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Discussion Starter #1
JohnnyB,
I just put an unknown 4-1 system on my Seca 550 racebike. It is obnoxiously loud. The baffle is an endplate with a tube welded on it with no crossholes or sound deadening material in it. I would like to add some supertrapp disks to it. The baffle end plate is 3 1/2" diameter. Should I use 3" r 4" discs? I don't care if the 4" discs are a little bigger diameter since it is a race bike, but is the diameter of the mounting holes such that they will fit in the endplate, or would I have to make an adapteer plate? Or will the 3" disks flw enough tthat I don't need to worry about going to the 4"? How many plates do you think I might need?

Thanks,
Ken

AHRMA 412
Vintage racing - old guys on old bikes
 

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I'd say you want 4". Problem is, 3 1/2" end diameter might interfere with the bolt holes of the 4" disks...although I think they would just clear to the inside of 3 1/2".
I'd start with about 12 4" disks.
If I remember I'll measure the bolt circle on a 4" disks.
You'll need to weld on a mounting plate of some sort anyway.
JohnnyB
 

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Discussion Starter #3
Thanks Johnny,
It shouldn't be a problem to mount the 4" discs. I will leave the baffle in place and either make an adapter plate to fit the bolt pattern of the 4" or weld nuts to the baffle tho accept the 4" if the bolt pattern diameter is small enough.

I will order a couple of sets of plates today and see how it goes.

Ken

AHRMA 412
Vintage racing - old guys on old bikes
 

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Ken...I make the weld on plates seen here:

http://www.jrbranson.com/BikeParts/CDR-Parts.htm

If I have any in stock I'd be happy to sell you one :)

If I don't have any in stock...well, they are a pain to make and I don't have time now.

The holes have to be really really in the right place, and threaded really really straight. Even with my rotary table and tapping machine I have a reject now and then.
JohnnyB
 

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Discussion Starter #6
JohnnyB,
Looks good, let me check out how the 4" disks will mount up to the baffle end piece that is already in thre and if I need an adapter plate I will let you know. I don't want it to be extra work for anybody especially me. it looks like I might nt need it for a month or so.

Texy, I finally got back to the lower 48 last Tuesday. I e-bayed a bunch of suspension parts, brake parts and an exhaust. So, I have started to work on the Seca and I have an Ascot parts bike I need to pick up and see what I can do with it. It looks like I am not going to make any of the regular races this year but, Brainerd with CRA looks like it can happen in July. I haven't raced there since about 81. It is only 3 hrs from home so that is probably what I will do. I have to be back at work in AK on July 31.

Ken

AHRMA 412
Vintage racing - old guys on old bikes
 
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