Clanking / clanging noises at high rpm

TheWizzerd

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Bearing on the tensioner wheel was fine.

Just tore down the engine, short of pulling the jug off. Nothing obvious. There was some carbon build-up on the piston dome and on the combustion chamber of the head so I cleaned those up. Spark plug looks good.

The only weird thing was that there was a bunch of oil in the magneto area. Weird thing was the seal and area behind the magnet was completely clean. I have no idea how the oil got there, the whole compartment was damn near spotless except for the fact there was a few oz of oil sitting in the bottom of it. No idea. It wasn't being slung around by the magnet.
Thats most likely the seal. It can appear to be clean around it as the oil drains down and off around it to a thin film that can be essentially invisible.

And, if its really bad, could be part of the noise you hear. A few ounces would be considered bad if its been a relatively short time since you had the cover off. I had a main seal on a YZ125 go once and it sounded like a bad exhaust leak coming out the crank.
 

weefek

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Thats most likely the seal. It can appear to be clean around it as the oil drains down and off around it to a thin film that can be essentially invisible.

And, if its really bad, could be part of the noise you hear. A few ounces would be considered bad if its been a relatively short time since you had the cover off. I had a main seal on a YZ125 go once and it sounded like a bad exhaust leak coming out the crank.
Regardless whether the seal is bad or not, It doesn't relate to the issue of my noises / vibrations. I will eventually pull this engine apart and replace bearings / seals / etc.

I dont get how the seal could be weeping oil and not slingling it around.
 

Chainlube

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Regardless whether the seal is bad or not, It doesn't relate to the issue of my noises / vibrations. I will eventually pull this engine apart and replace bearings / seals / etc.

I dont get how the seal could be weeping oil and not slingling it around.
It's at the early stages of going out completely, a minute amount of combustion oil gets forced past the seal every time you run it. The oil accumulates around the edge of the seal while you're running, but once you shut it down gravity does what you see.
 

TheWizzerd

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Regardless whether the seal is bad or not, It doesn't relate to the issue of my noises / vibrations. I will eventually pull this engine apart and replace bearings / seals / etc.

I dont get how the seal could be weeping oil and not slingling it around.
It weeps 100% of the time its running no matter what. The amount it weeps depends on what condition its in.

They do not seal 100%.


Also, how do you know its not related to your noise? Noise can absolutely come from bad seals. Not saying it is... but, seems you don't really know at all what and where it could be coming from. No offense, but you do need to have some knowledge about how these things work on a bit more advanced level to do advanced troubleshooting. Several very legitimate possibilities have been offered here and you suggest they are not the problem while stating in the same message that you do not understand how it could be.
 

DieselTech

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Well... I have no idea what I did, but the problem is even worse now.

It's around 3500 rpm / 15mphish now. I'm beginning to think it might be an issue with the bicycle and not the engine... I swear it sounds exactly like as if I took the two bolts off the front motor mount and the engine was slapping the frame.

I also noticed this time that every time I hit a decent bump / pothole it makes the exact same noise... as if the engine was loose or something. It's not. I've taken a rubber mallet to everything on the damn bike (being gentle of course) and nothing is loose or rattling. This is driving me nuts now at this point.

EDIT: I've got over every nut and bolt on the entire bike twice over now just in case I was an idiot and missed something.
Bicycle Frame might have a crack in it somewhere. That can cause the scenario you are talking about.
 

weefek

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It weeps 100% of the time its running no matter what. The amount it weeps depends on what condition its in.

They do not seal 100%.


Also, how do you know its not related to your noise? Noise can absolutely come from bad seals. Not saying it is... but, seems you don't really know at all what and where it could be coming from. No offense, but you do need to have some knowledge about how these things work on a bit more advanced level to do advanced troubleshooting. Several very legitimate possibilities have been offered here and you suggest they are not the problem while stating in the same message that you do not understand how it could be.

No offense, but you seem to have a thing about going off on people for no reason whatsoever. A barely weeping seal has 100% no relation to noises that sound like ball bearings in the combustion chamber. I've been building engines / cars since I was 7 years old, I work on and build industrial machinery for a living. I know how seals work.

Anyways. For those of you who care (probably very few) it was as I predicted, not engine related whatsoever. Thankfully @DieselTech it wasn't a crack in my frame somewhere (that was my worst fear but I went over the frame looking even for hairline fractures/cracks and nothing).

Tightened the top nut on the headset without making sure it was seated properly. The headset had about 1/4 of play in it. That's how bad this friggen engine vibrates. Properly seated and tightened the headset and no more noise. Stupidness. I'm definitely pulling the crank out of my new engine and balancing it before I throw it on this bike. But I'll run it for now until she blows.
 

DieselTech

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No offense, but you seem to have a thing about going off on people for no reason whatsoever. A barely weeping seal has 100% no relation to noises that sound like ball bearings in the combustion chamber. I've been building engines / cars since I was 7 years old, I work on and build industrial machinery for a living. I know how seals work.

Anyways. For those of you who care (probably very few) it was as I predicted, not engine related whatsoever. Thankfully @DieselTech it wasn't a crack in my frame somewhere (that was my worst fear but I went over the frame looking even for hairline fractures/cracks and nothing).

Tightened the top nut on the headset without making sure it was seated properly. The headset had about 1/4 of play in it. That's how bad this friggen engine vibrates. Properly seated and tightened the headset and no more noise. Stupidness. I'm definitely pulling the crank out of my new engine and balancing it before I throw it on this bike. But I'll run it for now until she blows.
A little P.M. never hurts, preventative maintenance goes a long ways on these motor bikes. Lol that being said mine has ran soo good & long now my pedal chain had stretched & fell off the sprockets the other day. Bout killed me when it slipped off!!! Like the play NutCracker!! Bad deal. 😂🤣😂
 

TheWizzerd

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No offense, but you seem to have a thing about going off on people for no reason whatsoever. A barely weeping seal has 100% no relation to noises that sound like ball bearings in the combustion chamber. I've been building engines / cars since I was 7 years old, I work on and build industrial machinery for a living. I know how seals work.

Anyways. For those of you who care (probably very few) it was as I predicted, not engine related whatsoever. Thankfully @DieselTech it wasn't a crack in my frame somewhere (that was my worst fear but I went over the frame looking even for hairline fractures/cracks and nothing).

Tightened the top nut on the headset without making sure it was seated properly. The headset had about 1/4 of play in it. That's how bad this friggen engine vibrates. Properly seated and tightened the headset and no more noise. Stupidness. I'm definitely pulling the crank out of my new engine and balancing it before I throw it on this bike. But I'll run it for now until she blows.

:ROFLMAO:

I really am straining here trying to see how it is that could have came across as going off on you.

I never suggested a "weeping" seal would make enough noise to be audible. I did suggest a very bad one that would result in several ounces of oil in the cavity in short time may.

And yes, bad crank seals CAN and DO allow noise to escape, and it can sound very much like various other noises engines make. Each stroke, the crank case is pressurized (this is what pushes the fuel charge into the cylinder through the transfers)..... if the seal is quite bad, where do you suppose that pressure goes? Escaping, pressurized gasses out of a hole generally have noise associated with it (just like out your exhaust). This is why audio based tools such as stethoscopes, and ultrasonic leak detectors etc. are widely used for detecting such leaks.....even in these type of crank seals.

Do an experiment. Take the mag side seal out and start it up. It will run, just not ideally. Prove me wrong, or educate yourself.


I am glad you found your problem however.
 
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