Re: [ST] Valve design

["B Parker" <bparker15@xxxxxxx>]

i don't dispute the condition of the valves and seats, but the cause is
not so certain. my uninformed guess is that a design flaw would have
surfaced in several STs, RSs, etc., before now [Dan W - how did your
valves look?]; it is more likely a manufacturing error in materials or
process. Ducati has had some severe problems with desmo parts when they
outsourced. my '67 Triumph had cam material problems - at 15,000 miles the
exhaust cam profile looked like a hex nut. my '84 BMW needed a valve
adjust every thousand or so miles because of the way i was riding [WOT /
red line too much]; it was eating valve seats, again a known problem.

springs without enough preload or return force at full open would show up
with valves slamming shut, deforming the sealing surface, when they were
thrown off the ramp of the cam because the spring force wasn't enough. but
this would typically be a high rpm problem, which Mike didn't do much of.

lots of work has gone into spring resonance, nested springs,
between-spring flat spirals, etc.; with the body of knowledge available to
Triumph by the time this engine design was finalized, springs should have
been pretty much a cookbook choice. it will be interesting to hear their
response [i think it would be in all our interest for sample valves,
springs, and seats to be sent to them].

cheers
pd
Sr Design Engr...but not of internal combustion engines.


>On Fri, May 16, 2003 at 05:19:31PM -0700, Mike Benzon wrote:
> Actually, I look forward to putting the bike back together with a better
design valve set up and riding it for many more miles.

<snip>

> I am not interested in Triumph's help. I prefer to rebuild with better
> parts, not put back the same flaw.  Mike

There are probably many others, though, would be curious to see what ToA
says about the whole matter.

Laters,
Brian<


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