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Old 04-23-2013, 03:46 AM   #21
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Quote:
Originally Posted by supercooper View Post
i would think that the bent rod, would shorten the upward stroke, even if only a small amount... when the spark went off, being that the piston wasnt where it was SUPPOSED to be, it would almost act like pre-detonation, slamming the piston down against the continual rotating mass, causing the knock against the crank.... even the smallest inconsistency can sound bigger than it is.

OR the slight bend put lateral torque on the piston, and it slanted in the cylinder, knocking off the cylinder walls... BUT, you said theres no wall damage.

im leaning more towards the first possibility
No, you can't alter the angular position of TDC & BDC by bending the rod -- those are fixed by the throws on the crank. The piston's linear axis of movement is constrained by the cylinder, so a bent rod basically acts like a shorter and fatter rod. The rod can hit the cylinder wall or the piston skirt can hit the crank at the bottom of the stroke.
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Old 04-23-2013, 07:19 PM   #22
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Here are a few more pics from teardown:





Cylinder 4
Attached Thumbnails
Please help identify this sound from my motor.-imag1086_zps07354d57.jpg   Please help identify this sound from my motor.-imagejpeg_2_2_zps9441c72d.jpg   Please help identify this sound from my motor.-imagejpeg_2_3_zps7739ee5c.jpg   Please help identify this sound from my motor.-imag1083_zps05c821fc.jpg  
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Old 04-24-2013, 06:40 PM   #23
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Quote:
Originally Posted by codrus View Post
No, you can't alter the angular position of TDC & BDC by bending the rod -- those are fixed by the throws on the crank. The piston's linear axis of movement is constrained by the cylinder, so a bent rod basically acts like a shorter and fatter rod. The rod can hit the cylinder wall or the piston skirt can hit the crank at the bottom of the stroke.
so, being that the bent rod acts like a shorter fatter rod, then when the piston is at its highest position in the cylinder, its still lower than if the rod werent bent, right?

so, would this JUST make a bigger space for combustion to occur, but still combusting when the CRANK is TDC?

could that create any kind of noise? because it doesnt look the the rod was bent radically enough for the piston skirt to knock on the rotating crank.

sorry, im just digging to find stuff out... its not easy to do, not having the engine in front of me, im just really curious where the knock could be coming from, so im running all kinds of possibilities through my head. lol
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Old 04-24-2013, 06:43 PM   #24
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could the bent rod have torqued the metal in some way down to the base, making a loose fit on the bearing, creating a larger clearance, and therefore a knock against the crank???
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Old 04-24-2013, 07:19 PM   #25
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You got a pm Kinavo. I want those rods.
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Old 04-24-2013, 07:32 PM   #26
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Oh hai, any new updates on that lamp?

As far as the rod goes, i'm guesssing it could make that sound since the weight difference to the one side could theoretically slap the cylinder at the wall. I'm guessing it also twisted sideways so it was harder to turn. At the very minimum ensure you get the walls honed and checked for roundness.
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Old 04-25-2013, 01:01 AM   #27
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Quote:
Originally Posted by triple88a View Post
Oh hai, any new updates on that lamp?

As far as the rod goes, i'm guesssing it could make that sound since the weight difference to the one side could theoretically slap the cylinder at the wall. I'm guessing it also twisted sideways so it was harder to turn. At the very minimum ensure you get the walls honed and checked for roundness.
Yeah, with a twisted and bent rod, plus missing chunks of piston, there's any number of reasons why that motor would make noise.

Personally I'm not sure I'd reuse any part of that bottom end.

--Ian
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Old 04-25-2013, 11:40 AM   #28
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I dont think there are missing pieces of the piston. It looks intact but I will double check. Nevertheless, I will have the cylinder rehoned and checked for roundness. I will have the crank checked and will replace the piston. Forged rods are already en route. All Rings and bearings will be replaced as well.

I appreciate the advice guys.

Regarding the hypothesis of the sound coming from piston slap, would the noise be as consistent or would it be more random?
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Old 04-25-2013, 12:38 PM   #29
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Quote:
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I dont think there are missing pieces of the piston. It looks intact but I will double check.
Your picture of cylinder #4 has what looks like a missing chunk at about 4 o'clock. Is that just oil or something?

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Old 04-25-2013, 03:23 PM   #30
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Quote:
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Regarding the hypothesis of the sound coming from piston slap, would the noise be as consistent or would it be more random?
My experience has been mostly consistent.
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Old 04-26-2013, 09:35 AM   #31
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Quote:
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My experience has been mostly consistent.

Interesting.


What you thought was a missing piece was in fact a carbon flake pushing to the side making it look like a hole.
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Old 04-26-2013, 06:11 PM   #32
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This part of the piston touches the crankshaft.
Please help identify this sound from my motor.-kolv.jpg


If you inspect your crankshaft you probably find marks on the "counter weights" dunno what you call it (I'm from non-English speaking country)

that is whats making the noise. My engi made the same noise when i bent my rods.
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Old 04-28-2013, 07:37 PM   #33
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Quote:
Originally Posted by myrando View Post
This part of the piston touches the crankshaft.
Attachment 74931


If you inspect your crankshaft you probably find marks on the "counter weights" dunno what you call it (I'm from non-English speaking country)

that is whats making the noise. My engi made the same noise when i bent my rods.
You are correct sir.





Here is a pic of the bearings on that rod. Is that normal wear? It doesnt look good to me.
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Please help identify this sound from my motor.-imag1097_zpsb878e1af.jpg   Please help identify this sound from my motor.-imag1098_zps91b27f2b.jpg   Please help identify this sound from my motor.-imag1099_zps4f08099b.jpg  
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Old 05-25-2013, 09:12 PM   #34
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Wow, it's a scary thought that a rod can bend on stock or sub 200 bhp.

Might be best to replace the bearings, don't know if that's normal or not.
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