Subject: Re: Digest for Loopfram-@topica.com, issue 1158
Author: PEHA-@aol.com
Date: May 8, 2003, 8:41 AM
Post ID: 1712914607
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In a message dated 5/8/2003 4:44:00 AM Pacific Daylight Time,
mjon-@yahoo.com writes:
| Pat, the gap adjusts timing for the second cylinder - if the gap is in range according to the manual the timing can still be off a little because there is a "range" to what gap is supposed to be acceptable. If the gap is perfect, then that will not be the case, but getting it perfect is why you need to time both cylinders. This is not controversial - even Frank W. endorses this method. |
Sorry, don't buy it. And, BTW, Frank Wedge was once known to put police
handlebars and a double bucket touring seat on his LeMans 1! (Don't worry,
he's a longtime friend.) Here's the problem. I dislike use of the term
"second cylinder" for semantic reasons. The loopframe Guzzi is timed by the
left side cylinder. (by convention, left and right, sinistro and destro, are
always referenced to the rider astride the bike) Since both connecting rods
attach to the same crank journal, side-by-side, one has to be centered more
forward than the other. Oddly, the left side cylinder is further back on the
crank and could confusingly be called cylinder #2. Hence my concern about
"second cylinder" usage.
Now as to timing. Let us imagine you have absolutely, perfectly set the
point gap and the ignition timing for the left hand cylinder. If you
thereafter do ANYTHING to alter the rotational position of the distributor or
the clamp screw of the points, you will destroy the precision of your timing
effort for that left cylinder. So, if you now rotate the engine to bring the
right side cylinder into spark position and if you find it is not sparking at
the precise correct point, what are you going to do? If you change the gap
to alter the timing on the right side, you have just screwed up the left side
timing. If you turn the distributor to alter the right side timing you have
just screwed up the left side timing.
The ONLY thing you could do to alter the timing of the right side without
effecting the timing of the left side would be to recreate the distributor
drive shaft with one of its cam lobes in a slightly varied rotational
position or lift altitude. (Don't try this at home, kids.)
So, what do you do if you inspect and find that the timing of the right
cylinder is not precise after you have timed the left cylinder? You have two
options. "A", you can realize that this is a very low stress motor and that
the fuel you are using today is not the same as the fuel the engineer
designed to in the 60's and its not really going to make a whole lot of
difference and just ignore it and go ride and ..... or "B" let us suppose
after your left side perfection work that you now find the right side to be
two degrees too retarded. (there is a two degree error separation between
the two sparks) You can now go back to the left side to re-time and split the
difference. Set the left side one degree too advanced and now the right side
will be only one degree too retarded. A good compromise. See? You CANNOT
alter the two degree error in the relationship between the two cylinders
other than by distributor shaft alteration. Not by turning the distributor,
not by moving the points.
Although the parts are in rotational operation, it is all just straight
linear math. You CANNOT alter the relationship between the two sparks.
After you set the left side perfectly, they are either both perfect or you
have a slightly erroneous distributor cam and can only split the error to
correct.
The later Tonti framed bikes use two sets of points mounted on two separate
floating plates in the distributor. It allows you to absolutely, perfectly
gap and time the left cylinder and the right cylinder fully independently.
Your instructions sound much like the hideous V35/V50/V65 small blocks. They
used two sets of points, but they were both mounted on the same rotational
plate. So, as you describe, you could perfectly time the left side and then
you could perfectly time the right side by altering the gap for the points of
the right side cylinder. It was a crappy system, fraught with compromises.
The small blocks absolutely BEG for conversion to electronic ignition.
Patrick
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<HTML><FONT FACE=arial,helvetica><FONT SIZE=2>In a message dated 5/8/2003 4:44:00 AM Pacific Daylight Time, mjon-@yahoo.com writes:<BR>
<BR>
<BR>
<BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Pat, the gap adjusts timing for the second cylinder -<BR>
if the gap is in range according to the manual the<BR>
timing can still be off a little because there is a<BR>
"range" to what gap is supposed to be acceptable. If<BR>
the gap is perfect, then that will not be the case,<BR>
but getting it perfect is why you need to time both<BR>
cylinders. This is not controversial - even Frank W.<BR>
endorses this method.<BR>
</BLOCKQUOTE><BR>
<BR>
Sorry, don't buy it. And, BTW, Frank Wedge was once known to put police handlebars and a double bucket touring seat on his LeMans 1! (Don't worry, he's a longtime friend.) Here's the problem. I dislike use of the term "second cylinder" for semantic reasons. The loopframe Guzzi is timed by the left side cylinder. (by convention, left and right, sinistro and destro, are always referenced to the rider astride the bike) Since both connecting rods attach to the same crank journal, side-by-side, one has to be centered more forward than the other. Oddly, the left side cylinder is further back on the crank and could confusingly be called cylinder #2. Hence my concern about "second cylinder" usage. <BR>
<BR>
Now as to timing. Let us imagine you have absolutely, perfectly set the point gap and the ignition timing for the left hand cylinder. If you thereafter do ANYTHING to alter the rotational position of the distributor or the clamp screw of the points, you will destroy the precision of your timing effort for that left cylinder. So, if you now rotate the engine to bring the right side cylinder into spark position and if you find it is not sparking at the precise correct point, what are you going to do? If you change the gap to alter the timing on the right side, you have just screwed up the left side timing. If you turn the distributor to alter the right side timing you have just screwed up the left side timing.<BR>
<BR>
The ONLY thing you could do to alter the timing of the right side without effecting the timing of the left side would be to recreate the distributor drive shaft with one of its cam lobes in a slightly varied rotational position or lift altitude. (Don't try this at home, kids.)<BR>
<BR>
So, what do you do if you inspect and find that the timing of the right cylinder is not precise after you have timed the left cylinder? You have two options. "A", you can realize that this is a very low stress motor and that the fuel you are using today is not the same as the fuel the engineer designed to in the 60's and its not really going to make a whole lot of difference and just ignore it and go ride and ..... or "B" let us suppose after your left side perfection work that you now find the right side to be two degrees too retarded. (there is a two degree error separation between the two sparks) You can now go back to the left side to re-time and split the difference. Set the left side one degree too advanced and now the right side will be only one degree too retarded. A good compromise. See? You CANNOT alter the two degree error in the relationship between the two cylinders other than by distributor shaft alteration. Not by turning the distributor, not by moving the points.<BR>
<BR>
Although the parts are in rotational operation, it is all just straight linear math. You CANNOT alter the relationship between the two sparks. After you set the left side perfectly, they are either both perfect or you have a slightly erroneous distributor cam and can only split the error to correct.<BR>
<BR>
The later Tonti framed bikes use two sets of points mounted on two separate floating plates in the distributor. It allows you to absolutely, perfectly gap and time the left cylinder and the right cylinder fully independently.<BR>
<BR>
Your instructions sound much like the hideous V35/V50/V65 small blocks. They used two sets of points, but they were both mounted on the same rotational plate. So, as you describe, you could perfectly time the left side and then you could perfectly time the right side by altering the gap for the points of the right side cylinder. It was a crappy system, fraught with compromises. The small blocks absolutely BEG for conversion to electronic ignition.<BR>
<BR>
Patrick</FONT></HTML>
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