Subject: Name that tune (sound) solved!
Author: kcampbellNH
Date: Mar 25, 2004, 5:32 PM
Post ID: 1716399893
Thank-you to all who replied to my post a few weeks ago. Even though I
was sure it was not a rod bearing, it did not sound like any rod knock I
had heard before (sounded nothing like a Chevy small-block rod), but
that is what it was. So if you are interested, and at the risk of ending
up on MG Cycles "Cobb Page", the following is how I repaired it.
I grew up on a dairy farm where we had fleet of old Farmall tractors and
we ran the wheels off them. Occaisionally we rebuilt the engines and
routinely shimmed the bearings to save time and money. I consulted with
a few different Guzzi Gurus about trying it on the Eldo and as expected
got mixed opinions. But since it is my "winter bike", I plan on keeping
it, I don't beat the thing, and figured the worse thing that could
happen was I would have to get a new crank or have mine cut anyway, and
I did not want to pull the engine, I decided to try the shim trick on
it. It goes something like this.
* The journal did not look too bad so I measured it with a digital
caliper (never had those on the farm aye-uh) and determined it was worn
about .003" under spec.
* Checked to see if it was reasonably round and paralell (not so easy
while the engine was still in the bike and fully assembled except for
the right hand jug and oil pan)
* Obtained new standard rod bearing inserts, installed them in the rod,
torqued it and measured the inside diameter.
* Plugged the oil holes in the journal with grease so nothing would get
into the oil passages in the crank.
* Laid a fine file to the journal while my helper turned the motor over
to rotate the crank(turning the rear wheel in 5th gear with the left
spark plug removed) to knock down the tiny ridges left on the journal.
* Followed that with fine (320) emery cloth tape, back and forth again
while the crank was rotated.
* Followed with finer (or dull 320) cloth the same way until the journal
shines like chrome.
* Measure the journal again and compare that # to the ID of the rod with
the bearing installed and determine the difference.
* I needed to make up about .003 to get back to the .0015 to .0025" the
original clearance spec.
* I begged a scrap of .0015 steel shim stock from a local machine shop
rather than buying a roll from some place like Grainger (on the farm we
would use tin cans!).
* Cut two shims to fit perfectly under the bearing shells.
* Working with the rod cap first, install the bearing and the shim and a
bolt with a washer on the side with the tab first so that the shell
stays flush with the mating surface of the cap followed by the other
side and note that the bearing is too high for the washer to sit flush
on the mating surface due to the shim raising the bearing.
* Carefully file down the excess until the shell fits flush in the cap
with the bearing and shim installed.
* Repeat the process on the connecting rod with the other bearing half.
* Clean grease out of the oil holes in the journal, a bulb syringe and a
pipe cleaner do the trick.
* Install the connecting rod on crankshaft and check for adequate
clearance. Plastigage would work. In my case the clearance was tight so
after rotating the crank a couple of times I pulled the rod off and
looked at the bearing to see where any contact was. I repeated the emery
cloth again, concertrating on the edge of the journal that was making
contact until I was able to turn the rod on the crank. I figured the
break-in and setteling of the shim would result in adequate clearance.
* Retorque the rod and complete the final assembly.
I have ridden 50 miles and it is working great. The motor is quiet! The
only question now is will the repair last the long haul. I am guessing
it will. I will keep you posted. Ride Safe.
Kevin
98 EV
97 Sporti
80 v50++
75 T-3
74 Eldo