96' FLSTF knocking noise engine
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Novice
Joined: Sep 2012
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From: Oslo, Norway
96' FLSTF knocking noise engine
Hello 
Got a bit of a problem with my lady's Fat Boy.
It has been more and more smokey exhaust the last two/three weeks,
and lately I've noticed smoke from the breather filter aswell. The oil level has also sunk since I checked 3 weeks ago.
Was driving a short distance yesterday, just enough to get the engine hot, and when I pulled into a gas station I could hear a low, unsteady knocking noise from the engine.
I got the bike home in the garage, and today I pulled out one of the spark plugs and used a inspection camera to look inside the front cylinder. I chose the front cylinder because it came more smoke from the exhaust pipe from the front cylinder.
No marks on the cylinder walls, I was afraid the piston was making the knocking noise.
So I put the spark plug back in, and fired it up. The engine was as quiet as a evo can be (when running), and the exhaust was almost smokeless.
But when the engine got hot, the smoke came back and the knocking noise followed up..
With a stethoscope I could point out the noise from not comming from the cylinders, but more like from the engine bottom, where the primary case ar mounted to the engine..
Any suggestions for what this could be?
The bike's a 96' FLSTF with high compression pistons and a Andrews cam.
Cheers
Mr.E
Got a bit of a problem with my lady's Fat Boy.
It has been more and more smokey exhaust the last two/three weeks,
and lately I've noticed smoke from the breather filter aswell. The oil level has also sunk since I checked 3 weeks ago.
Was driving a short distance yesterday, just enough to get the engine hot, and when I pulled into a gas station I could hear a low, unsteady knocking noise from the engine.
I got the bike home in the garage, and today I pulled out one of the spark plugs and used a inspection camera to look inside the front cylinder. I chose the front cylinder because it came more smoke from the exhaust pipe from the front cylinder.
No marks on the cylinder walls, I was afraid the piston was making the knocking noise.
So I put the spark plug back in, and fired it up. The engine was as quiet as a evo can be (when running), and the exhaust was almost smokeless.
But when the engine got hot, the smoke came back and the knocking noise followed up..
With a stethoscope I could point out the noise from not comming from the cylinders, but more like from the engine bottom, where the primary case ar mounted to the engine..
Any suggestions for what this could be?
The bike's a 96' FLSTF with high compression pistons and a Andrews cam.
Cheers
Mr.E
Thread Starter
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Novice
Joined: Sep 2012
Posts: 16
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From: Oslo, Norway
Thought of the lifters, and tried to listen to them with the stethoscope, but it seemed like the knocking came from the other side of the engine block.
As for the oil usage, I'm thinking of taking of the intake and check the inlet valve stem for oil. If the valve stem is clean, the only other possible explanation would be piston rings, right?
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,080
Likes: 2,154
From: Ohio
Noticable smoke from the exhaust is oil getting into the cylinder and more pressure into the crankcase breather system is compression going past the rings into the vent system, you've had a piston stick to the cylinder and cylinder scuffing because nothing else can cause more pressure into the crankcase and audible noise. A scuffed cylinder will also become louder when it heats up, going to need a compression test to confirm and give yourself a direction for repairs.
Thread Starter
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Novice
Joined: Sep 2012
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From: Oslo, Norway
Thanx mates Will do a compression test after work today. But if the problem is in the cylinder or with a piston, shouldn't I be able to hear the knocking directly on the cylinder with the stethoscope? The only knocking I can find comes apparently from the cranckcase.
Will do a compression test after work today. But if the problem is in the cylinder or with a piston, shouldn't I be able to hear the knocking directly on the cylinder with the stethoscope? The only knocking I can find comes apparently from the cranckcase.
Road Warrior
Joined: Nov 2008
Posts: 1,595
Likes: 8
From: Vancouver Island British Colombia Canada
Noises are a lil tricky to pin point at times. Compression test is your first step. Both plugs out, Throttle wide open for max air & do the same for both cylinders. If you have a score in the wall or a piston with a crack, your compression test will tell you! No more than 20 pounds difference between cylinders.
Keep us posted! Hatch.
Keep us posted! Hatch.
Thread Starter
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Novice
Joined: Sep 2012
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From: Oslo, Norway
Will keep you updated
Going to do a compression test first with cold engine, and then with hot engine just to be sure
Going to do a compression test first with cold engine, and then with hot engine just to be sure
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Thread Starter
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Novice
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From: Oslo, Norway
Here's the compression tests
Due to the poor markings of the pen in the test instrument, I've highlighted the results. The test to the right is the cold test, with cylinder 1 and 3 showing the front cylinder, and 2 and 4 showing the rear cylinder.
The test to the left is with warm engine, knocking noise and smoke present.
Just got to know, can a high oil level in the reservoar tank produce smokey exhaust....? Measured the oil level with warm engine, and the oil level was way higher then I expected.. Like almost 0,5" over max marking
Due to the poor markings of the pen in the test instrument, I've highlighted the results. The test to the right is the cold test, with cylinder 1 and 3 showing the front cylinder, and 2 and 4 showing the rear cylinder.
The test to the left is with warm engine, knocking noise and smoke present.
Just got to know, can a high oil level in the reservoar tank produce smokey exhaust....? Measured the oil level with warm engine, and the oil level was way higher then I expected.. Like almost 0,5" over max marking
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Thread Starter
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Novice
Joined: Sep 2012
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From: Oslo, Norway
Yep, it wasn't much difference on the cylinders there.
But here's a video I made this evening to give an ecample of how the knocking sound sounds like. You can hear the sound sometimes as a single knock:
http://img24.imageshack.us/img24/488...nboqgfitye.mp4
But here's a video I made this evening to give an ecample of how the knocking sound sounds like. You can hear the sound sometimes as a single knock:
http://img24.imageshack.us/img24/488...nboqgfitye.mp4