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Discussion Starter #1
OK, I've got the muffler off, and I'm looking at that perforated plate, and wondering ... if I drill a few holes in it to reduce the vibration problem etc, am I doing something I'll regret later? Will it be too noisy (remember, I'm an old fart and quite happy with quietness, although I wouldn't actually mind a slight increase in burbly type sounds from the muffler).

Can someone make some re-assuring comments? In the next few hours before it gets dark? It's 230pm here right now, Saturday arvo.

Scott
 

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Scott- The level of noise that is acceptable to you is subjective. Andy thought the Micron straight thru was too loud and sold it. But I like my Kerker straight thru. I was idling next to a Harley with straight pipes and couldn't even hear my engine one time. I had to look at the tach to start out. I personally didn't even think the ZR was that loud when I had no muffler on it (in between muffler changes). But I used to ride 2-stroke dirt bikes, so it's all relative.

If I were you, I would just let the moths out of the billfold and go buy an aftermarket muffler. If it were too loud for you, sell it through this forum and put the original back on. I don't like messing up my OEM stuff. BUt that's just my opinion...

kelly
 

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Discussion Starter #3
Hmmm - makes sense Kelly ... except an aftermarket muffler is around $Aus500-600 and the whole bike only cost $Aus9,000 on the road. And I've already spent $Aus500 on a Corbin (which, admittedly, was well worth it) and another $Aus150 on an F-15 shield.

And to sell on this forum would be a weeny bit difficult .. I think there's only about 50 Zr-7 riders (if that) in the whole of Australia (about 6 of them are on this forum). :(

So here's what I'm going to do. I'm going to drill just six 3/8 inch holes in the baffle and see what it does. If I like what I see (hear) then I'll drill some more.

I'll let you know how it goes. Wish me luck. :)
 

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Dirty Harry.... Moderator
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Bite the bullet Scott. Jarel says "Muzzy" and Tom says "Yoshimura"... others have said Micron is too loud, and others say blah blah. The Yoshi is mellow at low RPM, but absolutely wakes you up at 6,000 and upwards. My original can sets upstairs in case I want to sell the bike or should I bang the Yoshi in a fall. Tom

Poking holes in original equipment has always bothered me anyway, it's just me I guess!
 

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Try the can mod first. I think the mod is fairly easy and I like to new sound. It is not too loud for me.

Tips for the can mod:
1. Buy a 3/8" x 18" steel rod and sharpen one end.
2. Punch holes on the baffle with the sharpen steel rod.
3. Punch holes in a circle so that a large portion of the baffle can be removed.
4. Find a way to stabilize the can in a vise without damage. I used wood blocks and towels.
 

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Discussion Starter #6
Did it !

Drilled nine 3/8 inch holes in the baffle (quite simple really, must be easier than bashing it with anything - just need a longish drill bit).

By my reckoning that's equivalent to a 1 inch hole almost exactly.

Seems to have a slightly lower rumble at idle (when starting up) - nothing to annoy the neighbours and not really detectable unless you know what you are looking for.

As to more freely spinning at revs over 5,000 ... I spend so little time there anyway :( that I'm probably imagining it, but it does seem to run more freely.

I'll leave it as it is for a while until I can get some speed on a country road, and see what difference it makes to the vibration (again, this seems to be a little better but I don't think I can really tell reliably at this stage).

The main thing is, it doesn't seem to have buggered anything up, and should I ever sell (Heaven forbid !) the buyer won't know the difference.
 

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sorry i'm late! i completely removed that plate. i was scared too so i bought netlore's old muffler to experiment. it's not too much louder but definitely lower in tone. two of my riding buddies noticed it without me mentioning it. they like it better than the stock wisper. it seems to make more of a difference in lower revs as far as noise goes. notably louder but nothing compared to an aftermarket, you can still hold a conversation with it running.

i noticed no difference in vibes either way.

i think your stepwise process is a good bet.

scott :)
 

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Wheelie for Safety
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I just don't get it!

Vibrations are due to the harmonic inbalances all engines have. The faster you rev the engine the more it vibrates.

In my opinion, drilling the muffler or adding an after market slip-on will only add noise.

Andy
 

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Jarel is absolutely right - the vibes on the ZR-7 at 5,000 rpm are definitely affected by the can. Drilling the 2" hole in the perforated plate in my can achieved the following:

1. noticeably reduced vibes at 5000 rpm - nice
2. slightly deeper exhaust note at low revs - nice

I guess, Andy, that we should regard the pipe as a major component of the engine and vibes created there are transmitted though the frame and bars.

But what do I know? Heh heh heh.;)

Malc
 

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Mr. Clean
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Any photos??

Does anyone have any pictures of their stock cans being modified? I'm not sure if I should drill holes or just reomove the plate completely?! I'm happy with the bike's performance, it's just a little too quiet! :) Thanks!!
 

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Don't expect much doing this mod. I did it (cut away the 1st plate) maybe a 2-3 db higher not very noticable. i want with the micron it is loud but deeper tone the a d&d. :D
 

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Discussion Starter #14
Having had a nice long ride yesterday (Sunday), I'm happy with the result of my nine holes. Not a noticeable increase in noise, so
I'm going to add another 4 holes (taking it to the equivalent of around 1.5 square inches in total) and see (hear) what happens.

And, yes, I'll take some pictures. :)

But I'm bearing in mind the comment of a colleague who is a very experienced rider ... he said that all four-in-line engines have a vibration issue, in his opinion. I have no idea why.
 

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i did this mod friday afternoon. i only had a long phillips screwdriver so i lined it up with a hole in the baffle and rammed the end of the screwdriver into the wall. by doing this a number of times i was able to divide the baffle into four segments and then bend them back into the can. it was definitely primitive craftsmanship but that's the best i could do being a college student with no tools.

after two long rides satruday and sunday here is what i noticed:

there is a noticeable reduction in vibrations, and it also revs nicely on the upper end of the range. i barely noticed any difference in sound. i wouldnt recommend this mod for someone looking to make the bike louder but it definitely smooths things out and makes it run better. well worth the effort.
 

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yes, the whole exhaust system is part of the engine/vibe equation. at some certain flow rate it will possibly resonate. seems to be 5 k for most folks with a stock can.

if i can get my digicam hooked up i'll post some pics of an unmodified can to geive everyone a better idea of what's going on.

edward, don't expect huge noise or huge performance gains from this. it will sound a bit deeper and a bit lower in tone but there won't be any shrill rasp or HP gain. if that's what you're after then go with an aftermarket pipe.

scott :)
 

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Can..

OK....I'm in...! I'll modify the can as soon as some of you guys can post some pics....I must have an old 12" drill bit around....Used once to drill a long hole in a brick wall to run the DSS feed cable.

Also will like to take the can to a muffler shop (Midas..?) and see if they can drill the holes or make the can straight trough....If they can offer a cheap quote.

Ride Safe....!
 
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