ADVrider

Go Back   ADVrider > Bikes > Old's Cool > Airheads
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 02-14-2010, 07:55 PM   #61
pommie john OP
Beastly Adventurer
 
pommie john's Avatar
 
Joined: Apr 2008
Location: Brisvegas, Australia
Oddometer: 1,410
Here's the crack.





It extends between the two red arrows. Up under the rim near the breather housing, and down, right across the rim at the bottom.





Here it is in close up.






I've already had a chat with the local indy BMW shop and they've got plenty of cases. They will sell me one at a very good price.
pommie john is offline   Reply With Quote
Old 02-14-2010, 08:55 PM   #62
Infracaninophile
Finding My Way..
 
Infracaninophile's Avatar
 
Joined: Sep 2001
Location: New England, USA
Oddometer: 7,513
Any idea of the root cause of the crack? Flaw during manufacture? Bike crash with impact to motor case? You can't seal it from the outside?

Tom
Infracaninophile is offline   Reply With Quote
Old 02-14-2010, 09:26 PM   #63
pommie john OP
Beastly Adventurer
 
pommie john's Avatar
 
Joined: Apr 2008
Location: Brisvegas, Australia
Oddometer: 1,410
Quote:
Originally Posted by Infracaninophile
Any idea of the root cause of the crack? Flaw during manufacture? Bike crash with impact to motor case? You can't seal it from the outside?

Tom

No. No idea. I have heard of another race bike that cracked too. Being a race bike it has crashed on numerous occasions, but nothing too hard. The hardest crash was a front end lose in the wet which cracked the rocker cover, but didn't smash it. I can't imagine that that would cause a crack in the crankcases.

It has been producing something like twice the designed power for about 15 years, so I can't complain too much.

I'm not inclined to try to repair it. Too much risk of distortion, and my local friendly welder curses me every time I bring him a piece of alloy that has been immersed in oil for 20 years.

I have been offered a replacement for $150. It'd cost that for the welding.
pommie john is offline   Reply With Quote
Old 02-14-2010, 10:26 PM   #64
jackd
Beastly Adventurer
 
Joined: Dec 2006
Location: North Cowichan
Oddometer: 3,031
That's quite the crack there. Does it start at the top right hand transmission mount hole? I've questioned Snowbum about whether the plugs which seal the oil delivery galleries for the top end ever leak and his response was that it was also quite rare. I'm going to give my case a major going over when I go back in. Thanks for posting these shots and good luck.
jackd is offline   Reply With Quote
Old 02-14-2010, 10:31 PM   #65
jackd
Beastly Adventurer
 
Joined: Dec 2006
Location: North Cowichan
Oddometer: 3,031
I just had a look at your previous shots from this thread, before you changed the rear seal. You can actually see the crack - it just hadn't opened up yet. I will definitely give mine a very close look.
jackd is offline   Reply With Quote
Old 02-15-2010, 11:23 AM   #66
Wirespokes
Beemerholics Anonymous
 
Wirespokes's Avatar
 
Joined: Jul 2002
Location: Jackson's Bottom Oregon
Oddometer: 8,036
The one I'd seen before had several cracks extending radially from the rear main.
__________________
Wanted: Dead, smashed, crashed or trashed gauges
BMW GAUGE REPAIRS - TACH*SPEEDO*CLOCK*VOLT METER *PODs & LIGHT BOARD*
Wirespokes is offline   Reply With Quote
Old 02-15-2010, 12:17 PM   #67
bereahorn
Beastly Adventurer
 
Joined: Mar 2002
Location: North Coast (Lake Erie)
Oddometer: 1,056
Subscribed

Subscribed
bereahorn is offline   Reply With Quote
Old 02-15-2010, 05:09 PM   #68
Max Headroom
lost in the '70s
 
Max Headroom's Avatar
 
Joined: Feb 2008
Location: New Zealand
Oddometer: 512
A friend of mine had an R100RS which developed a persistent leak some years ago. We initially suspected the rear main seal to be the culprit. After we'd replaced it twice along with the oil pump o-ring, we started looking elsewhere. We ran the engine with the flywheel fitted and the gearbox removed one Saturday morning and waited for a leak to appear. It revealed itself as a similar crack to Pommie John's engine, although on the other side of the rear main bearing straight through the oil gallery feeding the crank. I attempted to patch it up by removing the gallery plug and fitting a thin sleeve I'd machined to line the oil gallery, and although it reduced the leak substantially it wasn't a satisfactory solution.

I've often thought about the possible reasons for the crack appearing, and I now wonder if it hadn't been caused by getting too enthusiastic with a big hammer while removing and installing new crank bearings. The crankcase was never designed or intended to cope with too much pounding axially without proper support to localise the forces involved.

Just a thought . . .
__________________
'76 R90S silver smoke
'75 R90/6 hybrid

'Skills are learned, talent is ornate.' Billie
Max Headroom is offline   Reply With Quote
Old 02-15-2010, 08:09 PM   #69
jackd
Beastly Adventurer
 
Joined: Dec 2006
Location: North Cowichan
Oddometer: 3,031
Having replaced my seal more than a few times, I can say that I have given the area a pretty good going over. Unfortunately the area is squeaky clean and there is no tell tale stain in dried up clutch dust. I'm going to run it with the tranny off, as well - a real pain in the ass actually to set it back up with the exhaust going back on, battery back in, tank back on, etc. We'll see what I find when I try this. I'm really hoping not to find a crack. Some Porche owners have commented that the crank can settle (if it's worn) and leak for that reason. My bike only has 46K miles on it - it's still quite young in real terms. I'm somewhat pleased that I'm not the only one going through this little private hell.
jackd is offline   Reply With Quote
Old 02-15-2010, 09:45 PM   #70
wirewrkr
the thread-killer
 
wirewrkr's Avatar
 
Joined: May 2008
Location: HIGH desert
Oddometer: 4,295
What is that horrible sound?
Say it ain't so, but me thinks that the
SKY IS FALLING!!!!
__________________

www.wirewerkes.com
KILL YOUR TELEVISION !!!!
wirewrkr is offline   Reply With Quote
Old 02-16-2010, 03:39 PM   #71
pommie john OP
Beastly Adventurer
 
pommie john's Avatar
 
Joined: Apr 2008
Location: Brisvegas, Australia
Oddometer: 1,410
Quote:
Originally Posted by Max Headroom
... and I now wonder if it hadn't been caused by getting too enthusiastic with a big hammer while removing and installing new crank bearings. The crankcase was never designed or intended to cope with too much pounding axially without proper support to localise the forces involved.

Just a thought . . .

Good point. How much bashing does it take to fit a rear main bearing? When I rebuild my motor into a new ( old) crankcase it will need new main bearings, so I don't want to go through the same game again.
pommie john is offline   Reply With Quote
Old 02-16-2010, 05:49 PM   #72
Cogswell
Spudly Adventurer
 
Cogswell's Avatar
 
Joined: Jan 2005
Location: Riding with my pal Richard Cranium
Oddometer: 4,231
Well it certainly sucks that the case is cracked but,

You know your installation of the rear crank seal was not the cause and you now know the source of the leak.

Best of luck on a quick and hopefully no too expensive repair.


Mike
__________________
Cogswell Rides To Big Bend
See my airhead project here
Time Warp Vintage Motorcycle Club
The good thing is, your damn motor can't read. If it says oil on the container, it's pretty much OK to dump in there.... ED.
Cogswell is offline   Reply With Quote
Old 02-17-2010, 10:20 AM   #73
BOOTLACE
Bikie Scum.
 
BOOTLACE's Avatar
 
Joined: Dec 2005
Location: Methane Central..(Sth Gippsland)
Oddometer: 3,841
G'day John. That's bloody amazing, never seen the likes of it. Oh well, at least you now KNOW!
If you'd like to PM me your email, I can send you some pix from the Island. My work 'putr won't allow me to upload pix to photobucket or the like, so can't post any till I'm out of here.(Minesite..).
Back to the Island this weekend for flag waving at WSBK tests, then same the next weekend, for first round. WOOHOO!
__________________
bootlace
BOOTLACE is offline   Reply With Quote
Old 02-17-2010, 08:58 PM   #74
bmwrench
Beastly Adventurer
 
Joined: Nov 2006
Oddometer: 2,040
Quote:
Originally Posted by pommie john
Good point. How much bashing does it take to fit a rear main bearing? When I rebuild my motor into a new ( old) crankcase it will need new main bearings, so I don't want to go through the same game again.
You shouldn't need to use a hammer at all. If the case is hot enough, the bearing will drop in.
bmwrench is offline   Reply With Quote
Old 02-17-2010, 11:26 PM   #75
pommie john OP
Beastly Adventurer
 
pommie john's Avatar
 
Joined: Apr 2008
Location: Brisvegas, Australia
Oddometer: 1,410
Quote:
Originally Posted by bmwrench
You shouldn't need to use a hammer at all. If the case is hot enough, the bearing will drop in.
Excellent. Thanks for the info. Maybe I'll try it myself.
Am I right in thinking that I can just fit the same size bearing as the old cases have?
I have a good set of digital callipers but my micrometer is too small to measure the journals.
pommie john is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 02:37 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014