Oil Leak - From rear main seal ...

Gutted at 15,000 miles the GRiSO has developed an oil leak.  Tried to locate it but couldn't find the source. The leak would only occur when the engine was running forming a drip on the rear left of the oil sump every 30 seconds at tick over.   I noticed that there was a drip formed on the started motor cover also.

Cleaned the sump and all round the gasket and completely sure the leak was not from the bottom sump gasket. Oil level was still ok (half way up dipstick.

The bike had been serviced 3 months ago and had not dropped any oil.

Left the bike with the local MG dealer. Yesterday got a call to say that the inside of the started motor cover was wet with oil and that leak was from the main rear seal.  Advised that the seals need replaced and that MG advise the clutch should be too if any oil present there. Grisoless for the foreseeable ... world of pain for my wallet!!

Not 100% sure they have seen where the oil is leaking from and will call them to confirm. Curious if anyone might have thoughts on another likely source....I may just be grasping at straws here.

Cheers,

Angus.

Angus, mine did this intermittently for years - seems to have stopped for now. Only thing I did was replace both the sump gaskets and remove, clean and re-tighten the oil feed at the back of the sump. I too, thought I had a rear main seal gone and was prepared to swear a little (OK I did, and a lot).

Maybe, just maybe...

Others will be along shortly to comment

Angus, what year is yours? Sorry, I know I always ask this but there were issues associated with various years. I really doubt it's the rear main seal, if it is you are really unlucky. Even if the clutch friction plate is soiled all it should need is a plate and grind if needed, (Probably not!). Shit, Michael and I would have this turned over in four days max as long as we had the parts. Months? Fuck off! Who are these idiots! Remember both Michael and I are working six hours a day, (On the tools.) max.

Pete

Angus i had the same thing, it went back three times!

I was told that there were different seals and as i had new crankcases it needed a different seal, but took three attempts to find which one I have to say that after the third attempt (which from memory did away with a seal altogether) it has been leak free ever since (18,000 miles)

I am sure there are people on here who will be able to make sense of the different seals (or i was strung along with a line at the time!) but if there are differences it might help you/your mechanic.

I was not too worried at the time as it was under warrenty

Hi Pete,

The bike is a 2008 1200 8v. The MG dealer (only one in Scotland) sell MG, Yamaha, Piaggio and Aprilia.

They only have one tech who specialises in MG. To be fair to the guy they are really busy, he has said he can't see him getting to my bike in the next couple of weeks after which he is on holiday for 2 weeks. So he advised it will be after that. He did say he might be able to save the clutch but would want to see it before confirming this.

Cheers,

Angus.

Tell them to go to the Servicemotoguzzi website and look at the bloody tech bulletins for the period.

Some early 8V's had a problem, (Mine never did.) caused by poor machining of the rear main bearing flange which left the small oil dowel sitting so proud of the flange that it bottomed out on the register in the crank case. This, coupled with the fact that on some motors the two bottom flange bolts were too long, or, the threads and holes in the crankcase weren't deep enough, means that when the bolts are done up they don't crush down well enough to seal the bottom of the flange.

The answer is simple but the instructions MUST be followed to the letter.

Once the gearbox and clutch are off the rear flange has to be pulled.

Then all traces of the gasket must be removed from both flange and case.

Now the oil feed dowel needs to be filed down so it's 1-2mm shorter. Make sure NO debris is left in the oil gallery.

Reinstall the flange with a new o-Ring on the dowel WITH NO GASKET, GET IT? NO GASKET! but the flange sealed with a thin smear of Threebond 1211.

The two bottom bolts should be replaced with ones 5mm shorter.

If a gasket is used it WILL leak again, no ifs or buts, it will leak!

The above procedure if carried out correctly WILL cure the problem, first time, every time. If your shop chooses to ignore these instructions your gear box will be in and out like a rabbit's cock on the vinegar stroke until they get it right.

Pete

Pete,

Your knowledge is amazing. I will pass on the info to the tech. He will be grateful for it I am sure.

Thanks again!

Angus.

Hey Sid,

I wonder if your bike had the problem Pete has highlighted.

Pete,

I spoke to the tech and sent him an email with your advise, as I thought he was grateful of the input. Last thing he wants is the bike in and out the workshop for the same thing.

Thanks again!

Angus.

See i knew someone would be able to explain what needed to happen :-)

Yes that is what happened to mine too, they tried with the gasget and without and then all the things that Peter said and it worked!

Pete:

Could you post the relevant Service Bulletin, please?

Here's my "production" after a fast commute to Vancouver, BC from Seattle:

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Thanks!

JL

Pete Roper wrote:

Tell them to go to the Servicemotoguzzi website and look at the bloody tech bulletins for the period.

Some early 8V's had a problem, (Mine never did.) caused by poor machining of the rear main bearing flange which left the small oil dowel sitting so proud of the flange that it bottomed out on the register in the crank case. This, coupled with the fact that on some motors the two bottom flange bolts were too long, or, the threads and holes in the crankcase weren't deep enough, means that when the bolts are done up they don't crush down well enough to seal the bottom of the flange.

The answer is simple but the instructions MUST be followed to the letter.

Once the gearbox and clutch are off the rear flange has to be pulled.

Then all traces of the gasket must be removed from both flange and case.

Now the oil feed dowel needs to be filed down so it's 1-2mm shorter. Make sure NO debris is left in the oil gallery.

Reinstall the flange with a new o-Ring on the dowel WITH NO GASKET, GET IT? NO GASKET! but the flange sealed with a thin smear of Threebond 1211.

The two bottom bolts should be replaced with ones 5mm shorter.

If a gasket is used it WILL leak again, no ifs or buts, it will leak!

The above procedure if carried out correctly WILL cure the problem, first time, every time. If your shop chooses to ignore these instructions your gear box will be in and out like a rabbit's cock on the vinegar stroke until they get it right.

Pete

I'm no longer an 'Official' service agent and no longer have access to the Servicemotoguzzi page so I can't post it up. Doing so was frowned upon anyway as apparently Piaggio don't like their paying customers knowing anything about what they've paid good money for.........

Pete

Thanks very much, Pete.

As usual, your assistance much appreciated.

After a fair bit of the Dealer fighting my corner with Piaggio the bike had been fixed and they gave parts under warranty. The parts included a new flange, if I understand correctly this was replaced to allow the correct space for the O ring.

Bike home, running sweet. Was great to get back out on her, cold 4'C ride today.

Thanks again for the support from you guys and for Petes expert advice!

Angus.

That's good news Angus!
That flange leak and the flat tappet are the two things that plagued the early GRiSO.
You addressed both of those issues so now you're good. Go on a bunch of rides and give it the berries!!

[You must be registered and logged in to see this image.]
REAR MAIN BEARING PULLER TOOL BIG TWINS 1967 TO 2018 GU12913600. $42 at MG Cycle. Made removal of bearing carrier a snap.

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Based on wetting pattern. I believe this is the culprit. It receives a hollow dowel and o-ring feeding oil to the rear main bearing through carrier.

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2 lower bolts are reported to be too long in some cases, so I bottomed all the bolts by hand and measured between crankcase and bolt head to verify. Clearance ranged from 9.10mm to 8.76mm.

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Washer: 0.77mm. Gasket remnant (not shown): 0.40mm.

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Carrier Flange: 7.99mm

Total thickness of carrier flange, washer and gasket = 9.16mm. Conclusion: ALL THE BOLTS ARE TOO LONG for a good clamp!!

Furthemore, I intend to delete Paper gasket and proceed with ThreeBond only as Pete advises; which may make things worse. Stock bolts, carrier to crankcase, are M8-1.25X25mm. Easily sourced shorter bolts at local hardware store but was hesitant to change all 8 bolts to 20mm length so ended up grinding 2mm off each stock bolt. Total PIA.

Excellent work! I unfortunately had to undertake this same task on my '17, similarly checking all the things (in my case, the o-ring groove was machined too deeply, and the stock o-ring itself appeared to be very poor quality).

Yeah, even after a few decades spent doing this kind of work professionally on old European cars, I found this job to be a slightly tedious PITA. I hope I never have to do it again, as by that point enough time will have elapsed that I'll have forgotten all the insight that would have made subsequent encounters more expedient.  [You must be registered and logged in to see this image.]