Subject: Re: bearing damage?
Author: Patrick Hayes
Date: Apr 21, 2005, 10:29 PM
Post ID: 1718743059
Todd Nordwig wrote:
| Next question......how big a deal is it to repair this and is there an up grade bearing unit that can be used? And why did this one fail at 6000 miles? |
Well, I'm not sure we have yet determined what has gone wrong or how
much damage has been done. I would like to hear more about the symptoms
and I would like to hear more about how you are handling ALL THREE
adjusting locations in the clutch system.
If it is only the throwout bearing, then it is easy enough to just
replace it. Pull the swing arm. Remove the outer rear body and
bearing. Sometimes a magnet works. Sometimes you blow a little
compressor air into the transmission to inflate it and blow the bearing
out the back. Insert a new bearing and a new o-ring on the outer body.
That presumes you have the radial needle bearing from the later 4-speed
and all of the 5-speed transmissions. If you have the earlier 4-speed
caged ball bearing, then you're screwed. That bearing is no longer
available. You can tear down the transmission and have the rear cover
machined to a larger diameter so that you can utilize the newer bearing
and later version throwout parts.
There can be other damage consequences. If the bearing fails, then the
inner throwout shaft binds and is prevented from turning in synch with
the engine. I have seen this shaft act as a drill bit and bore itself
right through the clutch. I have seen this shaft heat-weld itself right
into the clutch. I have seen this shaft abrade away several millimeters
from its contact tip. Those few mm in the clutch throwout translate
(via leverage effect) to huge dimensional changes in the cable system.
Lets hope you haven't done any of those problems.
The primary reason for failure of the throwout bearing is over-adjusting
the clutch lever and cable too tight. The bearing is designed for
intermittent use, not constant load. Very easy to tighten the clutch
freeplay to zero and force this bearing to spin constantly. Won't last
long that way.
BTW, how do you handle your bike during prolonged clutch use? You come
to a traffic light that just turns red as you arrive. You know there is
heavy cross traffic and it will be awhile before you get a green. Do
you just sit there with you clutch hand pulled in and wait? Two
minutes? Three minutes? How much effect do you think this has on the
poor little bearing? If I can't predict green within 10 seconds, then I
instantly shift to neutral and release the clutch to unload the bearing.
Also, due to the design of the Guzzi clutch, as the friction plates
wear, the throwout system moves aft and takes up any slack in the cable
system. You have to be attentive to loosening up the cable play as the
clutch wears. The most dramatic rate of wear occurs in the first few
thousand miles after new plates are installed. Ignore the loss of
freeplay and you have doomed the bearing.
Patrick Hayes
Fremont CA