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Sound File - what is making this sound?

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malmac
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Sound File - what is making this sound?

Post by malmac »

Well guys here is an audio puzzle.

There are two sound files.

1. 600cc /2 bike at idle. This bike has a new crank, pistons and carbs - to mention the major parts of the engine rebuild.
Bills_r60_@idle.mp3
(979.7 KiB) Downloaded 81 times
To me this engine is running fine.

2. 600cc /2 bike at idle. This bike has a new crank, 1st oversize cam followers, new timing gears, pistons and carbs - to mention the major parts of the engine rebuild. The engine case is stamped "-0" but I have had to fit "-5" timing gears to get the backlash within spec (measured at .015mm) backlash. Below is my set up for measuring the backlash.
MAL_5435.jpg
r69s_idle_nov1.mp3
(967.51 KiB) Downloaded 59 times
To me this engine does not sound happy.
The bike starts first or second kick, runs strongly, does not overheat and the sound does not get better or worse when hot.

Any insights would be most appreciated. Hopefully Vetch will have the time to give me his most sought after opinion.

Thank you in advance.

Mal
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Re: Sound File - what is making this sound?

Post by jwonder »

Sounds like valve tap, who did the heads?
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malmac
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Re: Sound File - what is making this sound?

Post by malmac »

jwonder wrote:
Sun Oct 30, 2022 10:48 pm
Sounds like valve tap, who did the heads?
James.

The heads have not been touched. The heads have been re torqued and valve clearance checked but What is valve tap? Please.

Mal
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Re: Sound File - what is making this sound?

Post by malmac »

So if I understand right. If the cam followers are sticking, then the valves stick open and the pistons tap them closed.

If that is the case then that is not a great plan, as much as Ducati had desmodromic valves, I know this was not the mechanism.

I will do a leakdown test and then check it out with the spanners.

Thanks for the feedback. Much appreciated.


Mal
mal - R69s
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Re: Sound File - what is making this sound?

Post by malmac »

I was concerned that maybe the cam followers(tappets) were too tight in their bores. I had fitted 2nd oversized tappets and honed the bores to size. Had I made adequate clearance was my question.
Today I pulled the pushrods one at a time and by inserting a small stainless steel filler wire careful up the pushrod tube I was able to insert the wire far enough into the oil feed hole in the tappet to activate the tappet in it's respective bore.
Each and every one was able to move freely. These would certainly not be sticking.

No sign of broken valve springs.

Mal
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Re: Sound File - what is making this sound?

Post by vechorik1373 »

This may be a silly question, but, when you had the push rods out, did you roll each one on a piece of glass, to check to see if they were absolutely straight? Once a push rod gets bend in it, (they are only strong when perfectly straight) it will continue to flex and bend. This will make an audible ticking nose.
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Re: Sound File - what is making this sound?

Post by malmac »

vechorik1373 wrote:
Tue Nov 01, 2022 1:30 pm
This may be a silly question, but, when you had the push rods out, did you roll each one on a piece of glass, to check to see if they were absolutely straight? Once a push rod gets bend in it, (they are only strong when perfectly straight) it will continue to flex and bend. This will make an audible ticking nose.
Vech, thank you for making this point.

I did not do the rolling test. I will follow up on this and check them out.

The sound that seems most disturbing to me is the sort of croaking sound which comes and goes - it is not apparent once the engine is above idle, but at idle it is quite noticeable - it makes the engine sound like a sort of pumping action is taking place.

The engine has new timing gears and also it has the new breather plate with the opened out breather holes - Is it possible that this may be where the sound is coming from?

Thank you for reading and responding.

Mal
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Re: Sound File - what is making this sound?

Post by schrader7032 »

A pumping or groaning sound could be the crankcase breather, or worse yet, air working past the rear main seal. If the internal engine pressures are building up, the air has to go somewhere. If the pressures are building, then it is likely ring blow-by which you could check as part of a leakdown test.
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Re: Sound File - what is making this sound?

Post by wa1nca »

I recall their was a post about breather noise after a new rear main seal was replaced (mostly at low rpm's)and was sort of normal but should go away after some time

If you removed the oil dipstick and the sound goes away it most likely because of the new rear main seal

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Re: Sound File - what is making this sound?

Post by malmac »

wa1nca wrote:
Tue Nov 01, 2022 3:03 pm
I recall their was a post about breather noise after a new rear main seal was replaced (mostly at low rpm's)and was sort of normal but should go away after some time

If you removed the oil dipstick and the sound goes away it most likely because of the new rear main seal

Tommy
I tried the dip stick out start up. I am getting a lot of air coming out but the sound I have been hearing was still there.
I will do the leak down test and see how much blowby I have - new rings, pistons and rebore and hone - so maybe running in will improve that situation.

Thanks for the suggestion.

Mal
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