Engine oil leak...again.

[Stevex]

LM2, owned for the last 11ish years. It had a slight weep from the clutch housing lower drain for years which I lived with until
about 18 months ago. I then went into the back of the engine and diagnosed a leaking cam blank which I JB Welded.
Last winter I fitted some swan neck bars and the improvement in rider comfort was so improved that I've put more miles on the Guzzi this last year
than all the previous ones.
Problem is, the leak from that drain has now got worse, to the point where I've had to go back into the back of the engine, fully expecting a fubar'd
rear crank oil seal. However the leak is either still from the cam bung OR...the rear main bearing gasket has let go.
The pic shows what I found after going in, with puddles of oil either side of the cam bung where the top of the main bearing creates 2 small reservoirs. You can also see the JB Weld repair I did.
The top of the cam bung which wasnt JB'd is dry and the breather pipes are dry too.
There's only one way to see if the bearing flange gasket has gone and that it to remove the bearing flange, which after the problems I heard of others efforts to remove this,
is filling me with dread.
Can anyone suggest the easiest way to get this bearing off please, although using the crank as a 'punch' to knock it out is a no no for me?
Also, how easy is it to remove the cam bung, are replacements still available?

[Antietam Classic Cycle]

I've found two crankcases cracked where the main bearing fits it in, just to the right of the cam plug area. I only found the crack because I tipped the engine onto the front, filled the "bellhousing" with soapy water and pressurized the crankcase.

I use the factory tool to remove the rear main bearing, copies of it are available.



Not too difficult to make something similar.

New cam plugs are available, but like a "freeze plug" in a car engine, they are expanded by driving them into place.
https://www.stein-dinse.com/en/moto-guzzi-camshaft-plug-big-models/item-2-1434187-12003900-.html

[Wayne Orwig]

I learned years ago to gently pressurize the case to find leaks in there. I hate doing that job multiple times. I never found a cam plug leaking, but always JB Welded them while in there just in case.

[Stevex]

I learned years ago to gently pressurize the case to find leaks in there. I hate doing that job multiple times. I never found a cam plug leaking, but always JB Welded them while in there just in case.

Good idea, just got to work out a way.

[John A]

It looks like the cam plug is not sealed all the way around. Looks like sealant is only on the lower side. Also I’ve found loose cam plugs when I heated the area around the plug to help get residual out of the joint. When I’ve found a loose one l peen the edges with a little ball peen and reseal. It’s rare to have to replace the plug.

[bmc5733946]

I know that you said the breather is dry but that sure looks like breather oil to me. That hose and it's connection is any easy place to leak and not look like it. The collecting spot is what leads me there. Pressurized oil leaks at a pretty good rate and is usually easily spotted. If it only drips after riding and not much while running, there's your clue. Pressurizing the crankcase is a great tool. Hope you find it.

Brian

[pehayes]

I agree that the JB Weld sealing has to fully encircle the cam plug.
You are already suspecting the bearing carrier gasket.  You should note that most of the bearing carrier bolt holes are blind, dead bottom.  However, the bottom two bolt holes are drilled through fully into the crankcase air chamber and can pass oil even with a bolt in place.  LocTite makes a special 'Thread Sealant' for such purposes.  Those bottom holes would not likely show leak puddle up top, but you should be aware and tend to them if you take the bearing carrier off.
Lastly, with age and mileage the pistons/rings/cylinders will have normal progressive wear and will gradually bleed more and more compression down into the crankcase.  This builds more internal pressure and gradually pushes more and more leakage from the usual suspect leak points.  Do we have signs here of progressive wear?
Because of the off-sync cycling of pistons, the air space in the crank chamber pulses with pressure changes.  Adding a sump spacer drops the oil pan and the oil level mark by about an inch.  Simultaneously enlarges the crank air space by an equal inch.  I don't think the LM2 came with a sump spacer from the factory.  It is an easy substitution.  You just need the spacer, an extra gasket, and a set of similarly longer sump bolts (both perimeter and 4 central).  That modification alone might be enough to make your leakage tolerable.  Should be easy to find a sump spacer on the new or used market.

Patrick Hayes
Fremont CA

[Stevex]

The cam plug is not sealed on the top half but is thoroughly dry and I will seal it.
I know the breather pipes can leak, so I checked them closely and again they are thoroughly dry.
I have a sump extension fitted.
No obviously signs of internal combustion chamber wear, did a compression check on both cylinders a couple of years ago and got 195/200psi.
Thanks for the advice.

[n3303j]

Lots'a work to get in there on my V11EV.
So I:
Fully sealed cam bore plug in JB Weld.
Replaced gasket on rear bearing carrier.
Installed bottom two bolts with Permatex sealant.
Replaced rear main seal with Viton seal.
Replaced gasket in breather pipe flange with Petmatex & torque to specs.
Replaced deteriorating breather hose.
AND!
Replaced one way breather valve in rubber hose because the ball had worn into the seat to the point where it would stick closed and drive up crankcase pressures.

No more leaks! One and done

Replaced transmission seals and clutch as long as I was in there. Probably the last time I'll have to pull the engine?

[Antietam Classic Cycle]

Good idea, just got to work out a way.

It's really quite simple: plug the breather(s) and oil return line, find a plug with the same thread as the drain plug, drill and tap that for a Schrader valve, screw that into the oil fill hole, pressurize with a small pump.

[Stevex]

Ive just carried out a leak check. With the large bore drain pipe removed I blanked off its hole using an aluminium plate with a viton sheet gasket. This let by on the first attempt so I used some three bond to seal it. I left the oil level dip stick in place and put some air into the engine via the small bore pipe, yes I know it exits into the sump oil but it does the job. I used a cordless inflator set at 4psi. No sign of any bubbles anywhere, despite covering the engine rear with a washing liquid/water solution.
Im would increase the pressure but I think the inflators pressure output is constant.
When I turned the inflator off I could hear the pressure dissipate, so it is pressurising.
So, do I take it that the problem could indeed be a drain pipe leak coming from the breather. How much oil do these breathers produce? Is it possible the leak only occurs at engine running temp? I really dont want to rebuild this bike and still have a leak, but surely if the flange gasket or cam bung was leaking it would be quite apparent at ambient temp.
Edit: Ive just cleaned the soap solution and used a leak detector spray I had left over from my days as a gas engineer. If there was a leak, this stuff would give a definite indication and there was none anywhere.

[n3303j]

Check that the one way check valve in the crankcase vent line is not sticking shut.

[Stevex]

Check that the one way check valve in the crankcase vent line is not sticking shut.

Checked by blowing down it, slight resistance but it opens every time.

[n3303j]

Checked by blowing down it, slight resistance but it opens every time.

From what I understand the valve was redesigned into a configuration that wouldn't stick.
Don't know if blowing down the valve will be the equivalent to that ball bouncing off its seat 3,000 to 7,000 times per minute?

[Stevex]

From what I understand the valve was redesigned into a configuration that wouldn't stick.
Don't know if blowing down the valve will be the equivalent to that ball bouncing off its seat 3,000 to 7,000 times per minute?

Having felt the pressure, or lack of, required to open that valve I doubt it opens and closes every revolution. Im sure enough pressure is generated at fairly low revs to keep it open. Otherwise it wouldnt last 5 minutes.

[Wayne Orwig]

Good idea, just got to work out a way.

On most I can just pressurize the line going to the airbox. That pressurizes all of the breather lines to and from the frame also, so it gives them all a test. And it is easy to do.

[Stevex]

On most I can just pressurize the line going to the airbox. That pressurizes all of the breather lines to and from the frame also, so it gives them all a test. And it is easy to do.

LM2 has no airbox and no in frame stuff.

[Stevex]

Afrer carrying out a leak test with no obvious leak indications even using leak detector solution I have a question for those who have pressurised the crankcases and found an indicated leak.
How much of an air flow did you introduce into the cases?
Is a minimum flow, just enough to provide positive pressure in the cases enough to give a positive indication where there is one?
I have an air blower, originally made to dry off wet bikes. It produces a large air flow and would provide much more pressure. Should I contemplate using this?

[Antietam Classic Cycle]

Afrer carrying out a leak test with no obvious leak indications even using leak detector solution I have a question for those who have pressurised the crankcases and found an indicated leak.
How much of an air flow did you introduce into the cases?
Is a minimum flow, just enough to provide positive pressure in the cases enough to give a positive indication where there is one?
I have an air blower, originally made to dry off wet bikes. It produces a large air flow and would provide much more pressure. Should I contemplate using this?

5 psi was sufficient to find the leak on the two I tested.

[chuck peterson]

A friend solved a stubborn leak by spraying Hylomar across the surface area of the rear main bearing …casting leak was the only diagnosis he could imagine

https://hylomar.com/

[lucian]

you can remove the bearing flange by inserting two allen screws into the two flange holes with the treaded holes,and then using two of the flange bolt to push the flange off when they bottom out against the allen screws. heat the case thoroughly with a heat gun and you can also ice the flange before  advancing the bolts slowly and evenly.  While in there I would replace the trans input seal also . Also make sure you only drive the new main seal one millimeter past flush with the flange face as ther is a lubrication port for the bearing that will be blocked by the seal if drivin in too far


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[Stevex]

I have given  the blower a go into the dipstick hole. A lot more pressure than the inflator and still no signs of a leak.
Ive refitted the breather pipes with a little threebond and will put the bike back together. Im going to invest in one of those boroscope kits that work on a mobile phone and hopefully Ill be able to use it through either the timing hole or remove the starter motor and go through there.
Unless and until I get positive proof of the flange gasket failing Im not removing the flange. Fingers crossed it was a breather pipe leak all along.

[Tom H]

Hopefully you have not put the bike back together yet.

In you pic, the bell housing looks like there is no oil leak to me except near the cam plug. The bottom of the bell housing looks clean. Did you clean up the mess before taking the pic???

When you used the air pressure (I do not know how much pressure I used since I used my compressor, 15 or 20psi??) and the soapy water. Did you use a cup and a very wet/dripping off paint brush or the like to dab around the flange gasket and all the bits?? Spray bottle? You need to get the suspected ares very wet.

With as clean as the bell housing is at the bottom, I can't believe there is a leak on the engine side. How is the trans input seal?

As mentioned, the breather hoses can cause the look of a leaking cam plug, Are you sure they are not cracked and that the hose clamps are tight?

I have found that the bearing carrier bolts can come loose, well the don't loosen, but the gasket compresses and now the bolts are not clamping like they should. If your not going to change the gasket, at least torque the bolts up.

FWIW: if you need to do the rear main seal, it can be carefully removed and installed without pulling the carrier.

Hope this helps some,
Tom

[Stevex]

Thanks for your input Tom.
The photo was taken before I cleaned the bell housing. Most accumulated oil was either side of the cam bung on top of the flange housing. I used a specialist leak detector spray and throughly soaked the whole area. This stuff will indicate the minutest leak.
I checked the gearbox input side too and it was dry. I previously replaced the original seal with a viton one.
Im left presuming the leak did come from one of the breather tubes. Ive inspected them and there are no splits etc.
Checking the torque on the flanges bolts is an idea as Im waiting for some schnoor washers before rebuilding the flywheel and clutch. What is the torque setting in nm please?

[Tom H]

Bearing carrier 22Ft/lbs. Flywheel 30ft/lbs. Ring gear 22ft/lbs.  You can bump these numbers up about 2ft/lbs without worry.

If you change out the bolts or washers on the bearing carrier use wave washers not schnoor.

Tom