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Discussion Starter · #1 ·
On my Twin cam I've just had my heads ported & polished, and compression increased to ~10:1 (hopefully). the jugs are 95", and the weird thing is that in comparison to the bike with 95" at stock compression the bike now seems *louder*, although the pipes are the same. I listened as close as I could and can't hear or feel an exhaust leak, but have any of you noticed that the increased compression changes the *sound* the bike makes?
 

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Some Guy said:
On my Twin cam I've just had my heads ported & polished, and compression increased to ~10:1 (hopefully). the jugs are 95", and the weird thing is that in comparison to the bike with 95" at stock compression the bike now seems *louder*, although the pipes are the same. I listened as close as I could and can't hear or feel an exhaust leak, but have any of you noticed that the increased compression changes the *sound* the bike makes?
What, WHAT, a little louder please, I can't hear you! :Banadance
 

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IronButt
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It is really a great sound . Try 124 inch and 12.5 .1 sounds like a stock car, very staceto ( spelling?? ) pitch to hit. Not a good idea to wack the throttle in the garage unless you like having your ear drum slammed shut!!!
 

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HDWRENCH said:
It is really a great sound . Try 124 inch and 12.5 .1 sounds like a stock car, very staceto ( spelling?? ) pitch to hit. Not a good idea to wack the throttle in the garage unless you like having your ear drum slammed shut!!!

Hi Mr. Wrench!

I wonder what sort of fuel you would run with 12.5:1 compression?
 

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IronButt
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Well being that my dynamic is at at (near) 10.1 I can get away with 91 if temp is cool but in the heat 115 *f I do have to add a bit of FAST GAS I buy a drum of 116 and split it about 30%-50%. Heck with prices like we had here ;last summer race fuel is less per gallon than pump fuel. LOL
 

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HDWRENCH said:
Well being that my dynamic is at at (near) 10.1 I can get away with 91 if temp is cool but in the heat 115 *f I do have to add a bit of FAST GAS I buy a drum of 116 and split it about 30%-50%. Heck with prices like we had here ;last summer race fuel is less per gallon than pump fuel. LOL[/QUOTE

VP Motorsport 103, almost like haveing NOS on the bike.
 

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Same thing happened to me when I put 211's & SE perf heads on. I changed nothing else, and the exhaust note is louder & crisper. Oh so sweet !!
 

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Definiitly....changing compression changes sound

That is a fact.

Thats why when we tune our bikes its like tuning a musical instrument. I happen to be partial to the exahust note of a low compression engine. And i suspect so is harly because all their stock bikes are low compression.

As you increase the cr the exhaust note becomes higher frequency and louder.

And when you think about it that is part of the 95, 98 and 103 question.

You can get the same torque with all three displacements but you have to increase the cr to achieve it for the lower displacement motors.

So if you want more torque and a lower compression exhaust note you need to go with the higher displacement.
 

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Discussion Starter · #15 ·
A couple of more notes on my changes:

Decided to try an HB125 chain tensioner, and it is *great*! There is no "slap" or clunk with any shifts, it is a big improvement.

Gear driven cams do make a constant whirr that you can hear, but OTOH, with them installed I can't hear the whine of the fuel pump anymore, so that's overall a plus.

Finally, and most importantly, before I got the bike origianlly I had the dealer put in a 95" kit, and there was always what sounded like a lifter clicking in the front cylinder, which the dealer said was normal for the twin cam. With roller rockers & adj. pushrods & Jim's lifters, the noise is gone! Moral of the story, if there's an abnormal sound, it's not normal.
 

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Discussion Starter · #17 ·
Probably, but before installing them you'd have to admit
there was a problem with the stock ones that needed correcting...
 

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Some Guy said:
On my Twin cam I've just had my heads ported & polished, and compression increased to ~10:1 (hopefully). the jugs are 95", and the weird thing is that in comparison to the bike with 95" at stock compression the bike now seems *louder*, although the pipes are the same. I listened as close as I could and can't hear or feel an exhaust leak, but have any of you noticed that the increased compression changes the *sound* the bike makes?
Huge difference...
 
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