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Old 3rd November 2008, 18:08   #1
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Arrow More thump from AVL engine

Well this comes from the HEART!
It really frustrates me no-end when I see (hear, rather) a fellow thumper on old CI bull, thumping his engine at no more than heartbeat pulse rate, chugging at a relaxed pace on the road.

Why does that frustrate me?
Becuase I have AVL engined TBird. Might look more classy (ofcourse debatable) than a CI Bull, but no match in thump.

The reasons?
Contrary to popular belief, its not the muffler. The muffler can only increase or decrease the sound levels. But it cannot create the thump.

The CI Bull gets is thump from heavy crank case, which allows the engine to rev low, and the low-end torque which is higher than AVL engine (at the same low RPM). Thus on AVL bikes you are compelled to keep the engine running at 2000 + RPM.
Whereas on CI bulls you can cruise comfortably in the 1000-2000 RPM range as well.

And THERE lies your thump range.
The glorious "DUG DUG DUG" rhythm.

So, my question here is - is there any way to make our AVLs run at that low RPM without the engine knocking and choking?
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Old 3rd November 2008, 20:10   #2
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increasing crank weight? I dont no whether avl also can achieve this!
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Old 3rd November 2008, 22:28   #3
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The DUG DUG your mentioning in because of the iron casting of the engine not the crank buddy. Every metal has different properties of absorbing sound and has the sound.
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Old 3rd November 2008, 22:36   #4
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Quote:
Originally Posted by alpha1 View Post
And THERE lies your thump range.
The glorious "DUG DUG DUG" rhythm.

So, my question here is - is there any way to make our AVLs run at that low RPM without the engine knocking and choking?
Alpha, that a million dollar question you are asking and I'm not sure if even Enfield knows the answer. I personally dont think it just one thing but a combination of several things that give that magical 'thump-a-thump-a-thump"

Unfortunately too many things have changed in the AVL engine including the combustion characteristics of the chamber and that I think is the primary reason. The clatter comes from the tappets if I am not mistaken.
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Old 3rd November 2008, 23:06   #5
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Get a Goldstar silencer. It'd give you a better sound track.
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Old 3rd November 2008, 23:23   #6
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Two options
1)Get a gold star

OR
2)Plonk a CI engine.
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Old 4th November 2008, 04:14   #7
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Quote:
Originally Posted by akshay4587 View Post
Two options
1)Get a gold star

OR
2)Plonk a CI engine.
Goldstar would again make the current sound louder nothing else, that dug dug could be acheived only by a Ci engine and that also a older engine not the new ones that come with the Electra
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Old 4th November 2008, 07:51   #8
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Quote:
Originally Posted by desideep View Post
Goldstar would again make the current sound louder nothing else, that dug dug could be acheived only by a Ci engine and that also a older engine not the new ones that come with the Electra
Gold star does provide meatier thump to the AVL's much better than stock exhausts
Although not anywhere near the so called DUG DUG of CI
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Old 4th November 2008, 09:01   #9
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Goldstar gives a loud noise , not sure whether you folks call it a thump!!
Plus adding a free flow exhaust adds to the pain of retuning the carb which else you'll hear that loud PHATAAK once you release the throttle since. So add a goldstar only if you are ready to reject ur bikes carb or you'll be damaging the head valves.
Try with the short bottle silencer(original RE) it might solve your purpose.
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Old 4th November 2008, 11:16   #10
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OK folks, lemme clarify:
I have experienced the stock TBrid muffler (the extremely long cigar shaped one)
The short old bull silencer
and currently the TBird sports Glodstar.

Thats how I came to the conclusion that all muffler does is to increase/decrease the intensity of the exhaust sound.

It cannot change the exhaust sound.


I agree the there are more things which attritbute to the change in sound, however, my reasoning is this:

The thump thump that you hear is nothing but the firing / combustion stroke. That gives you the engine RPM.

If you listen carefully and time - the thumps from old Bulls are like 2-3 per second.
That means (3)*4*60 RPM = 720.
thats the idling speed.

And the thump while the bike is running makes the figures 1000-1500 RPM.

Can the AVL run that low?
No.

Ofcourse even if I get the AVL to run that low - I might not match the old bullet thump, but atleast I would be closer

Last edited by alpha1 : 4th November 2008 at 11:17.
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Old 4th November 2008, 12:10   #11
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Hehe, in my opinion AVL can't be compared to CI and hence the thump. It is a different engine and as many said here the different setup makes a different exhaust note too. The issue is we try to match AVL with a CI and AVL and guys gets dissapointed. I have seen many. Consider AVL as AVL. It is a fast revving, lighter engined bike compared to CI and it has its advantages more.

I ride a CI 500. Even my bike doesn't have that classy thump of the old CI 350s. In my opinion the CI 500 has a different, mettallic thump than CI 350 deep bass thump. But I love this and enjoy her at fullest. I run a Goldie and the high revs harmonics is a music to me, especially when I leave the throttle after a revv .
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Old 4th November 2008, 12:13   #12
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PS: The clatter aspect of AVL is somehting I have never understood.
If anyone is there in Pune, just check my bike.

Its AVL, and it doesn't make any racket.

Surprisingly at my mechanic's place (thankfully, its just at the colony gates) I came across a Machismo 500 AVL. And what a metallic racket it made!

Thats when I heard the "racket associated to AVL engines"


But, the only noise I can hear on my bike is "clockwork" noise (the pleasant and mild kir kir of the rockers/pushrods/tappets/cam spindle).

Is that what the clatter is all about?
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