Terry Packer packertl2 at yahoo.com
Thu Feb 19 08:43:39 PST 2009


Concours were famous for this, including the one I owned for 11 years.
The thermostat plate has a small bypass hole drilled through it which
was too small. That resulted in the temperature differential of the
fluid on opposite sides being too great. That in turn resulted in the
thermostat cycling open and closed. The established fix was to drill
the bypass hole slightly larger and the thermostat would stabilize. I
never noticed this on my GPZ. But it sounds like your thermostat is
almost certainly in question.

One possibility is that your bypass hole may have picked up some gasket
or other blockage, in which case your's can simply be cleaned and reinstalled.

If you decide to replace the thermostat, I'd first check with COG,
Concour Owners Group, to verify the correct size of the bypass hole. It
would be a shame to install a new one and find the symptom persists.

Terry Packer


--- On Wed, 2/18/09, Simon White <swhite at consultant.com> wrote:
From: Simon White <swhite at consultant.com>
Subject: Fluctuation
To: gpzlist at micapeak.com
Date: Wednesday, February 18, 2009, 6:20 PM

Hi all,

I'd like a diagnosis on weird behaviour I've noticed this week.  My
temp gauge has started fluctuating slightly - maybe two widths of the needle -
while I'm riding at a constant speed.  I've noticed it mostly on the
freeway I take to work, but it previously doesn't move at all from the warm
position, unless I'm stuck in traffic.  I'm thinking the thermostat may
be sticking, but as I haven't struck this problem before I'd appreciate
other people's input.  As a side note, we had a week of +40°C days two
weeks ago (which made the daily commute rather uncomfortable), but the bike
behaved flawlessly.  It's only this week (tops of only 30°C, and very nice
riding weather) that the gauge has started acting up.  FWIW, I checked the
coolant and it seems fine.

'95 GPz1100 - It's big and blue, like a whale.
Melbourne, Australia

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