Author Topic: Moto Guzzi Convert Oil Leak  (Read 2031 times)

Offline agarcia323

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Moto Guzzi Convert Oil Leak
« on: March 29, 2026, 05:03:42 PM »
I have a 77 Convert.  I had it serviced back in November, and it leaked all the oil out through the timing adjustment hole.  This was I was riding it.  I stored it for winter and just replaced the rubber cover.  It is still dripping out from that hole. I bought two different plugs.  Any thoughts?  So far I've put like 10 miles on it and have not had it dump out again. 

Offline Tom H

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Re: Moto Guzzi Convert Oil Leak
« Reply #1 on: March 29, 2026, 05:47:34 PM »
That rubber plug is just a cover, it's not there to hold oil in.

I can't tell you why you had oil in the bell housing, but I would highly suggest checking the engine oil using the dipstick on the left hand side of the engine and checking the transmission fluid level in the oil tank on the left hand side of the bike just below the seat. Make sure there is a proper amount of oil in each. Engine oil in the engine and ATF (not sure what type) in the trans oil tank.

Good luck!
Tom
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Re: Moto Guzzi Convert Oil Leak
« Reply #2 on: March 29, 2026, 06:24:39 PM »
Check with the place that did the service.  How experienced is that technician with Guzzi?  The torque converter chamber is dry air and no reason for oil to come out of the timing inspection hole.  It sounds a lot like someone put oil in the wrong place.  Meanwhile what is the status of the engine or transmission where that oil was supposed to be replaced?

Patrick Hayes
Fremont CA

Online Dave Swanson

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Re: Moto Guzzi Convert Oil Leak
« Reply #3 on: March 29, 2026, 07:22:48 PM »
I agree with Patrick.

Where did you find a shop that is familiar with Convert service requirements?  I would wager that you can count the number of shops competent to service a Convert nowadays on one hand. 
Dave Swanson - Northern IL
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Offline agarcia323

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Re: Moto Guzzi Convert Oil Leak
« Reply #4 on: March 29, 2026, 07:37:21 PM »
All the repairs were done at Harpers.

Offline guzzisteve

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Re: Moto Guzzi Convert Oil Leak
« Reply #5 on: March 29, 2026, 08:07:01 PM »
   Contact Ace in St Joe for best service
« Last Edit: March 29, 2026, 08:12:31 PM by guzzisteve »
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Online Dave Swanson

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Re: Moto Guzzi Convert Oil Leak
« Reply #6 on: March 29, 2026, 09:28:49 PM »
All the repairs were done at Harpers.

Well you're in luck.  They certainly know their way around a Convert.   But it is very mysterious what transpired.
Dave Swanson - Northern IL
1935 GTS
1968 V700
1973 V7 Sport
1974 Eldo
1974 Police Eldo
1976 Convert
1977 Lemans 1.2
1980 T3 California
1993 1000S - Sparklehorse
1998 V11 EV HDM
2004 V11S - Eraldo-ized
2016 Griso SE - Beetle-ized
2021 V7-850 Stone Centenario
2022 V85TT
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Offline guzzisteve

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Re: Moto Guzzi Convert Oil Leak
« Reply #7 on: March 30, 2026, 09:42:30 AM »
You may have a stuck crank pressure relief valve, this would blow out the rear main seal. It is in large pipe going down through bell housing under air box. If you still have an airbox. It has a big round ball bearing in it that gets flat spots on it & gets stuck. Especially if you have mayonnaise in oil from moisture in oil. This happens if you ride in cold weather till bike gets good & hot. To fix seal you have to pull transmission. Check oil level with dipstick on LH side of motor, right above sidestand. Fill till at top mark when screwed in.
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Online TN Mark

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Re: Moto Guzzi Convert Oil Leak
« Reply #8 on: March 30, 2026, 02:25:54 PM »
Well you're in luck.  They certainly know their way around a Convert.   But it is very mysterious what transpired.

Just another data point that justifies why most dealers won't do anything on a bike that's over 10 years old. A YouTube guy touring on a Honda Goldwing needed a new front tire. The Honda dealer would change the tire, but only if the owner brought in the wheel, off the bike. The Honda dealer wouldn't remove the front wheel because of the age of bike.

Offline Bulldog9

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Re: Moto Guzzi Convert Oil Leak
« Reply #9 on: March 30, 2026, 02:44:29 PM »
I have a 77 Convert.  I had it serviced back in November, and it leaked all the oil out through the timing adjustment hole.  This was I was riding it.  I stored it for winter and just replaced the rubber cover.  It is still dripping out from that hole. I bought two different plugs.  Any thoughts?  So far I've put like 10 miles on it and have not had it dump out again.

Unlikely it dumped the oil out of the inspection hole. The flywheel case (for lack or a better word) is just that a case. Inside is the torque convertor/flywheel plate and starter ring.

As others have said, you may have a blown rear main seal. That said, there is a weep hole at the bottom that will let anything that leaks from TC or RMS. My Convert leaves little drops marking its territory, but is not worth tearing down or into as it is smaller than a dime, and only occasionally.

Losing that much oil must have been a mess, and I hope you didn't ride or run it long if it really dumped all its engine oil. Are you sure is was motor oil and not the trans fluid?

If you are not semi skilled, have a tech take a look at it and find where you are leaking your oil from.  Harpers is a good shop, they will tell it to you straight and fix your issue.
« Last Edit: March 30, 2026, 05:20:35 PM by Bulldog9 »
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The Living: 1976 Convert, 2007 GRiSO, 2012 Norge GT, 2016 Stornello #742, 2023 V85 TT
The Departed: 2017 MGX, 2014 Norge GT, 2004 Breva 750, 2008 1200 Sport
In Stasis: 1978 XS750, XS1100SF

Offline guzzisteve

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Re: Moto Guzzi Convert Oil Leak
« Reply #10 on: March 30, 2026, 04:28:36 PM »
Around 2000 I was on my way to BobJoe Cycle in Sycamore, IL, when I pulled up there was a trail behind me. Got done w/business and priced oil, $5 a qt . Took off for home 7mi, coming down hill in Kingston in front of my place the lifters started rattling. I had 1/2 Qt in crankcase. Never replaced the seal, clutch not effected, comes out the slot hole.  I'm still riding on the same seal 26yrs later, it just leaks a quarter size when parked. I don't like wrenching on my own stuff, it only costs $$$, and they need alot.
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Re: Moto Guzzi Convert Oil Leak
« Reply #11 on: March 30, 2026, 05:03:19 PM »
Unlikely it dumped the oil out of the inspection hole.

We're going with what the OP wrote in his complaint.  He wrote "...and it leaked all the oil out through the timing adjustment hole."  I don't know of any other holes where one could inspect or adjust timing other than the rubber plug on the right side of the bell house.  I agree it is very odd, but that is the data we have from the owner.

I sure hope he reports back with the inspection and resolution results.

Patrick Hayes
Fremont CA

Offline guzzisteve

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Re: Moto Guzzi Convert Oil Leak
« Reply #12 on: March 30, 2026, 05:50:27 PM »
Maybe it has a light weight flywheel mount & it cracked that went in to the bowl. Never seen one do that, but it could happen depending on flaws in the metal. How else would you get spraying to the plug. Never seen that. Maybe the hole on bottom of bell housing it plugged.
This stuff hurts my brain, last worked on a convert 25yrs ago right before I moved. I had to put a HD flywheel in one cause it broke the light weight one.
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Offline chuck peterson

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Re: Moto Guzzi Convert Oil Leak
« Reply #13 on: March 31, 2026, 07:05:57 AM »
If you’re a customer of Harper’s, keep being a customer of theirs and call them. They most likely want to figure it out for you. You do have a major issue that warrants professional help.

If it’s red it’s Automatic transmission fluid. If it’s dark it’s likely oil from the motor. I wouldn’t ride it until the problem is sorted out.

Give them a call
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Offline TOMB

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Re: Moto Guzzi Convert Oil Leak
« Reply #14 on: April 05, 2026, 08:32:47 PM »
Chuck Peterson used to monitor his convert leaks after his rebuild by placing a white doyly under the torque converter area of his bike.
worked quite well.

Chuck is a good source for info on converts also

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