RSRBOB,
Let's look at the situation a bit more logically and less passionately.
When you turn the screws on the throttlebody linkage what happens? The
angle of the throttlebody butterflies change affecting the amount of air
being drawn into the throttlebody, in turn affecting the vacuum level.
Consider this a "macro" adjustment. What happens when you turn the air
screws on the throttlebody? The ball within the by-pass air passage either
constricts the passage or opens the passage to allow less or more air into
the throttlebody below the butterfly. Consider this a "micro" adjustment.
Yamaha's instruction are predicated on the assumption that the throttle body
butterflies are set correctly at the factory or by the local Yamaha mechanic
(which is probably true when the bike is new) and so the only adjustment
that should be required by the owner or service mechanic, once originally
set correctly, is the micro adjustment using the air screws. Do you agree?
Now, consider this.
Case #1 The throttlebodies are disassembled. It becomes necessary to sync
the vacuum level using the throttlebody linkage screws. It may also be
necessary to adjust the air screws to fine tune the synchronization. Agree?
Case #2 Due to changes that occur over time through continuous use, items
begin to wear. As such, you find that no matter what you do with the air
screws, including removal, inspection, cleaning and even replacement, you
can't get the vacuum level to synchronize (this was the nature of the
problem stated by George Paramithas). It is now time to go to the
throttlebody linkage screws to synchronize the system at macro level.
Agree?
Jeff B.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
Sent: Thursday, June 28, 2001 7:35 PM
To: [EMAIL PROTECTED]
Subject: To Nick was Re: Throttle body sync
Nick,
It is true that humans build motorcycles and therefore are susceptible to
errors. By the same token, engineers are also human and also fall into that
same category. Your argument is much like the foil wrapped rabbit one would
receive at Easter... once you sink your teeth into it, you realize it is
really hollow. To conclude that the procedure detailed in the service manual
is flawed because humans build motorcycles and motorcycles have had recalls
is totally unfounded. Obviously just about any product that was ever mass
produced for any period of time could be subjected to a recall. Therefore,
it
is no longer relevant that because motorcycles have had recalls that Yamaha
did not know what they were talking about when they described the procedure
for synchronization. In the same light, just because it has a surge at low
RPMs does also not discount the validity of the service manual. The myriad
of
possibilities as to why it has a surge does not mean that the engineers
describing syncing did not know what they were doing. Allow us to get back
to
how a motorcycle acts when it is out of sync. It is characterized by two
main
symptoms. One being what is commonly referred to as a hanging idle. (I know
you know this, this is for the lurkers) A hanging idle is one where when the
engine is revved no load and the throttle released, the RPMs hang well above
set idle RPM and take too long to return to that set idle speed. The other
common symptom that would indicate sync to be in question would be poor
throttle response when attempting to take off from a stop. What is happening
in this case is that all the cylinders are not pulling their own weight and
some are trying to pull harder than others. This is not to be confused with
a
lean hesitation but does feel like the bike is just having a hard time
getting going.
To address the issue of things going wrong on a motorcycle, or widget, or
whatever, after it is produced. Things do go wrong, problems arise and parts
fail. Does it mean it is a bad product? Parts can fail due to defects in
material or workmanship, design and/or application/abuse. A concept for the
new motorcycle is thought up, has to go through an engineering stage where
they try to make someone's idea a real piece of machinery, then it gets
reviewed by a legal department to make sure it falls within their acceptable
parameters for safety, then marketing gets ahold of it and decides what they
want to sell it for and then sends it back to engineering to be changed to
fit all those criteria. Suffice to say the original concept was not was
ended
up rolling off the assembly line. Although the surge may be annoying, at
some
point in that process, it may have been a casualty due to emissions or
something along those lines. Sure they wish they could produce the perfect
motorcycle but the reality of that is perfection is not the same to
everyone.
Therefore, they have to compromise certain design facets to accommodate
other
design requirements. This is a fact. Virtually everything around you that
was
produced is a compromise. Whether the shortcomings bother you or not is
subjective.
One other problem here about the list and the Internet in general is there
is
no guarantee of credibility of individuals that post to it. Surely we would
like to think most people who do choose to post do so with the best of
intentions, but more than one hoax has been facilitated via the net. To
contradict technical information published by the manufacturer with little
more than seat of the pants data may be fine for some but not for everyone.
The manufacturer has tremendous liability and credibility at stake when they
put anything in writing. Cognoscente of that fact, everything published is
reviewed for accuracy and liability to prevent foreseeable problems
associated with misinformation. It seems inconceivable that they would
intentionally publish misinformation on their own product, especially if it
reduces performance or the information is incorrect to the point of not
doing
what it is supposed to do. I believe the fact that you own a Yamaha, which
is
only an assumption on my part, is a testament to what you believe about the
company. That they do produce a quality product worth owning that you are
proud of and provides pleasure for you.
