Subject: Re: huh?
Author: Patrick Hayes
Date: Aug 14, 2001, 12:46 PM
Post ID: 1707866811
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In a message dated 8/14/01 10:25:28 AM Pacific Daylight Time,
chopp-@hotmail.com writes:
| The problem is that when it gets hot, it pings under 4th gear acceleration. That says slightly advanced, or bad advance springs. It was suggested that Bob Nolan used a trick where he removed one spring and it cured that problem. |
Two issues.
Firstly, the distributor counterweight springs are designed to hold the
ignition retarded against the increasing centrifugal force of the weights.
Weak springs or removing one of the springs will only allow the system to
advance earlier in the rpm slope leading to pinging. New springs will hold
better against this force and will help control pinging.
Secondly, what's the age of your cylinder heads? A classic Guzzi problem is
that the valve stems wear their respective guides slightly oval. There are
no seals on these guides. The vacuum during the intake stroke pulls a little
oil mist from the rocker arm chamber, past the guide and mixes it into the
combustion mixture. Regardless of your fuel quality, the effective
combustion octane rating of this polluted mixture goes way down and leads to
pinging when hot. This oil leakage is microscopic and doesn't produce
exhaust smoke or high consumption rates, but it does cause pinging. Consider
valve work for a future project. Sorry.
Patrick
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<FONT FACE=arial,helvetica><FONT SIZE=2>In a message dated 8/14/01 10:25:28 AM Pacific Daylight Time,
<BR>chopp-@hotmail.com writes:
<BR>
<BR>
<BR><BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">The problem is that when it
<BR>gets hot, it pings under 4th gear acceleration. That says slightly
<BR>advanced,
<BR>or bad advance springs. It was suggested that Bob Nolan used a trick where
<BR>he removed one spring and it cured that problem.
<BR>
<BR></FONT><FONT COLOR="#000000" SIZE=3 FAMILY="SANSSERIF" FACE="Arial" LANG="0"></BLOCKQUOTE>
<BR></FONT><FONT COLOR="#000000" SIZE=2 FAMILY="SANSSERIF" FACE="Arial" LANG="0">
<BR>Two issues.
<BR>Firstly, the distributor counterweight springs are designed to hold the
<BR>ignition retarded against the increasing centrifugal force of the weights.
<BR>Weak springs or removing one of the springs will only allow the system to
<BR>advance earlier in the rpm slope leading to pinging. New springs will hold
<BR>better against this force and will help control pinging.
<BR>Secondly, what's the age of your cylinder heads? A classic Guzzi problem is
<BR>that the valve stems wear their respective guides slightly oval. There are
<BR>no seals on these guides. The vacuum during the intake stroke pulls a little
<BR>oil mist from the rocker arm chamber, past the guide and mixes it into the
<BR>combustion mixture. Regardless of your fuel quality, the effective
<BR>combustion octane rating of this polluted mixture goes way down and leads to
<BR>pinging when hot. This oil leakage is microscopic and doesn't produce
<BR>exhaust smoke or high consumption rates, but it does cause pinging. Consider
<BR>valve work for a future project. Sorry.
<BR>
<BR>Patrick</FONT>
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