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Author Topic: valve clearance question  (Read 27643 times)

Strycker

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Re: valve clearance question
« Reply #10 on: October 23, 2009, 01:05:31 PM »

Knock on wood, but I haven't checked mine yet  ::)  Prob should.  About to roll over 8000 miles.  Haven't ragged or abused the bike though.  Still runs like when I bought it.
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BradCCM

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Re: valve clearance question
« Reply #11 on: October 23, 2009, 04:33:15 PM »

 :)
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newbymick

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Re: valve clearance question
« Reply #12 on: October 24, 2009, 02:43:09 PM »

22500 miles and -  check valves - what for - haven't heard them rattling.  What is it the 'ol man used to say "if it ain't broke"  ;) ;)

Must get the GT out more often  ;)

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"I read somewhere that 77 per cent of all the mentally ill live in poverty. Actually, I'm more intrigued by the 23 per cent who are apparently doing quite well for themselves."
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stigger

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Re: valve clearance question
« Reply #13 on: October 24, 2009, 04:02:05 PM »

Yeah but whe. You've had 2 heads let go you tend to get a bit paranoid about such things...
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newbymick

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Re: valve clearance question
« Reply #14 on: October 24, 2009, 04:14:51 PM »

Can we sticky this to the thread?  Good info.

Job done for yer  ;)
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"I read somewhere that 77 per cent of all the mentally ill live in poverty. Actually, I'm more intrigued by the 23 per cent who are apparently doing quite well for themselves."
Jerry Garcia

BradCCM

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Re: valve clearance question
« Reply #15 on: October 24, 2009, 05:58:49 PM »

22500 miles and -  check valves - what for - haven't heard them rattling.  What is it the 'ol man used to say "if it ain't broke"  ;) ;)

Must get the GT out more often  ;)



These are not like tappet valves where the tappet itself is the weakest material, and wears  out first, making the clearance get loose and get a rattling sound.  Being shim under bucket, Wouldn't you be more concerned that they are too Quiet? Meaning the the weakest part in the this style system is the valve seat, or the valve itself. So if the material of the valve itself or the seat is wearing out, that would make the valve move up toward the cam making less clearance.  Every bike I have adjusted was too tight, some with no clearance at all, Those are the ones that we will see with a burnt up valve, because the valve is not shutting all the way (one customer did not do one valve clearance check until 15000 mi, also did not get covered under warranty because if he did check it, it may not have burnt the valve).  When you have a tight valve you would never hear a rattling sound, it would be almost silent...   :)
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BradCCM

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Re: valve clearance question
« Reply #16 on: October 24, 2009, 08:05:00 PM »

To understand shim over bucket, shim under bucket, and tappet... Here are some diagrams to help understand if you dont know.

This would be a tappet system, using a rocker arm.  These are the ones that you will get the most ticking or rattling sound.  It has much more moving parts above the valve that can wear, causing a loose valve.



This would be shim over.  The problem with this is at a high RPM if you get valve float, the shim can pop out and hang the valve open. Usually you will not see this type with a rev limit over 8000rpm.



this pic kinda shows how the shim can pop out... Also that you can compress the spring with special tool and adjust the shim without removing the cams.



Shim under bucket is the most reliable and allows engines to rev to a higher RPM... In this diagram you can see that the shim would be installed under the bucket and sit ontop of the valve, this is why you have to remove the cams to do an adjustment



I decided to add this too...  this is a desmodromic system, what Ducati uses.  This can rev much higher than a shim under bucket because it does not us a valve spring.  In Moto-GP honda complained that there should be a rev limit on bikes, because the Ducati could rev over 20,000RPM with no valve springs, using an opening and closing cam and rockers instead of a valve spring to close the valve... Valve springs start to float at about 18,000 RPM and can not keep up with the high RPM.


« Last Edit: October 24, 2009, 08:18:14 PM by BradCCM »
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newbymick

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Re: valve clearance question
« Reply #17 on: October 25, 2009, 10:50:45 AM »

When you have a tight valve you would never hear a rattling sound, it would be almost silent...   :)

Well, that makes so much sense that I'm going to have a look right now.  Damn these new fangle engines for being so well engineered  ;) ;)

Thanks for the heads up Brad  ;D
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"I read somewhere that 77 per cent of all the mentally ill live in poverty. Actually, I'm more intrigued by the 23 per cent who are apparently doing quite well for themselves."
Jerry Garcia

BradCCM

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Re: valve clearance question
« Reply #18 on: October 25, 2009, 07:44:11 PM »

I thought this pic was cool... this is out of a RM450 dirt bike.

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BradCCM

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Re: valve clearance question
« Reply #19 on: November 05, 2009, 02:18:17 AM »

When you have a tight valve you would never hear a rattling sound, it would be almost silent...   :)

Well, that makes so much sense that I'm going to have a look right now.  Damn these new fangle engines for being so well engineered  ;) ;)

Thanks for the heads up Brad  ;D
Question.
When doing an adjustment.
Do you adjust to the upper end of the tolerance?
Or a middle clearance?
Shims are available in .002 increments.
So thought I'd pose the question to a pro.

Personally I try to do the loose side of the adjustment, for street riders. On the race bike, I do tight side, because the valve opens farther when you are on the tight side....   :)
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