Engine Noise Concerns
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Engine Noise Concerns
I know its difficult to diagnose over a forum but here it goes...
Today I noticed in gears 1,2 and 3 while at high rpm's, I hear a slight hissing sound kick in as though the carb opens all the way up. I normally don't get it up in high rpm's but it happened while getting out of a traffic jam...had to make a fast exit off to the shoulder to
avoid a wreck and throttled it pretty high.
Performance appears to be the same and the plugs looked normal. I changed them out anyway and still hear the hiss sound.
When I got home I let the bike idle while on the stand and got close to the lower case below the heads. I didn't hear any knocking or grinding sound but I do hear a type of rotary sound. Either that's new or I just never heard it before, maybe my ears are just playing tricks on me? But I do know for a fact the hissing sound is new.
Ideas?
Today I noticed in gears 1,2 and 3 while at high rpm's, I hear a slight hissing sound kick in as though the carb opens all the way up. I normally don't get it up in high rpm's but it happened while getting out of a traffic jam...had to make a fast exit off to the shoulder to
avoid a wreck and throttled it pretty high.
Performance appears to be the same and the plugs looked normal. I changed them out anyway and still hear the hiss sound.
When I got home I let the bike idle while on the stand and got close to the lower case below the heads. I didn't hear any knocking or grinding sound but I do hear a type of rotary sound. Either that's new or I just never heard it before, maybe my ears are just playing tricks on me? But I do know for a fact the hissing sound is new.
Ideas?
Outstanding HDF Member
Joined: Aug 2007
Posts: 2,225
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From: fegfsg
airleak, check the seal from the AC to the carb body, or carb to manifold.
You have air rushing into OR out of a small space at a high speed, thats the hissing noise.
and the speed or RPM doesnt matter so much, they just happen to be the frequency at which the airleak becomes obvious to your ears, its still there all the time though. Like how a whistle only works if you blow through it fast enough.
hopefully you just need to tighten a loose bolt or replace a worn gasket. no big deal. update on what you find what you do some poking around.
You have air rushing into OR out of a small space at a high speed, thats the hissing noise.
and the speed or RPM doesnt matter so much, they just happen to be the frequency at which the airleak becomes obvious to your ears, its still there all the time though. Like how a whistle only works if you blow through it fast enough.
hopefully you just need to tighten a loose bolt or replace a worn gasket. no big deal. update on what you find what you do some poking around.
Road Warrior
Joined: Jan 2008
Posts: 1,387
Likes: 1
From: Saint George, Utah
While it is definitely a good idea to check what Joseph had to say, my guess is, since there was no change in performance and you don't get up in the rpms that much you're just not used to the sounds. As far as the rotary sound your hearing, it's just the valvetrain doin it's thang, sporty's are a very loud motor.
Outstanding HDF Member
Joined: Aug 2007
Posts: 2,225
Likes: 4
From: fegfsg
While it is definitely a good idea to check what Joseph had to say, my guess is, since there was no change in performance and you don't get up in the rpms that much you're just not used to the sounds. As far as the rotary sound your hearing, it's just the valvetrain doin it's thang, sporty's are a very loud motor.
on my ducati though.. wow.. LOUD swoosh of air from the huge airbox that is directly under the gas tank. its cool when all the harmonics mix at the right freguencies and it turns into a nice hum, a very musical tone.
Stellar HDF Member
Joined: Dec 2006
Posts: 2,906
Likes: 11
From: Grottoes Va.
Normal for an evo, sportster or otherwise. All you heard was the motor sucking air. The rest is just the internals doing what they do. If there was an air leak, it would pop and generally run like crap.
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