Valve spring noise?
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Road Warrior
Joined: Nov 2005
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From: Mountain View, California
Valve spring noise?
If I place my engine under heavy load at lower RPMs - say 3,000 below - I consistently hear a noise that I have thought was knock, but I'm beginning to think might be more valve train related..
The sound is like what you might expect to hear what a large spring under tension is cut, that sort of twangy sound. It's not a classic sound of knock
When I had the engine built, I know the builder installed heavier springs that's really all I can remember about them.
Does this sound like a spring issue, or can knock make a sound like I described?
At higher RPMs when I crack the throttle I don't hear the noise, only when I'm in lower RPM ranges.
Thanks in advance for sharing your knowledge
The sound is like what you might expect to hear what a large spring under tension is cut, that sort of twangy sound. It's not a classic sound of knock
When I had the engine built, I know the builder installed heavier springs that's really all I can remember about them.
Does this sound like a spring issue, or can knock make a sound like I described?
At higher RPMs when I crack the throttle I don't hear the noise, only when I'm in lower RPM ranges.
Thanks in advance for sharing your knowledge
Last edited by Z; Aug 16, 2023 at 02:33 PM.
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Road Warrior
Joined: Nov 2005
Posts: 1,484
Likes: 82
From: Mountain View, California
@2500hdon37s Damn, I never thought about the compensator being the source of the noise.
Just to be sure though, the noise sounds like a spring under tension being cut - that twang sound - and it persists until I back out of the throttle (which I do instantly), and seems only to happen at lower RPMs (SUB 3000). You're saying this is a typical failing compensator sound?
Just to be sure though, the noise sounds like a spring under tension being cut - that twang sound - and it persists until I back out of the throttle (which I do instantly), and seems only to happen at lower RPMs (SUB 3000). You're saying this is a typical failing compensator sound?
Last edited by Z; Aug 16, 2023 at 04:08 PM.
HDF Community Team
Joined: Jun 2006
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From: san antonio
Harley's make lots of sounds but "twang" is a new one. OP says motor has been "built" but leaves out build details and whether or not the build was tuned. I would want to know those details before suggesting the source of the "twang". I will say that putting the motor under heavy load below 3000 rpms is not a good idea.
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Road Warrior
Joined: Nov 2005
Posts: 1,484
Likes: 82
From: Mountain View, California
Harley's make lots of sounds but "twang" is a new one. OP says motor has been "built" but leaves out build details and whether or not the build was tuned. I would want to know those details before suggesting the source of the "twang". I will say that putting the motor under heavy load below 3000 rpms is not a good idea.
Buold details are in my signature but I'm glad to reproduce them here:
S & S 100 inch 10.5:1 kit + 570 easy-start gear drive cams, ported heads with 0.060" over intake valves, Thunderheader 2-1 exhaust, Arlen Ness Big Sucker air filter, ThunderMax ECM.
When I say heavy load what I really mean is, If I'm rolling along in the 2000 to 3,000 RPM range, and I roll onto throttle more than slowly and carefully until I get through that range, I hear that sound. It's absolutely more pronounced when hot.. I don't know if that helps. The timing curve loaded into the bike it's from a similar biuild and obviously with the ThunderMax the air fuel mixture is automatically tuned (I installed O2 sensors in both of my pipes)
Last edited by Z; Aug 16, 2023 at 05:23 PM.
HDF Community Team
Joined: Jun 2006
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From: san antonio
My bad; I was responding to your first post and missed the build details in your second post.
Your description of the sound as a "twang" doesn't fit the noise generated by detonation but the conditions under which the noise presents indicate, to me anyway, that detonation may be a source of the noise. The fact that the noise presents more pronounced when hot and having to baby throttle to get through the 2K-3K range and the fact that the timing curve is from a "similar" build all point to detonation for me which would present like littel ball bearings bouncing around in the combustion chamber. I don't know anything about the TMax but from what I have read, tweaking timing to be compatible with the build requires manual inputs but, like I said, I know nothing about the TMax.
If I were in your situation, I would get the bike on a dyno for a proper tune focused on the timing curve.
Your description of the sound as a "twang" doesn't fit the noise generated by detonation but the conditions under which the noise presents indicate, to me anyway, that detonation may be a source of the noise. The fact that the noise presents more pronounced when hot and having to baby throttle to get through the 2K-3K range and the fact that the timing curve is from a "similar" build all point to detonation for me which would present like littel ball bearings bouncing around in the combustion chamber. I don't know anything about the TMax but from what I have read, tweaking timing to be compatible with the build requires manual inputs but, like I said, I know nothing about the TMax.
If I were in your situation, I would get the bike on a dyno for a proper tune focused on the timing curve.
Thread Starter
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Road Warrior
Joined: Nov 2005
Posts: 1,484
Likes: 82
From: Mountain View, California
My bad; I was responding to your first post and missed the build details in your second post.
Your description of the sound as a "twang" doesn't fit the noise generated by detonation but the conditions under which the noise presents indicate, to me anyway, that detonation may be a source of the noise. The fact that the noise presents more pronounced when hot and having to baby throttle to get through the 2K-3K range and the fact that the timing curve is from a "similar" build all point to detonation for me which would present like littel ball bearings bouncing around in the combustion chamber. I don't know anything about the TMax but from what I have read, tweaking timing to be compatible with the build requires manual inputs but, like I said, I know nothing about the TMax.
If I were in your situation, I would get the bike on a dyno for a proper tune focused on the timing curve.
Your description of the sound as a "twang" doesn't fit the noise generated by detonation but the conditions under which the noise presents indicate, to me anyway, that detonation may be a source of the noise. The fact that the noise presents more pronounced when hot and having to baby throttle to get through the 2K-3K range and the fact that the timing curve is from a "similar" build all point to detonation for me which would present like littel ball bearings bouncing around in the combustion chamber. I don't know anything about the TMax but from what I have read, tweaking timing to be compatible with the build requires manual inputs but, like I said, I know nothing about the TMax.
If I were in your situation, I would get the bike on a dyno for a proper tune focused on the timing curve.
I've had too many bad experiences with dyno time to want to throw any more cash in that direction.
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