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Re: Valve Clearance (wrong assumptions)



Hi Dan,
Good point - I am probably completely wrong in my assumption/guess that it was the shims that were causing the problem. The symptom is certainly that the clearances are closing down to zero within 6000-8000mi of use, and that is causing burnt valves and loss of compression, so as you say this should be due to valve tip, head or seat wear.  I was just getting confused as it is the shims that are replaced.
Sorry about causing this confusion. I have no idea exactly what is causing this problem; I hope Triumph have a better idea and perhaps they could enlighten us?
Thanks for the explanation Dan!
Jonathan

>>> dan & ann curcio <curcio@xxxxxxxxxx> 08/07/99 17:18:02 >>>
Hi guys,
I think I need a little education on valve clearance problems on cycles.  From my experiences with DOHC car engines worn valve shims rarely cause significant valve damage.  Usually the worst problem I have seen is significant noise with reduced performance due to incorrect valve timing because the valves are closing too early and staying closed too long.  Usually, the only damage to the valve is a mushroomed tip from the excessive pounding due to the large clearance and this takes quite a bit of time to happen.  Burnt valves usually are caused by valve clearances that are too tight and the valve is not allowed to close fully into its seat causing leaking combustion gases to burn the valve/seat.  A worn shim should cause the valve clearance to increase instead of decrease, right?  If this is correct the burnt valves on the T509 and Daytonas were probably caused by valve tip, head, or seat wear causing tight clearances and the shims were not the culprits.  Please help me underst!
and
the worn shim/burnt valve problem with Triumphs as I don't have a service manual yet to see how the valves are configured.
Thanks,
Dan

Jonathan Schulster wrote:  I insisted on them checking the valve clearances since 8 of 12 on my T509 were out of spec by 9500km last year.... Triumph know that most 1997-98 bikes taken in for service at 10,000km (6,000mi) are showing serious valve shim wear on 509/595/955i models...  Of course if you leave it to 20,000km there is a good chance you have burnt out valves or permanently damaged engines, and all they will pay for (perhaps) is the cost of changing the shims!...They were selling bikes in 1997-8 will shims made of 'cheese' ....magazines, like Motorrad have done long-term detailed tests on the Daytona and sure enough the valves were partly burned out at 20,000km....The only good news is that the mechanic believes the 1999 model engines have changed source of valve shims and are lasting much better.




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