Clanking / clanging noises at high rpm

FrizzleFried

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Good idea. I haven't done this. I will do this tomorrow. It could maybe very well be chain related , but i'm pretty confident it's coming from the engine top or bottom end. I admit I could very well be wrong. I have a mechanics stethoscope i'll try that. I don't have any gosh darn fish.

The chain stay is pretty far rear-wards, this noise is coming from the engine area 100%.
I know my chain will hit my rear motor mount from time to time...

....could it be high RPM 4-stroking?
 

Chainlube

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Good idea. I haven't done this. I will do this tomorrow. It could maybe very well be chain related , but i'm pretty confident it's coming from the engine top or bottom end. I admit I could very well be wrong. I have a mechanics stethoscope i'll try that. I don't have any gosh darn fish.

The chain stay is pretty far rear-wards, this noise is coming from the engine area 100%.
Chains can echo around and sound like they're coming from the engine.
Its detonation or engine ping from over rpm range of ignition system. Or it could be piston kissing the cylinder head from heat expansion or excessive rpm.
It ran fine up til now, if he had a preignition situation it would have showed by now, because he said he had the head off a couple times and most likely cleaned any carbon off at that time.
 

weefek

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Chains can echo around and sound like they're coming from the engine.

It ran fine up til now, if he had a preignition situation it would have showed by now, because he said he had the head off a couple times and most likely cleaned any carbon off at that time.
Possibly chain noise, although I doubt it.

It still runs fine, even with the noise. I may just take the head off and check.

Im going to run it up to speed on a stand here shortly and use my mechanic stethoscope to see what I can find.
 

weefek

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Its detonation or engine ping from over rpm range of ignition system. Or it could be piston kissing the cylinder head from heat expansion or excessive rpm.
I thought the stock ignition systems could handle 7200ish rpm ? I suppose that's possible.

Definitely not the piston kissing the head, my squish gap is 2.7 mm.
 

weefek

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Well, running it on a stand is a no-go. 1) I have a spring style tensioner and the chain jumps around a lot without a load 2) the noise doesn't happen unless it's under load.

Once the bike cools down I'm going to start pulling stuff apart see what I can find.
 

Chainlube

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Well, running it on a stand is a no-go. 1) I have a spring style tensioner and the chain jumps around a lot without a load 2) the noise doesn't happen unless it's under load.

Once the bike cools down I'm going to start pulling stuff apart see what I can find.
Check the bearing on the tensioner wheel.
 

weefek

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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.
 

weefek

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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.
 
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