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It had what I believe to be aftermarket pattern repro CX 650E mufflers when I got it and I suspect the baffles had been tampered with (it was much louder than I like). I don't remember a sudden increase when I changed to the HD mufflers but that may be because I changed them during the summer restoration session (when you use it in winter some work is needed every year) and I tend to use the throttle carefully on wet/snowy winter roads. The next spring when the roads were clear & dry I noticed that I had to lean over the bars to keep the wheel down when accelerating hard from a stop into a break in traffic.
I'm pretty sure it worked better with the HD mufflers but I couldn't say how much of that was because the ones it came with weren't very good.
 

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When i worked at the local Air Force base they had RFI/EMI (i assume both) anechoic chambers that were lined with copper. With guitars that are having trouble with EMI they line the area where the pots & electrical connections are with copper, would this be a solution here also?
 

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Copper is non-magnetic so it won't have much if any effect on the magnetic fields.

They line guitar cavities with copper tape because it will block electrical interference. Aluminum based duct tape would work too but you can solder a ground wire to the copper stuff.

My background in audio says that anechoic (without echo) chambers are for studying the sounds produced by things (in my experience usually speakers). I guess any rf or em shielding would be there to prevent interference from affecting the instrumentation. We just made sure the equipment itself was shielded :rolleyes:
 

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I agree with you on the audio and anechoic chambers (i've been in an audio one and it is quite unsettling to say the least) but they always called that one at the base that and i wondered why?
 

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It seems they make anechoic chambers for testing other things that require a place with no echo at the frequencies they operate at too. The one at the air base is probably similar to this (I had to look that up because until you mentioned it I wasn't aware of anechoic chambers for anything except audio).
 

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Anechoic chamber question answered! Interesting link/wiki on it.
 

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Discussion Starter #247
I noticed while I was out just now that the hitting of birds at 60 kmh hasn't actually gone away..

Next step - add steel shielding for EMI ....

The bike is much better with the sportster mufflers fitted and I've just added the K+N filter from my 500C to the airbox.

There seemed little point before as the mufflers weren't allowing the bike to breathe anyway.
 

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cool - if that doesn't make a difference can you try the other timing curves - it coul just be a particular pulse width combination at certain revs is causing hunting with the timing - if so easily fixed,
but would be nice to resolve it.
Rayman
 

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These are 'export only' mufflers and have two large drill holes put through the centre.
Mark,

Did you mod the mufflers by drilling them out or did you just get them that way? Do you recommend drilling them out? What exactly was drilled and how large a drill, if you don't mind me asking?
 

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Discussion Starter #252
These were a pair of mufflers of unknown origin I had in the shed. I'd have got them with one of the parts stashes I've accumulated over the years.

They were already drilled when I started fiddling with them - two holes in each of about 15 mm - and overlapping. Quiet on small throttle openings, loud as hell on larger.

I have now jammed a washer up each one from the front now giving a single 13 mm hole and this is generally quieter. Before jamming the washer in I cut it around the periphery with a hacksaw to give it teeth to grip. The washers used are also dished suspension bushing washers.

Looking through where these mufflers were drilled it looks like they've drilled through 4 or 5 plates. I can't figure out the flow path through these mufflers as the rear half appears to be solid pipe internally.

Am considering putting washers in from the back now to try for quieter and perhaps then putting a bolt and nut through to both secure the washers further and cut more noise. This would I guess return them to close to original noise and flow. The one question is will that flow be enough?

These are {presumably} sportster mufflers but unknown whether from an 883 or 1200 {if the mufflers are in fact different}

Does anyone know the peak revs of these harley motors? If the pumping flow from the harley motor is high enough that should be OK for a CX, which while it has smaller cylinders to exhaust presumably spins {and therefor pumps} a lot faster. With a known peak rev, comparitive flow should be calculable.

On a different note I have just rebuilt every plug cap I have here - 7 sets in all. Some with, some without resisters.

Am now rebuilding a set of VB36s and about to start on another Euro set for Eric.
 

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From memory i thought it was 5500. I did a few interweb searches and it seems the 883 rev limiter was set at 6000 from what i saw. I doubt any stock harley revs to 9500, potatoes can't move that fast!!! :D
 

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Discussion Starter #254
Harley mufflers should be OK, though the CX flows a little more than the 883.

CX500 - 250 x 10,000 = 2500000

883 -441 x 5500 = 2425500

1200 - 600 x 5500 = 3300000

The numbers to me are meaningless in and of themselves but do show which is larger.

If there's a difference between 1200 and 883 mufflers the 1200s are the ones to have.

Of course, things are rarely actually that simple and relative compression ratios likely play a part. .... but this is good enough for my rule of thumb. ;)
 

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So you are just calculating the volume of air (approximately) moving through the engine at redline as a comparison.
 

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Discussion Starter #260
The best I have Murray.

One is 4 valve, the others 2.

There's degrees of cam duration and lift.

It gets much more complex I know.

But .... that's good enough for me.Taking it further is beyond my capabilities.

While a CX may outflow an 883 by more than the figures suggest I still doubt it can outflow a 1200.
 
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