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Old 03-14-2010, 05:42 PM   #16
Max Headroom
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Quote:
Originally Posted by El Hombre
I've read about using a 3/4" hole saw mounted on an 18" bit extension and drilling the baffle. Now that I can see what's exactly in there, I might not do it. That would bypass almost all of the baffles.

It's supposedly only a little louder, but from you photo, I don't think so.

Anybody try it? Too noisy?
IIRC, that was in an article about hotting up airheads printed in the early '80s, along with a bunch of other performance tips. I'd been reminded of that tip when I was looking at the pics of the disected muffler earlier too.

I'm quite reluctant to try that on my S/S Keihans, but am interested in feedback from anyone who has . . .
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Old 03-14-2010, 05:45 PM   #17
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I did the hole saw trick a lot "back in the day". It does seem to offer a bit more power, and since Udo Gietl suggested it to me...It's not a lot louder, really, just a little throatier.

I backed away from doing it when an older muffler started to come apart on me. That, and most of the guys who wanted fast bikes had moved on.
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Old 03-15-2010, 05:43 AM   #18
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Muffler gas backpressure?

I've just installed a set of Pea-shooters from Epco and had the header's ceramic coated.a month ago.

I'm experiencing .. low torque starting out and mid-range.

Once it's going ..it's like a jet.

Do I need to jet up or down? I need to get more air to the air box
What is the best way to do this. I'm hoping to have this figured on on
Tech day on Saturday
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Old 03-15-2010, 10:32 AM   #19
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i Really like those pea shooters. These are the same set you got.
Off of Ebay, "seconds"??
I think they were a steal!
Robert
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Old 03-15-2010, 10:34 AM   #20
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Here's a better angle
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Old 03-15-2010, 11:11 AM   #21
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exactly

couldn't resist....... I even bid on another set.. but got beaten
out by some guy in California.
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Old 03-15-2010, 03:00 PM   #22
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Interesting. Looks kinda lilke a cutaway of a Bose speaker. Exhaust 'tuning' is a bit of a black art, and the math is beyond me.

I do know that for each spark of the plug, there are two pressure waves exiting. One is the expanding gas, and the other is pure sound pressure, both of which move at two distinct speeds. Both of which utilize the available 'space' in different manners.
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Old 03-15-2010, 05:39 PM   #23
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Quote:
Originally Posted by rufusswan
...there are two pressure waves exiting.
Don't forget the waves reflected from the end of the system returning as well!
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Old 03-15-2010, 06:50 PM   #24
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I've been looking at cutaways of mufflers wherever I can find them.

I cannot quite tell the shape of the exhaust path from the front to the back. Is that a simple round tube with another sheet of steel behind it or is it a crecent-shaped tube?

THANKS for the pic.
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Old 03-16-2010, 07:45 AM   #25
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Snowbum suggests drilling 4 holes in the flat portion right at the rear adjacent to the outlet.

Looking at the slice that would appear to give some gas a straightish path out.

Probably wouldnt free as much gas as a 1/2 inch hole in the main baffle, but it is easier to reverse if it dont work out as planned.
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Old 03-16-2010, 04:11 PM   #26
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Was the muffler bearing already gone when you cut it open?
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Old 03-16-2010, 08:37 PM   #27
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Quote:
Originally Posted by JimX
Was the muffler bearing already gone when you cut it open?
Yeah, they're the first thing to rust out on these models.
The older bikes had a problem with worn phinifler pins and piston pull-back springs weakening, but these later bikes only suffered from rotting muffler bearings.
Go-figure.
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Old 03-16-2010, 08:53 PM   #28
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Quote:
Originally Posted by wirewrkr
Yeah, they're the first thing to rust out on these models.
The older bikes had a problem with worn phinifler pins and piston pull-back springs weakening, but these later bikes only suffered from rotting muffler bearings.
Go-figure.
RVV
I just hate seeing part names being used incorrectly It's kannidling pins and piston return springs. A weak piston return spring can lead to many hard-to-diagnose problems, including glowing generator warning lights at engine speeds above 13,000 RPM. A green bulb can improve the symptom, but does not fix the problem.
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Old 03-16-2010, 10:54 PM   #29
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Quote:
Originally Posted by bmwrench
I just hate seeing part names being used incorrectly It's kannidling pins and piston return springs. A weak piston return spring can lead to many hard-to-diagnose problems, including glowing generator warning lights at engine speeds above 13,000 RPM. A green bulb can improve the symptom, but does not fix the problem.
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Old 03-17-2010, 12:17 PM   #30
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Quote:
Originally Posted by Beemerboff
Snowbum suggests drilling 4 holes in the flat portion right at the rear adjacent to the outlet.
My first Beemer was an R60/6 that had this modification. It definitely had a more authoritative sound than other airhead bikes I'd ride with.
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