's the theory or the function of this flatness. 
IM BAFFLED
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27 Jun 2021 06:44 #9

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Replied by Gr8uncleal on topic Silencer core

 
27 Jun 2021 07:37 #10

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