It's definitely true that too much oil on the cylinder walls will prevent
the rings from sealing, and if they don't seal, the tips will get hot enough
from the blowby to lose temper during the initial break in (like, the first
two minutes) and they'll probably never seal.
BMW motorcycles are the worst. The old airheads that I worked on (air
cooled, horizontally opposed--it's painful for me to think of these as a
classic) would smoke like mad if you didn't do everything just right, and
sometimes if you did. After boring and honing with great care and exactly
the right grit with exactly the right cross hatch angle I would wash the
cylinders with detergent and hot water and let them air dry so they got a
thin coat of rust, put a little moly lube on the skirts, and assemble the
top end dry. Squirt some oil on the rockers and guides, and fire it up. If
it started smoking in the first two minutes you had to decide whether the
customer was worth a free do-over, 'cause that's the only thing that would
fix it.
All the rest of your process sounds mighty good.
The advantage of ring lapping is that it increases the likelihood that your
rings will seat by a bunch. Once I got hip to it I never had to redo a
Beemer top end. The extra 20 minutes saved me beaucoup hours.
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Chuck Arnold
Sent: Tuesday, February 10, 2004 10:45 AM
To: 'Jack W. Drews'; FOT@autox.team.net
Subject: RE: breakin
So, now I am just about to break in my rebuilt engine. Just had the crank
turned and nitrited, new forget pistons, deck blocked, etc. Hope to start
it this weekend. My normal [normal, this is the second time in my life and
last in two years] process would be to squirt a little oil in each cylinder
before I put the head on, thoroughly lube the cam, put the head on, fill the
engine with oil through the tappet holes, spin the oil pump drive gear
manually to put oil everywhere, install the dizzy, open my preprimed
accusump, start the motor and run for 20-30 minutes at between 2 and 3000
RPM.
Given what you wrote below, is the only step I should skip the pre-oiling of
the cylinder walls?
Thanks,
Chuck
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Jack W. Drews
Sent: Tuesday, February 10, 2004 10:02 AM
To: FOT@autox.team.net
Subject: breakin
A couple of years ago I installed Total Seal rings in my engine and just
couldn't get them to seal at all. Turned out that it wasn't the rings'
fault, but rather the surface of the sleeves had a poor finish.
In the process of solving this problem, I talked to a motorcycle guy who
said that BMW motorcycles had this problem a couple of years ago, and when
he went to the BMW school they taught them their recommended startup
procedure to prevent this problem.
This procedure is to install the pistons in the cylinders with virtually no
oil on the walls and no oil on the rings. Just put one dab of oil on each
skirt. Then, upon startup, run the engiene 2500 - 3000 for two to three
minutes -- just what cam manufacturers recommend anyway.
I tried that on my own engine with great trepidation (I've been looking for
a chance to use that big word) and it worked fine. Since then I've built a
half dozen engines using that procedure and everything is cool. There has
been no evidence of early ring wear, either.
uncle jack
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