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> strange sound, anybody know this tac tac tac
michelko
post Jan 8 2005, 09:33 AM
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Hi guys,
today i fired up the spare engine. Makes a strange sound like tac tac tac.
Anybody knows what it could be? Think it comes from the right head. Valves are fresh adjusted.
Videofile

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Root_Werks
post Jan 8 2005, 09:50 AM
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Too much lash. Should be a nice little tickle, tickle, tickle sound, not a tac, tac, tac. Check those adjustments again. I would say they are too big and need to be snugged up just a tad. (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)
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michelko
post Jan 8 2005, 10:03 AM
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Hi Dan,
are you sure it´s the valve clearance? I measured the clearance twice. 0,15 mm cold. A friend suggested a broken piston ring? I have no experience about that sound. Is this possible?

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michelko
post Jan 8 2005, 10:19 AM
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here is a link for an 6 minute video warming up the engine and idling.
It is approximately 8 mb!!

warmin up

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Root_Werks
post Jan 8 2005, 10:54 AM
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...Hang on.... downloading now..... (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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Root_Werks
post Jan 8 2005, 11:03 AM
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I dunno man, it sure sounds like valve lash to me. It gets quieter as the engine warms up. Plus, when you give it a little throttle, I don't hear anything. So I don't think you have a bad wrist pin or rod knock etc. Those stick out like a soar thumb when you bump the throttle.

.015, dang, I am at work right now and can't remember the conversion. Is that .006"? Most people I know do .006 across the board, but if you live in a cooler climate, I would go .004 intake and .006 exhaust. Pop off a valve cover and check the #1 again. Maybe it is the rockers? It is valve train noise for sure though. I have heard that a bazilion times. Other than that, motor sounds great! (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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jr91472
post Jan 8 2005, 11:09 AM
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Mild hijack (please forgive).

Is it true that over time as the valves get "out of adjustment" that they actually get tighter? not looser?

I adjusted my valves two weeks ago and they were all sitting at .003-.004.

thanks

oh, cool test setup on the engine. (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif)
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michelko
post Jan 8 2005, 11:21 AM
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yes 0,006 is 0,15 (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif) (inch vs. mm)

thanks for advice, i will check that stupid valves again (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif)

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SirAndy
post Jan 8 2005, 01:09 PM
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QUOTE (michelko @ Jan 8 2005, 09:21 AM)
i will check that stupid valves again

that doesn't sound good ...

rod-knock? i had an engine that sounded similar after it lost a rod-bearing ...
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Dave_Darling
post Jan 8 2005, 01:17 PM
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QUOTE (jr91472 @ Jan 8 2005, 09:09 AM)
Is it true that over time as the valves get "out of adjustment" that they actually get tighter? not looser?

Nope. They can go either way. If you have one or more valves that consistently gets looser--or that consistently get tighter, then you have a cause for worry...

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michelko
post Jan 9 2005, 04:23 AM
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QUOTE (SirAndy @ Jan 8 2005, 11:09 AM)
QUOTE (michelko @ Jan 8 2005, 09:21 AM)
i will check that stupid valves again

that doesn't sound good ...

rod-knock? i had an engine that sounded similar after it lost a rod-bearing ...
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Hi Andy,
how can i diagnose this without opening the engine?
Any ideas?

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r_towle
post Jan 9 2005, 12:30 PM
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Sounds like valves and a rod.

Check the compression/leakdown test
this will help you diagnose the issue.

I would adjust the valves again making sure you are TDC when you do each one.

Rich
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newdeal2
post Jan 9 2005, 01:38 PM
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QUOTE (Root_Werks @ Jan 8 2005, 09:03 AM)
I dunno man, it sure sounds like valve lash to me. It gets quieter as the engine warms up. Plus, when you give it a little throttle, I don't hear anything. So I don't think you have a bad wrist pin or rod knock etc. Those stick out like a soar thumb when you bump the throttle.

.015, dang, I am at work right now and can't remember the conversion. Is that .006"? Most people I know do .006 across the board, but if you live in a cooler climate, I would go .004 intake and .006 exhaust. Pop off a valve cover and check the #1 again. Maybe it is the rockers? It is valve train noise for sure though. I have heard that a bazilion times. Other than that, motor sounds great! (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

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Sounds a little like my engine as it's warming up. I recently adjusted my exhaust valves to .008 and that's what they sound like. It does quite down quite a bit when warm/accelerating.

I assume this is a fresh rebuild?
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michelko
post Jan 9 2005, 02:27 PM
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QUOTE (newdeal2 @ Jan 9 2005, 11:38 AM)
QUOTE (Root_Werks @ Jan 8 2005, 09:03 AM)
I dunno man, it sure sounds like valve lash to me.  It gets quieter as the engine warms up.  Plus, when you give it a little throttle, I don't hear anything.  So I don't think you have a bad wrist pin or rod knock etc.  Those stick out like a soar thumb when you bump the throttle.

.015, dang, I am at work right now and can't remember the conversion.  Is that .006"?  Most people I know do .006 across the board, but if you live in a cooler climate, I would go .004 intake and .006 exhaust.  Pop off a valve cover and check the #1 again.  Maybe it is the rockers?  It is valve train noise for sure though.  I have heard that a bazilion times.  Other than that, motor sounds great!  :)

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Sounds a little like my engine as it's warming up. I recently adjusted my exhaust valves to .008 and that's what they sound like. It does quite down quite a bit when warm/accelerating.

I assume this is a fresh rebuild?

no fresh rebuild. Don´t know how much miles it has.
I read something about different engine noise in a book called How to rebuild your aircooled engine from Tom Wilson.
I will check these advices.
I hope it is not to bad.

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Cap'n Krusty
post Jan 9 2005, 03:58 PM
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Noises can be difficult to pin down. You need to determine whether they're at crank speed or cam speed. In this recording it certainly sounds like valve noise, but the possibility of a piston being upside down is also there. Without knowing the RPM and the location of the mic, it's difficult to tell one sound from another. I know the rods aren't directional, but I'm pretty sure the pistons are, and they'll make a noise like this at piston speed. This clatter, however, sounds more like cam (or valve) speed. One way to locate a lower engine noise is to run it at a steady speed where the noise is obvious, and remove the plug wires one at a time. A rod or piston noise will lessen or disappear as that cylinder goes dead. A big-end rod noise will also be stronger when you snap the throttle open. Another common cause of noises such as this one is a worn or improperly sized wristpin bushing. Many people fail to have the rods reconditioned when they replace the pistons. While the big ends of T4 rods rarely need resizing (unlike 356/912 motors), the little ends are usually out of tolerance, and wrist pins are notoriously variable in diameter from set to set. The Cap'n
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