ScaredyCat
Expert Class
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posted July 26, 2003 03:43 AM
Dangerous exhausts?
OK I chose the title to get your attention, sorry. But you might be interested anyway, read on........
If I fit an aftermarket exhaust to my 12, or even remove it altogether (for argument's sake only), will the bike run so lean at any point in the rev band to cause damage to the engine? I can't imagine that it would, but I'd be interested in anecdotes. I would like a fruity sounding exhaust, but don't want to fuck up valves.
Before you start going on about the benefits of a Power Commander and how great it is think abou tthis:
1) Will I fuck my engine mixture-wise or otherwise by fitting a free-breathing (and better sounding) zorst?
2) Is the stock Fuel Injection set up assuming a certain exhaust (backpressure pulse) characteristic?
Doug, I'd appreciate your honest input on this as from the posts I've seen you are well informed on technicalities
like this.
Scaredy
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Hells Dark Lord
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living life, and loving it.
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posted July 26, 2003 04:57 AM
cant speak on a 4 stroke motor, but on my 2 stroke dirt bike, I lost the header bolts and had to ride it home with no exhaust attached...it scorched the rings on it, and I had to bebuild the top end. That was on an OLD CB250 Montesa....Anyone remeber those? like I said it may be different on a 4 stroke....Jim
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dougmeyer
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posted July 26, 2003 08:07 AM
Generally speaking you wouldn't hurt anything by not changing fuel with any "normally available" aftermarket exhaust" but you certainly will have some driveability problems, idiosyncracies, or "glitches".
If by "removing it" you mean literally just that- running the exhaust out of the ports to the open air, yes you would definitely hurt the exhaust valves, make the bike unrideable and probably burn it to the ground. If you want to fit some kind of "zoomies" or short straight pipes, it would still be unrideable, loose a lot of power, but you wouldn't burn it up. But hey
if "fruity" is where you're at, it's a free country.........
Doug
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dougmeyer
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posted July 26, 2003 08:11 AM
Very tactfully put, Huh, guys.....?
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12RPilot
Pro
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posted July 26, 2003 10:06 AM
My Muzzy and Power Commander seem to work well. Even though a pipe alone may work well enough, I just feel more secure with a custom map. Oh yeah, very tactful indeed, Doug.
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nedragr
Zone Head
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posted July 26, 2003 10:58 AM
quote:
Very tactfully put, Huh, guys.....?
As they say "delitefully tacky"
P.S. You've got mail, not ZX12 related, but ZRX1200 ????'s
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worm~hole
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posted July 26, 2003 01:07 PM
quote:
But hey
if "fruity" is where you're at, it's a free country.........
Doug
...heh heh...Doug said "fruity" 
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swft
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posted July 26, 2003 04:57 PM
can you say wafer thin mint??
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Necro
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posted July 26, 2003 05:00 PM
swft, did fish & freek leave?
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tedg
Moderator
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posted July 26, 2003 08:12 PM
quote:
cant speak on a 4 stroke motor, but on my 2 stroke dirt bike, I lost the header bolts and had to ride it home with no exhaust attached...it scorched the rings on it, and I had to bebuild the top end. That was on an OLD CB250 Montesa....Anyone remeber those? like I said it may be different on a 4 stroke....Jim
Factory trained Rickman (Triumph owned) mechanic here, and they had Montesa motors in them, also worked at a Montesa dealer. A two stroke will be hurt almost instantly by not having an exhaust. There is considerable unburnt fuel coming out of a the exhaust and the cool fresh air will ignite and super heat the piston and usually sieze at the exhaust. Especially the cyls with exhaust bridges. KTM would include a drill bit in their pistons to drill a hole in the piston to lube the bridge.
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ScaredyCat
Expert Class
Posts: 201
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posted July 31, 2003 06:39 AM
Thanks for the info!,
And there was nothing dodgy about the "fruity sounding exhaust" - but I'm not going to make a big deal about that for fear of being labelled a latent faggot... :-)
Anyways, I take your comments and don't worry I'm not going to go and unbolt my headers just yet... hehehe (that was just a hypothetical question, honest).
BUT - how does the exhaust backpressure (pulses or whatever) affect the richness of the mixture, and give a lean mixture with less backpressure?
I'd have thought the incoming charge was a "new" mixture every stroke, assuming of course that the exhaust scavenging was perfect - or is that what makes the difference?
I can understand it for 2-strokes, where the scavenging's crap, but I thought a hi-compression 4-stroke would have been a bit more immune to such things.
I'm not saying anyone's wrong, just like to understand the thing a bit more.
Cheers!
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