Lemans III Rear Main Flange Leak

[RacetouringATX]

Hi Folks,

I am a bit new to the new forum but have enjoyed drilling into the information shared.  I believe I have a good story to share after just wrapping up a rear main leak on a '84 Lemans III.  I was able to pickup a very nice Lemans in April 2020 in Ft. Worth.  I flew up and the current owner picked me at Love Field.  The current owner only had the bike for a year or so and had sourced if from the original owner in the north east, so essentially a one owner bike.  The Lemans is in great original condition with no known issues.  I paid with a cashiers check and headed back to Austin on one of my dream bikes. 

I knocked down about 150 miles on the super slab and stopped at one of Tejas' new giant rest areas to stretch.  When I pulled myself off the bike I noticed oil all over the rear of the bike, ughhhh.  I checked the oil and nursed it back home, stopping several times for oil checks.  I made it safely home in the late evening, although disappointed I figured the rear main seal had gone.  The bike is in nice original condition so the main seal dried out, right?  Oh, the bike has less than 8,000 documented miles. 

I finally found time over the - Turkey Day Holiday 2020 to tear into the bike.  This is what I found.  I guess I got a Friday bike and the Italian was still hungover on Monday when the person put the flywheel on.........  This funky bolt had been rattling around in the space between the rear main flange and flywheel since 1984, wow.  It took me about 6 weeks to source all the parts and tools to complete the job, finished this last weekend. 

The bike is running great and what an amazing machine.  I will be registering it soon and enjoying this awesome machine.  I want to thank the original owner for taking such great care of this machine.  It will stay in my stable for many years to come as my most coveted machine.

Thanks for sharing your Guzzi knowledge on this forum. 

GuzziATX

[jwinwi]

Congratulations on the purchase and welcome to WG!
The errant bolt punched a hole through the bearing carrier?

[lucian]

Nice find, congratulations. Was it the paper gasket under the bearing flange leaking or the main seal on the crankshaft? Curious as I am doing a clutch on a LMIII currently. Hard to believe the factory left the bolt in there. Perhaps someone dropped it through the starter hole at one time. That 850 is one of Guzzi's finest motors IMO.

The errant bolt punched a hole through the bearing carrier?

 Sure looks that way, there is an oil return gallery right there that drains the outboard side of the crank bearing. That's why it's important not to set the seal in too far and block the drain hole.

[fotoguzzi]

Is there any marks on that side of the flywheel? Or how did the errant bolt get a pointed end? Where was the leak from, that hole above the bolt?

[lucian]

Is there any marks on that side of the flywheel? Or how did the errant bolt get a pointed end? Where was the leak from, that hole above the bolt?

Looks like the bolt wedged between the flywheel and bearing carrier ,punched through the oil passage in the carrier flange and rounded the end of the bolt in doing so. What an unfortunate thing to have happen, could have been worse for sure.

[Scout63]

Nice sleuthing ATX.  It sounds as if the sump oil never got too low so probably no harm done.  Looks as if the screw got punched into the bearing carrier by the flywheel as said before. 

This is a a WAG, but maybe the screw is part no. 620330 carb mounting screw (p. 10, part18):

https://www.thisoldtractor.com/mg_manuals/spare_parts_catalog_lemans_iii.pdf

that got dropped into the timing hole during maintenance.

[RacetouringATX]

Yes.  The weird bolt, maybe an alignment tool, not sure, punched a hole in the flange.  See the bolt pics, weird star shape.  The flywheel had a light grove along the back so it was in there a while.  The bolt is very smooth on the ends, bouncing around I guess.   I can't see how the bolt could have gotten in there with the flywheel in place but I don't really know and I like the story that I have fabricated . 

The paper gasket was there and was not leaking.  It came off very easy and the surfaces cleaned up nicely. 

I was worried about the main seal install but it seems to be okay.  I did buy the MGCycle install tool. 

Cheers.

[Tom H]

The picture makes me think it's a Torx. Is it??? Why would a Torx of that size be there? I thought Guzzi always used allan except on the FI TB assembly, and those are small??

Tom

[jwinwi]

Finding it *very* hard to believe that bolt got in there at the factory...

[lucian]

Uhmm, you did replace the bearing carrier flange I hope.

[RacetouringATX]

No idea how it got there but it was sitting on the lower portion of the flange behind the flywheel.  The rear main seal seemed to be the old style and I spoke with the original owner and he stated that he was not aware of any clutch work.

I did replace the rear main flange, seems to working great.

Cheers.